Hallicrafters SR-400 CYCLONE II User manual

REPAIR AND RESTORATION OF THE SR-400
1
WDØGOF 6/22/20014
REPAIR & RESTORATION
OF
HALLICRAFTERS
SR-400 CYCLONE II
SR-400A CYCLONE III
CAUTION: FATAL VOLTAGES ARE OPEN AND EXPOSED ONCE
THE COVERS OR CASE IS REMOVED. OBSERVE THE FREE
HAND RULE. THAT IS, ANY TIME THE POWER IS APPLIED, IF
YOU ARE RIGHT HANDED YOUR LEFT HAND IS IN YOUR HIP
POCKET. IF YOU ARE LEFT HANDED YOUR RIGHT HAND IS
IN YOUR HIP POCKET. YOU PROCEED AT YOUR OWN RISK.
This document is the intellectual property of the author, Walter A. Cates, WDØGOF, unless specifically
credited to a contributor. All processes, ideas, drawings, data sheets and opinions contained here-in are the
intellectual property of the author. Any reproduction of this document for profit will be vigorously pursued.

REPAIR AND RESTORATION OF THE SR-400
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WDØGOF 6/22/20014
INTRODUCTION
This is not a “restore to museum” quality guide. Cleaning, painting and front panel touchup are not covered.
There are reams of documents that cover those actions. There are very few documents that delve into the inner
workings of these radios. This does. This document applies only to the Cyclone II and Cyclone III. The first
question you might ask is “why did I not include the SR-400 Cyclone”? The first generation 400 had too many
things not quite correct. Mr. Orwin (Hallicrafters engineer) fixed those when he designed the Cyclone II. The
best advice I can offer to owners of the original SR-400 is to upgrade it to the Cyclone II level. A document for
upgrading a Cyclone to the Cyclone II is available. Contact me and I will send you the document. Just to clear
the air I am not a fan of the Cyclone III either. I use my Cyclone II. I turn on my Cyclone III once a month for 2
or 3 hours just to keep it dry.
This document takes a systematic approach to rehab. Unless otherwise noted all discussions apply to either the
Cyclone II or III. It is designed to be used in conjunction with the original equipment manual. In all discussions
the word manual refers to:
OPERATING AND
SERVICE INSTRUCTIONS
FOR
COMMUNICATIONS
TRANSCEIVER
MODEL SR-400(X)
If this procedure is followed, in the order presented, you will minimize the frustration of restarts and backups
and chasing red herrings. It assumes a working knowledge of radio and tube circuit theory. For the most part it
will lead you to the stage or stages where faults have occurred. At this point you must have the skills to locate
the failed component. Each step of this process assumes all proceeding steps have been successfully completed.
If you try to jump into the middle of the process you may end up in confusion.
You have obviously elected to spend time and effort in this restoration. So, I high y recommend that you
do a dry run with the schematic, manual and this document. As you read this document follow it through the
schematic and the manual. A wealth of knowledge will be gained by doing so.
This document is the intellectual property of the author, Walter A. Cates, WDØGOF, unless specifically
credited to a contributor. All processes, ideas, drawings, data sheets and opinions contained here-in are
the intellectual property of the author. Any reproduction of this document for profit will be vigorously
pursued.
CAUTION: FATAL VOLTAGES ARE OPEN AND EXPOSED ONCE
THE COVERS OR CASE IS REMOVED. OBSERVE THE FREE
HAND RULE. THAT IS, ANY TIME THE POWER IS APPLIED, IF
YOU ARE RIGHT HANDED YOUR LEFT HAND IS IN YOUR HIP
POCKET. IF YOU ARE LEFT HANDED YOUR RIGHT HAND IS
IN YOUR HIP POCKET. YOU PROCEED AT YOUR OWN RISK.

REPAIR AND RESTORATION OF THE SR-400
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WDØGOF 6/22/20014
TABLE OF CONTENTS
INTRODUCTION .................................................................................................................................................. 2
1. SR-400 INITIAL INSPECTION AND TESTING............................................................................................. 5
1-1. VISUAL AND MECHANICAL INSPECTION......................................................................................... 5
1-2. RECAPPING;.............................................................................................................................................. 5
1-3. AFTER MARKET MODIFICATIONS ...................................................................................................... 5
1-4. INITIAL POWER UP ................................................................................................................................. 6
1-4-1. TEST EQUIPMENT REQUIRED ....................................................................................................... 6
1-4-2. POWER UP PRE-SET CONDITIONS................................................................................................ 6
1-4-3. INITIAL POWER UP TESTS ............................................................................................................. 6
1-5. CHECK AND ADJUSTMENT OF OSCILLATORS: ............................................................................... 7
1-5-1 TEST EQUIPMENT REQUIRED ........................................................................................................ 7
1-5-2. CARRIER OSCILLATOR:.................................................................................................................. 7
1-5-3. HETERODYNE OSCILLATOR:........................................................................................................ 7
1-5-4. VFO:..................................................................................................................................................... 8
1-5-4-1. RIT/CAL....................................................................................................................................... 8
1-5-4-2. VFO CORRECTOR...................................................................................................................... 8
1-5-4-3. VFO ALIGNMENT...................................................................................................................... 8
2. RECEIVER FAULT ISOLATION................................................................................................................... 10
2-1. EQUIPMENT REQUIRED....................................................................................................................... 10
2-2. STANDARD TEST CONDITIONS ......................................................................................................... 10
2-3. PROCEDURE OVERVIEW & PRESET CONDITIONS ........................................................................ 10
2-4. RECEIVER FAULT ISOLATION CHART............................................................................................. 11
2-5 AGC TEST ................................................................................................................................................. 12
2-5-1. AGC FIGURE OF MERIT ................................................................................................................ 12
2-5-2. AGC THRESHOLD ADJUSTMENT ............................................................................................... 12
2-6. S-METER ZERO....................................................................................................................................... 12
2-7. CAL OSCILLATOR ................................................................................................................................. 12
2-7-1. CYCLONE II TEST........................................................................................................................... 12
2-7-2. CYCLONE III TEST ......................................................................................................................... 12
3. TRANSMITTER TESTING............................................................................................................................. 13
3-1. TEST EQUIPMENT REQUIRED ............................................................................................................ 13
3-2. STANDARD TEST CONDITIONS ......................................................................................................... 13
3-3. BIAS ADJUST .......................................................................................................................................... 14
3-4 INITIAL TRANSMITTER TESTS............................................................................................................ 14
3-4-1 TRANSMITTER POWER TEST ....................................................................................................... 14
3-5, TRANSMITTER FAULT ISOLATION ................................................................................................... 15
3-5-1, DRIVER CAPACITIVE PICKUP TOOL ......................................................................................... 15
3-5-2, LOW OR NO POWER ACROSS ALL BANDS .............................................................................. 16
3-5-3, NO OR LOW POWER ON A SINGLE BAND. ............................................................................... 16
4. SUBSYSTEM TROUBLESHOOTING AND TESTING................................................................................ 17
4-1 VFO DRIFT................................................................................................................................................ 17
4-2. V15 RX FAULT ISOLATION.................................................................................................................. 17
4-3. V9B RX FAULT ISOLATION................................................................................................................. 17
4-4. V9A RX FAULT ISOLATION................................................................................................................. 17
4-5. V7A RX FAULT ISOLATION................................................................................................................. 17
4-6. XTAL RX FILTER/NOTCH FAULT ISOLATION ................................................................................ 17

REPAIR AND RESTORATION OF THE SR-400
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4-7. V6 RX FAULT ISOLATION.................................................................................................................... 17
4-8. V4A RX FAULT ISOLATION................................................................................................................. 18
4-9. V3 RX FAULT ISOLATION.................................................................................................................... 18
4-10 V2 RX MIXER FAULT ISOLATION..................................................................................................... 18
4-11 V1 RX FAULT ISOLATION................................................................................................................... 18
5. TECH NOTES .................................................................................................................................................. 19
5-1. BASIC TUNE UP...................................................................................................................................... 19
5-1-1. THE PROBLEM: ............................................................................................................................... 19
5-1-2. WHY IS THIS IMPORTANT?.......................................................................................................... 19
5-1-3. A SIMPLE SOLUTION..................................................................................................................... 19
5-1-4. SUMMATION: .................................................................................................................................. 19
5-1-5. MANUAL SECTION 5-4 MARK UP:............................................................................................... 20
5-2 PA NEUTRALIZATION ........................................................................................................................... 22
5-3. OPTIONAL 6 MEG IF ALIGNMENT ..................................................................................................... 23
5-x. ADDITIONAL TECHNICAL INFORMATION SOURCES:.................................................................. 23
6. DATA SHEETS................................................................................................................................................ 24
6-1. VFO FREQUENCY CORRECTION........................................................................................................ 24
6.2 PERFORMANCE DATA........................................................................................................................... 25
6-2-1. RECEIVER PERFORMANCE DATA.............................................................................................. 25
6-2-2. TRANSMITTER PERFORMANCE ................................................................................................. 26

REPAIR AND RESTORATION OF THE SR-400
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1. SR-400 INITIAL INSPECTION AND TESTING.
SO YOU JUST GOT AN SR-400 FROM E-BAY OR SOMEONE THAT
SAID “IT WORKED FINE THE LAST TIME I TURNED IT ON”. NOW
WHERE DO YOU START? THE FOLLOWING PROCESS HAS
EVOLVED OVER YEARS OF REFURBISHING THE SR-400. IT
SHOULD BE FOLLOWED IN THE ORDER IT IS WRITTEN. THIS
PROCEDURE IS DESIGNED TO PROGRESS IN AN ORDERLY
MANNER TO MINIMIZE RUNNING IN CIRCLES. YOU MUST HAVE
THE MINIMUM OF TEST EQUIPMENT LISTED TO PROPERLY
REHAB OR REPAIR THIS EQUIPMENT. BE AWARE THIS IS NOT
SOMETHING THAT WILL BE ACCOMPLISHED WITH GREAT SPEED.
THE AVERAGE TIME TO COMPLETION IS AROUND 60 HOURS.
SOME HAVE TAKEN AS MUCH AS 200 HOURS, SOME AS FEW AS 20
HOURS.
1-1. VISUAL AND MECHANICAL INSPECTION
Complete chassis cleaning and mechanical inspection are always advised. Cleaning of the controls, rotary
switches and the relays is of particular importance. Look closely for broken or burned components. Check the
rotation of the controls and mechanical stops of the main tuning dial (Section 8-8-A in the manual). Try to
eliminate the mechanical problem first. If you are going to upgrade to a higher production run complete those
upgrades before you start the electrical tests.
1-2. RECAPPING;
There are only six capacitors that are considered must replace components. They are: C70 and C218, 5 uf/25v;
C46, 25 uf/25v; C147, 2 X 30 uf/350v; C240, 175 uf/25v and C244, 500 uf/6v. C240 and C244 are found only
in the SR-400A. Capacitor C147 carries a heavy current load. Therefore the ESR rating of its replacement is
important. They should have an ESR rating of 1.0 ohm or less. ESR’s less than 0.3 ohm are available. This is
not a place to save money. C147 is a dual cap. There are sources for this capacitor, but be careful. Some
manufactures of these parts use inexpensive low quality parts. Don't buy from suppliers who will not quote or
guarantee the ESR rating. Very low ESR individual capacitors are readily available. So replacing the dual cap
with two capacitors under the chassis is sometimes a better solution. Generally speaking shotgun replacement of
the paper caps is not recommended at this stage of refurbishment.
1-3. AFTER MARKET MODIFICATIONS
If you find any modifications, re-wirings or added components remove them and return the rig to the original
configuration. For valid circuit modifications see k9axn in section 5-3.

REPAIR AND RESTORATION OF THE SR-400
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1-4. INITIAL POWER UP
Note: When bench testing the SR-400 set the antenna switch (S2) to SEPARATE. Connect the load and
wattmeter to ANTENNA (J1 or J2). Connect the signal generator to REC ONLY (J3). This will eliminate the
possibility of transmitting into the signal generator. It will also speed up the transition from RX to TX while
testing.
1-4-1. TEST EQUIPMENT REQUIRED
DVM or VTVM
1-4-2. POWER UP PRE-SET CONDITIONS
First and of critical importance, you must have a power supply that has been tested and meets all the original
specifications. You will not be transmitting power until late in this process so temporarily replace the 5 amp slo-
blow fuse with a 4 amp normal delay fuse. It is not necessary to start with a low AC voltage and increase the
voltage over time to cook the rig. There are no domino circuits in the SR-400. If you have a short somewhere,
you may cook a resistor and it will smell bad but it will lead you straight to the problem. So, set all the gain
and drive controls to minimum. Every time you turn on your SR-400 all these controls should be at minimum.
The STANDARD PRE-POWER UP CONFIGURATION will always be: all gain controls set to minimum,
RIT off, RIT CONTROL at mid-range, CAL ADJ at mid-range, CAL OFF, NOISE BLANKER OFF, NOTCH
pressed in and fully counterclockwise. Preset the PRESELECTOR to the approximate position in the band you
will be operating, set the LOAD and PLATE tuning to the appropriate settings corresponding to the chart in the
original manual (the chart is located in section 5). Set the FUNCTION switch to either USB or LSB depending
upon which band you will be testing the default is LSB. Insure that a jumper plug in installed in J4 on the rear
of the radio. The jumper plug should have a jumper between pins 4 and 10.
CAUTION: FATAL VOLTAGES ARE OPEN AND EXPOSED ONCE THE COVERS OR CASE IS
REMOVED. OBSERVE THE FREE HAND RULE. THAT IS, ANY TIME THE POWER IS APPLIED, IF
YOU ARE RIGHT HANDED YOUR LEFT HAND IS IN YOUR HIP POCKET. IF YOU ARE LEFT
HANDED YOUR RIGHT HAND IS IN YOUR HIP POCKET
1-4-3. INITIAL POWER UP TESTS
Ok it is time apply power. It is assumed that you have a fully recapped power supply that meets all
specifications. Attach the power supply and plug it in. Set the operation switch to REC ONLY. If it blows the
fuse you most likely have a short in the hi-voltage or the B+ locate the fault and repair before continuing. Now
let it sit there for 10 to 15 minutes. Locate R50, 2000 ohm, 10 watt resistor connected to V10. The voltage at
one end should 150vdc and 250 – 280vdc at the other if not; you have a fault in the wiring or the 150v regulator.
This fault must be cleared before you proceed. Otherwise the only thing we need to do at this time is rough set
the bias voltage. Some models of the PS-500 power supplies have a bias control on the rear of the chassis. If
yours has the bias control pot, proceed to Abelow. If it doesn’t, go to B.
A. On the underside of the Final tubes locate the grid side of R107 (100k). This is where we will measure the
bias voltage in the receive mode. Set your meter on the 200vdc range. Now adjust the bias adjust control on the
power supply for maximum negative voltage. Continue to step B.
B. Turn the power off; plug your meter into the red (+) and blue (-) test jacks on the power supply. Set the
meter on the 2vdc range. Set the function switch to LSB, Connect a mic and set the RF GAIN and MIC GAIN
to minimum. Turn the power back on. Let it warm up. Set the OPERATION switch to MOX. Key the mic.
Adjust the BIAS ADJ control on the front panel for 0.7 vdc on the test meter. If you cannot adjust it or it is very
high then you have a problem in the final PA or bias divider and this must be corrected before you proceed. If
all is well with the bias you are now ready to proceed to the CHECK AND ADJUSTMENT OF
OSCILLATORS section.

REPAIR AND RESTORATION OF THE SR-400
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1-5. CHECK AND ADJUSTMENT OF OSCILLATORS:
Before starting any receiver or transmitter troubleshooting or the RF or I.F. alignment it is imperative that the
xtal oscillators and the VFO are precisely on frequency. If you will devote the time to these considerations you
will be rewarded with a rig that performs as well as any modern rig. A frequency counter and scope are
required. The procedure in the book will work ok, but will compound errors. If you get all the oscillators “on
freq” with proper output levels individually, then all else will fall into place. Do not make any adjustments until
the rig has been on for at least 30 minutes. Optimize the VFO last to insure it is stable. Do not hurry. Take your
time, these processes are critical.
1-5-1 TEST EQUIPMENT REQUIRED
Oscilloscope, 100MHz bandwidth and two probes, Frequency counter.
1-5-2. CARRIER OSCILLATOR:
The carrier oscillator is comprised of V14A and its associated circuitry. First thing is to check the output of the
carrier osc in both USB and LSB modes. After warm up you should have approximately 6 vpp on pin 8 of
V9A. Now adjust T4 for max. The voltage on pin 4 or 3 of T4 should be 8 Vpp. If these voltages are more than
15% low then you most likely have a fault in the oscillator and this fault must be corrected before you proceed.
Once you are satisfied with the oscillator output set the function switch to USB. Connect a scope to pin 8 of
V9A to monitor the output voltage of the osc. Connect the frequency counter to either pin 4 or 3 of T4.
You will find that if you adjust T4 in one direction from the peak the signal drops off very fast. In the other
direction it falls more slowly. T4 should be adjusted about 2% to 5% off peak toward the slow fall off side.
Switch back and forth from USB to LSB to insure both oscillators start without any hesitation. In USB mode
adjust C139 for exactly 1652.800 KHz. Switch to LSB mode and adjust C136 for exactly 1650.000 KHz.
Adjustment of T4 and C136 and C139 can interact. Re-check the output voltage and re-check the frequency
back and forth several times to insure that everything is stable and there is no hesitation in the oscillator startup.
1-5-3. HETERODYNE OSCILLATOR:
The Het Osc is comprised of V12 and its associated circuitry. This oscillator is the most troublesome of the
three. There are no adjustments to pull the frequency of each xtal. So if you do not have a box of spare xtals you
are rather limited in what you can do to put it precisely on frequency. First thing, check the oscillator output.
Connect the scope to pin 8 of V2. The minimum peak to peak voltages for each band should be: 80 meters 4
Vpp, 40 meters 4 Vpp, 20 meters 2.5 Vpp, 15 meters 2.5 Vpp, 10 meters (all 4 bands) 2 Vpp. If the output does
not meet these minimums this fault must be cleared before proceeding. Once you are satisfied with the
oscillator output signal levels, disconnect the scope and connect the frequency counter to pin 8 of V2A and
check the frequency on each band. If the xtal frequencies are all high or all low then swapping out C104 and/or
C105 may bring them back in spec. With the four 10 meter xtals you are pretty much stuck with where ever
they are unless you have a bag of xtals to swap. For the 80, 40, 20 and 15 meter bands, each band has a loading
cap (C103, C102, C101 and C100 respectively). These loading caps can be swapped out to pull individual xtals
on to frequency. The end unit frequency spec is + or – 3 KHz at any dial point across any band. With the VFO
and Carrier oscillators dead on whatever error you have in the heterodyne oscillator is what you will have to
live with. The use of the CAL ADJ and RIT CONTROL adjustments will be discussed later to compensate for
errors in the het osc.

REPAIR AND RESTORATION OF THE SR-400
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1-5-4. VFO:
The VFO is comprised of V13, V4B and associated circuitry, the VFO correction circuitry and the RIT/CAL
circuitry.
From the manual:
Frequency Stability;
Less than 250 cycles drift in the first hour, after a fifteen minute warm-up, and
less than 100 cycles per hour thereafter.
Due to the age of the SR-400 a more reasonable warm up time is 30 to 40 minutes.
1-5-4-1. RIT/CAL
The RIT/CAL ckts are used to change the bias voltage on a varicap in the VFO. This is used to make minor
corrections to the VFO frequency. In cw mode with the RIT turned on the RIT CONTROL functions as the
BFO.
Set the RIT lever switch to off, adjust the RIT control to the center of its rotation. Set the CAL control to the
center of its rotation. This is the setting for these controls throughout all testing unless otherwise noted. Set the
main tuning to 300 on the black scale. Connect the frequency counter to pin 3 of V4A. Fine tune the main
tuning for 4550.0 on the counter. Rotate the CAL control to max ccw and note the counter reading. Rotate the
CAL max cw and note the counter reading. The difference from ccw to cc rotation should be minimum 4 KHz;
most rigs will run approximately 6 KHz. Readjust the CAL pot for 4550 Hz on the counter. Turn the RIT on.
Adjust the RIT CONTROL for 4550Hz on the counter. The RIT CONTROL should be at the center of its
rotation and not more than 10 to 15
o
off the center of its rotation. If it is off too far then you have a dirty switch
(S7) or a fault in the voltage divider network. Clear this fault before proceeding. When the RIT CONTROL is
rotated min to max you should see the same swing in frequency as when you rotated the CAL control earlier.
1-5-4-2. VFO CORRECTOR
The VFO correction ckt adjusts for the frequency off set between USB and LSB (NOTE: CW operates in the
USB MODE). Before the VFO is aligned it must be established that the correction ckts are working properly.
Connect the frequency counter to pin 3 of V4A. Set the function switch to LSB, 40 meter band and tune the
main tuning until the frequency counter reads 4.5530 MHz. Switch to USB and the frequency should drop 3000
Hz or to 4.5500 MHz. If not adjust C127 for exactly 4.5500. If you cannot then there is a fault in the corrector
ckt that must be repaired before you can continue with the VFO alignment. There are only 5 possibilities for this
fault. First check the offset switching voltage on pin 4 of J4 (the ACCESSORY PLUG). In USB it should be
150 vdc. In LSB it should be a negative voltage in the range of -20 to -28 vdc. If the offset switching voltage is
correct and the offset is un-settable then R85 is possible but least likely. CR12, C126 and/or C127 are most
likely the cause. If the offset voltage is incorrect the most likely cause is the FUNCTION switch S3A. This fault
must be cleared before you proceed.
1-5-4-3. VFO ALIGNMENT
Before starting the VFO alignment perform a VFO stability test. Connect the frequency counter to V4A pin 3.
Power up and warm up for 30 minutes. Record the VFO frequency every 10 minutes for one hour. In the one
hour test it should meet the requirements of paragraph 1-5-4 above. After 1 hour perform a short term drift test
by recording the freq every minute for 5 minutes. The short term drift should not exceed 100 cycles. If either of
these tests does not meet specifications go to the VFO DRIFT subsection of section 4. SUBSYSTEM
TROUBLESHOOTING AND TESTING for corrective action.

REPAIR AND RESTORATION OF THE SR-400
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VFO ALIGNMENT CONTINUED:
Proceed to section 8-8-A of the original manual and perform the mechanical indexing adjustments before you
proceed.
When the mechanical indexing adjustments have been completed connect the frequency counter to V4A pin 3.
Record the VFO frequency every 100 KHz from 0 to 500 (black scale). A data sheet is provided in the DATA
SHEET section with the data points and the spec frequencies. You may want to make several copies of the data
sheet.
If the actual frequency consistently falls above or below the spec frequency adjustment of trimmer C122 is
indicated. Move the dial to the black 500 index mark (be sure you are looking head on at the dial to eliminate
parallax error). Adjust C122 for exactly 4.35 MHZ.
Rerun and record the 6 data points again. If at the Ø or the 500 index mark you are more than 1 KHz off,
tracking of C122 and L21 is required. The original manual spec at this point is 2 KHZ. But it is normally not
difficult to get it less than 500 Hz. So why not try. Adjust the tuning dial to the black 500 and adjust L21 for
4.350 MHz. Adjust the dial to the black Ø and adjust C122 for 4.850 MHZ. You may have to repeat this several
times to get it correct. Under correcting or overcorrecting at one end or the other is sometimes required to get it
to fall in.
Rerun and record the data. If any of the mid points fall more than 2 KHz from spec knifing of C32A is indicated
(I use 1 KHz for my shop spec). Knifing should never be attempted on the SR-400 unless you are very
skilled at knifing. C120 is fragile and can be destroyed very easily. If you have a uniform distribution of the
error you can split the difference by adjusting C122. That is move the end points half the max error in the
opposite direction of the error.
This completes the oscillator test and adjustment process. Again let me stress that diligence in getting the
oscillators correct will pay max benefits in the end product.

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2. RECEIVER FAULT ISOLATION
YOU MUST HAVE ALL THE OSCILLATORS TESTED AND ALIGNED BEFORE PROCEEDING. SEE
SECTION 1-5.
2-1. EQUIPMENT REQUIRED.
HF RF signal generator capable of 0.5 microvolts to 300 millivolts and covering 1600 KHZ to 30 MHZ
Audio output meter (similar to General Radio 1840A).
Scope 100 MHZ or better with 1:1 and 10:1 probes or switchable probe.
Audio oscillator with 600 ohm output Z
0
capable of from 0.4 millivolts to 30v peak to peak output.
2-2. STANDARD TEST CONDITIONS
For the RECEIVER FAULT ISOLATION tests the following preset conditions are required.
OPERATION REC
FUNCTION LSB
CAL OFF
CAL ADJ MID RANGE
MAIN TUNING 250 (BLACK SCALE)
CW OFF
NOTCH CCW
BAND SELECTOR 7.0
PRESELECTOR 40
AF GAIN MAX
RF GAIN MAX
NOISE BLANKER OFF
METER RFO/S
RF LEVEL CCW
MIC GAIN CCW
RIT OFF
RIT CONTROL MID RANGE
LOAD & PLATE N/A
2-3. PROCEDURE OVERVIEW & PRESET CONDITIONS
This test is a standard progression from output to input of a receiver. It assumes the probability of multiple
faults. At any point in the procedure if a fault is detected it must be cleared before you can go the next step. The
signal levels were derived from years of testing. The levels are not absolute in that an individual receiver may
vary as much as 10%. Any deviation of more than that should be considered a fault. AGC problems can be
difficult to localize particularly if there are other faults in the system. So for the 13 step FAULT ISOLATION
procedure that follows we will disable the agc. Locate the junction of R42 and R123. Place a clip lead from that
junction to ground. Once the fault isolation is complete and the receiver is working properly tests of the agc
circuit will be performed. A 10:1 scope probe will be used to inject signals. Some measurements will
require a 1:1 scope probe and these measurements will be noted. The signal levels on the chart are injected
signal levels therefore, when using the 10:1 probe the source will be set for 10 times the level stated in the
chart. The first two audio signals are measured peak to peak using a tee connector on the audio oscillator. One
side of the tee connects directly to the scope the other to the 1:1 injection probe. The remaining signals are RMS
values as set on the RF signal generator output meter. NOTE: Section 4 contains individual ckt and sub-ckt
fault isolation tests.

REPAIR AND RESTORATION OF THE SR-400
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2-4. RECEIVER FAULT ISOLATION CHART
Injection point Frequency Signal
injection
level
Audio
output
If good go to next step. If not check suggestions below.
1
V15 pin 7 1000 Hz 14 vpp
1:1 probe
½ wt. Problem most likely V15 or associated circuitry.
See section 4-2 for details.
2
V9B pin 2 1000 Hz 0.6 vpp
1:1 probe
½ wt. Problem is most likely V9B or associated circuitry.
See section 4-3 for details.
3
V9A Pin 7 1650 KHz 5000 uv ½ wt. Problem is most likely V9A or associated circuitry.
See section 4-4 for details.
4
*
V7A Pin 2 1650 KHz 425 uv ½ wt. Problem is most likely V7A or associated circuitry.
See section 4-5 for details.
5
Tie point
C54/C59
1650 KHz 5000 uv
1:1 probe
½ wt. Problem is most likely xtal filter or notch filter.
See section 4-6 for details.
6
V6 pin 1 1650 KHz 35 uv ½ wt. Problem is most likely V6 or associated circuitry.
See section 4-7 for details.
7
V4A Pin 2 6.250
MHz
100 uv ½ wt. Problem is most likely V4A or associated circuitry.
See section 4-8 for details.
8
@
V3A Pin 2 6.250
MHz
15 uv ½ wt. Problem is most likely V3 A or B or associated
circuitry. See section 4-9 for details.
9
#
V2A Pin 9 7.250
MHz
8 uv ½ wt. Problem is most likely V2A or associated circuitry.
See section 4-10 for details.
10
~
Junction
C15&C20
7.250
MHz
6 uv ½ wt. Problem is most likely 6.5 MHz traps, S1F, V18 grid or
associated circuitry.
11
V1 pin 1 7.250
MHz
0.5 uv ½ wt. Problem is most likely V1 or associated circuitry.
See section 4-11 for details.
12
$
Tie point S1D
wiper and 6.25
trap
7.250
MHz
0.5 uv ½ wt. Problem is most likely S1D, S1C, or associated
circuitry.
13
**
J1 direct from
sig. generator
7.250
MHz
0.5 uv ½ wt. Problem is most likely K1, 6.25 MHz trap, L17 or
associated circuitry. Upon successful completion to
this point leave all equipment set as they are for
AGC test in next section.
* May require peaking of T3 @ May require peaking of T2
# may require peaking of T1 ~ May require peaking of L10 and PRESELECTOR
$ May require peaking of L3 and PRESELECTOR
** If the RX is working at this point perform
the 6meg trap alignment. See section 8-12.

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2-5 AGC TEST
The following agc test results are dependent upon overall gain and sensitivity of the receiver. This assumes a
fully functional receiver and proper alignment. If you are in the process of restoring to operation you may not
get the agc figure of merit in spec. When you have removed all the receiver and transmitter faults and have done
a completer alignment you will re-run these two tests for compliance to spec.
2-5-1. AGC FIGURE OF MERIT
With the ground jumper still connected to the agc line, tune the receiver to 7.250 MHz. Set the input at the
antenna jack to 5.0 uv. Adjust the AF gain control for 1 watt audio output.
Test 1: Remove the clip lead from the agc line. The audio output should drop about 1 db. You are now through
with the clip lead.
Test 2: Re-adjust the AF gain for 1 watt audio output with 5 uv RF input. Increase the signal from 5 uv to 5000
uv. There should be a change of less than 10 db in the audio output.
If either of these tests fails you have a problem in the agc circuit or the AGC threshold is improperly adjusted.
2-5-2. AGC THRESHOLD ADJUSTMENT
Tune up the receiver to 7.250 MHz with a 1uv signal in. Turn the AGC threshold pot fully clockwise. Set the
scope input to DC, 1v per division. Connect the scope, in DC mode, using a 1:1 probe to the junction of R2 and
C12 (in the grid ckt of V1). Slowly turn the AGC THRESHOLD pot counter-clockwise until the trace on the
scope just starts to move in the negative direction. If the adjustment is successful re-run the tests in 2-5-1 if it
fails either test there is a fault in the agc amp. NOTE: The procedure in the manual, 8-4-D should not be used.
The manual procedure sets the AGC threshold at the level of ambient noise which is always changing. By
setting the threshold at 1 uv you accomplish two tasks. First, you provide wide open gain for weak signals.
Second, you set the agc linearity start point at a measurable level insuring an accurate AGC figure of merit
measurement.
2-6. S-METER ZERO
Turn the RF GAIN and the AF GAIN controls fully counter-clockwise. Set the meter switch to RFO S. Locate
CR17. Place a clip lead from ground to the anode of CR17. Power up and warm up at least 15 minutes. Adjust
METER ZERO (R120) for a meter reading of exactly zero. If it will not zero you have a fault in the meter
circuit V8B. Remove the clip lead, if the meter moves off of zero you most likely have an agc fault in V8A, or
associated circuitry.
2-7. CAL OSCILLATOR
2-7-1. CYCLONE II TEST
Connect a frequency counter to the junction of CR10 and C88. Pull on the calibrator. Adjust C89 until it reads
exactly 100.00000 KHz. Move the probe from the counter to the scope and you should have 25vpp or better. If
it will not adjust or does not oscillate the fault is in V11B or associated circuitry.
2-7-2. CYCLONE III TEST
A . Connect a frequency counter and the collector of Q1. Pull on the calibrator Adjust C89 until it reads exactly
100.00000 KHz
B . Connect the frequency counter to the junction of L29 and C250. The counter should display 25.000 KHz. If
test A is not there or you cannot pull it in spec then V11B or associated circuitry is at fault. If test A is good and
test B is not then Q1, IC1 or the low voltage rectifier circuit is at fault. This concludes the receiver tests. About
80% of the radio is now proven to be functional.

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3. TRANSMITTER TESTING
At the start of the receiver testing you replaced the power supply fuse with a 4 amp normal delay. It is time to
re-insert the 5 amp slo-blow fuse. The goal of this section is not to get maximum power out of the radio. The
goal is simply to prove that the major transmitter sections are functioning. For now 100 watts or better is good.
CAUTION: FATAL VOLTAGES ARE OPEN AND EXPOSED ONCE THE COVERS OR CASE IS
REMOVED. OBSERVE THE FREE HAND RULE. THAT IS, ANY TIME THE POWER IS APPLIED, IF
YOU ARE RIGHT HANDED YOUR LEFT HAND IS IN YOUR HIP POCKET. IF YOU ARE LEFT
HANDED YOUR RIGHT HAND IS IN YOUR HIP POCKET
MAJOR KEY POINT, the transmitter testing process assumes that the receiver has been tested and is
operating to specs.
3-1. TEST EQUIPMENT REQUIRED
500 watt wattmeter & dummy load
100 MHz scope
Frequency counter
Audio oscillator with 600 ohm output
Driver capacitive pickup (home brew item see figure section )
600 ohm dynamic mic
Multimeter 2 VDC full-scale and 10 VDC full-scale recommended
Optional telegraph key
3-2. STANDARD TEST CONDITIONS
You will start with the following control settings
OPERATION MOX
FUNCTION LSB
CAL OFF
CAL ADJ MID RANGE
MAIN TUNING 7.3MHZ
CW filter OFF
NOTCH CCW
BAND SELECTOR 7.0
PRESELECTOR 40
AF GAIN MIN
RF GAIN MIN
NOISE BLANKER OFF
METER RFO/S
RF LEVEL CCW
MIC GAIN CCW
RIT OFF
RIT CONTROL MID RANGE
LOAD & PLATE PRESET TO VALUES ON CHART ON PAGE 20 OR 21 OF MANUAL
Wattmeter and load connected to J1.

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3-3. BIAS ADJUST (plate idle current adjustment)
With the power off plug your meter into the test jacks on the power supply chassis + to the red jack – to the blue
jack. CAUTION the meter leads will be attached to the PA high voltage, fatal shock hazard is present.
Insure the front panel settings are in accordance with paragraph 3-2 then power up. Allow 15 minutes for tubes
to get to full operating temperature. Install microphone. Key mic and adjust the BIAS ADJ on the front panel
for a reading of 0.7 volts dc on the meter. This equates to an idle current of 70 mills of plate current. Always
use this method to test and adjust the plate idle current. The front panel plate current readings are not accurate
enough to properly set the idle current.
The next series of tests will be conducted in the MOX, CW mode. You will need to switch the FUNCTION
switch from LSB to CW quite often. You MUST keep the transmit duty cycle short. I find it easier to plug a key
into the key jack on the rear of the transceiver. Then you can set the FUNCTION switch to the CW position and
leave it there and press the key when you want power. This saves wear and tear on the FUNCTION switch and
reduces the chances of leaving the transmitter keyed to long. For the remainder of the tests when you are
instructed to “key the transmitter” you will either switch the FUNCTION switch from LSB to CW or press the
key.
3-4 INITIAL TRANSMITTER TESTS
Reset all controls as stated in section 3-2
3-4-1 TRANSMITTER POWER TEST
The following tests are preliminary test to assess the overall transmitter performance. One hundred watts is
sufficient at this point.
Set the meter that is plugged into the power supply to the 10 vdc full scale range. Set the RF LEVEL to 5. In the
next series of tests monitor the plate current via the meter plugged into the power supply. One volt equals 100
mills of plate current. Keep adjusting the RF LEVEL to keep the plate current below 200 mills. Keep the
duty cycle short. Power up and allow 5 minutes warm up. Key the transmitter in the CW mode. Peak the plate
current with the PRESELECTOR. Peak the plate current with L10, L33 and LOAD. Tune the PLATE for a dip
in plate current which should coincide with a peak in power output. If the plate current dip and the power output
peak do not coincide it indicates the PA needs neutralization. You will address this later. But for now remember
to keep the duty cycle very short until you get it neutralized.
Set the band switch to 3.5, key the transmitter and adjust the PRESELECTOR, L11, L34 and LOAD for max
plate current, and dip the PLATE. Temporarily advance the RF LEVEL and record the max power out.
Set the band switch to 14, key the transmitter and adjust the PRESELECTOR, L9, L32 and LOAD for max
plate current, and dip the PLATE. Temporarily advance the RF LEVEL and record the max power out.
Set the band switch to 21, key the transmitter and adjust the PRESELECTOR, L8, L31 and LOAD for max
plate current, and dip the PLATE. Temporarily advance the RF LEVEL and record the max power out.
Set the band switch to 28.5, key the transmitter and adjust the PRESELECTOR, L7, L30 and LOAD for max
plate current, and dip the PLATE. Temporarily advance the RF LEVEL and record the max power out.
If you achieved 100 watts on all bands (50 watts on10 meters) proceed to section 4-2 PA NEUTRALIZATION.
When the neutralization is complete it is time to move on to a complete alignment. Some of the alignment has
already been completed. You will need to complete the following steps in the manual: 8-5 and 8-9 through 8-12.
If the minimum power is not achieved proceed to section 3-5 the TRANSMITTER FAULT ISOLATION. Once
you get the transmitter working then return to the beginning of 3-4-1 and proceed from there.

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3-5, TRANSMITTER FAULT ISOLATION
The assumption at this point is that the receiver works. If it does not you need to back up to section 2 and clear
the receiver faults. For the fault isolation tests preset the equipment as listed in 3-2. STANDARD TEST
CONDITIONS.
3-5-1, DRIVER CAPACITIVE PICKUP TOOL
The driver capacitive pickup tool is simply a metal sleeve. It is constructed to be a close fit over the driver tube
in place of the normal tube shield and NOT making contact with ground. As shown above I took an old tube
shield, removed the internal spring and cut off the base of the shield. I then bent a large loop one end of a piece
of buss wire, just a little larger than the inside diameter of the shield. On the other end of the buss wire I formed
a small loop. Using the tabs that originally held the spring in place in the shield, I mounted the buss wire
assembly in the shield
**The amplitude of the sampling depends upon how you construct your pickup. The length of the tube and the
closeness of the fit will affect the coupling. The one pictured above shows 40 vpp for 200 watts output at 3.900
MHz. You will need to test your device on a working system to develop the norms for it.

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3-5-2, LOW OR NO POWER ACROSS ALL BANDS
A. Set the band switch to 3.5 and the main tuning to 3.9MHZ. Set the PRESELECTOR near the upper end of
the 80 meter band. Power up and warm up. Remove the shield from V18 and install the DRIVER
CAPACITIVE PICK UP tool. Connect the scope to the pick-up tool. Key the transmitter, peek the
PRESELECTOR, L11 and L34. If you have **40 vpp on the scope, unkey the transmitter. Move the probe from
the scope to the frequency counter, key the transmitter. You should get 3.9MHZ on the counter. Unkey the
transmitter. If you have 3.9MHZ at **40 vpp or better and there is no or low power out, your problem is in the
PA. If not go to step B.
B. Connect the 10:1 scope probe to pin 2 of V18. NOTE: as soon as you connect the probe to the tie-point you
will detune the ckt. Some adjustment of L11 may be required to peak the signal. Key the transmitter advance
the RF LEVEL control to 7 and peak L11. A signal level of 5 vpp should produce 200 watts. If you have 5 vpp
and still no power out the problem is in the driver or associated circuitry. If the signal is incorrect go to step C.
C. If the signal is not correct connect the probe to pin 7 of V11. Pull V2. Key the transmitter; you should see 4
vpp on the scope. If the signal is correct go to step D. If it is not, and since the receiver is working properly, the
problem is in the Het Osc transmitter switching circuit. Check the dc voltage on the tie point of L20 and the
cathode of CR11. It should be greater than 14 volts in receive mode and less than 1.9 volts in transmit mode. If
this voltage is correct then either CR11 or C47 is bad. The voltage on the cathode of CR11 is developed by the
cathode current of V15 (the audio output tube). If the voltage on the cathode of CR11 does not drop in transmit
mode check the grid of V15. The grid should go to gnd in transmit mode, if it does not check relay K2. If the
voltage is not correct in receive mode measure the voltage on the opposite end of L20. If the voltage is good
then L20 is bad.
D. Reinstall V2 and remove V12. Connect the scope to pin 7 of V11. Key the transmitter. You should have 3.5
vpp. If the signal is correct, and the test B above was good, then the fault is in V11 and its associated circuitry.
E. If the signal is not good, reinstall V12 and move the scope to pin 7 of V2 (VFO signal injection). Key the
transmitter and you should have 3.5vpp. If the signal is not correct the fault is most likely CR34 or V2.
F. If the signal is good move the scope to V2 pin 2(carrier/balanced mod injection signal). Key the transmitter.
If the signal is 0.6 vpp the fault is most likely in V2, or its associated circuitry. Note: Here again since you have
proven that the receiver is functioning properly you can eliminate T1, T2 and V3 as a cause.
G. If the signal is not good move the probe to V6 pin 1. Key the transmitter. The signal should be 1 vpp. If the
signal is good then the fault is most likely the alignment of L15 and L16. If the signal is not good the fault is in
the balanced modulator T6 and its associated circuitry.
This completes the transmitter fault isolation process. You should have found the fault at this point. If not then
verify that the receiver is functioning properly. Then restart section 3 test procedures. There are many circuits
that are used in both RX and TX, by verifying the RX functions you are also proofing all the common ckts.
3-5-3, NO OR LOW POWER ON A SINGLE BAND.
Select the affected band and follow the procedure in 3-5-2. Eliminate the common components and concentrate
only on the switches and switched components. Go back and review the results of tests in 1-5-3 (het osc tests).

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4. SUBSYSTEM TROUBLESHOOTING AND TESTING
4-1 VFO DRIFT
You have performed all the tests in section 1-5-4 and determined that you have a drift problem. Perform the
drift test in receive, LSB mode. Then perform the same test in receive, USB mode. If you have the drift problem
in USB but not LSB the most likely cause is CR12, C126 or C127. A bad ground on C127 could also be a
source of trouble. If you determine the drift is the same in LSB and USB just about any of the N or NPO
capacitors inside the VFO enclosure could be suspect. Grounding particularly on C120 and C122 could also be
the source. You can either shotgun the VFO and replace all the caps or replace them one at a time until you find
the bad one. In many cases more than one is contributing to the failure.
4-2. V15 RX FAULT ISOLATION
Turn the power 0ff. Disconnect the power supply. Pull V15. Inject 1000 Hz at 20 vpp into pin 5 of the V15
socket. Connect J5 (AUDIO 500 ohm phono jack on rear of chassis) to the scope. If you get 15 vpp at J5 the
output transformer and associated circuitry are good. If it failed step 1 in the RECEIVER FAULT ISOLATION
CHART then V15 or its associated circuitry is at fault.
4-3. V9B RX FAULT ISOLATION
This circuit is pretty straight forward. Check the voltages and resistances against the charts in the manual. If
they are correct then the options are few. C78, C77 or R48 are the most likely cause of the fault.
4-4. V9A RX FAULT ISOLATION
Power up and set the standard test conditions. In LSB mode you should have a 6 vpp signal on pin 8 of V9A.
Move the probe from the scope to the frequency counter. You should see 1650 KHz on the counter. If you do
not get the proper level of signal on frequency then the fault is likely in the BFO/Carrier oscillator or C138.
4-5. V7A RX FAULT ISOLATION
Perform the voltage and resistance test per the charts in the manual for V7. If the voltages and resistances are
good then the likely cause of the fault is; V7A, C8, C60, C71, C72 or T3.
4-6. XTAL RX FILTER/NOTCH FAULT ISOLATION
Lift the lead of C61 that connects to Y12. Into the lifted lead of C61 inject 1500 uv of 1650 KHz you should get
½ watt of audio out. If you get ½ watt of audio then the fault is in the Y12/CR23 bias or switching networks.
Reconnect C61. If you do not get the ½ watt audio move the injection probe to the output side of the filter.
Reduce the level of injection to 500 uv. If you get ½ watt audio output then the filter is bad. If you do not get
proper audio out then L16, R169, C228 or Y13 and its associated bias and switching network are at fault.
4-7. V6 RX FAULT ISOLATION
NOTE: In this next step you will be injecting signal into the plate pin of the tube socket. If your probe is
NOT D.C. blocking and not rated for 300 vdc or higher you WILL DESTROY the attenuator in your
signal generator. You will need to acquire or construct an injection probe that will handle that voltage.
Pull V6, power up and inject 3000 uv at 1650 KHz into pin 5 of the V6 socket. If you do not get at least ½ watt
audio out then L5, C54, C59 or C182 is at fault. If you get ½ watt then V6 or associated circuitry are at fault. If
the tube is known to be good then refer to the voltage and resistance charts in the manual. If the voltages and
resistances are correct then suspect C55, C56, C57 or C245. If all this checks ok then pull V5 and repeat step 6
in the RX FAULT ISOLATION chart (Paragraph 2-4). If you get ½ watt audio out then V5 or its associated
circuitry are at fault.

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SUBSYSTEM TROUBLESHOOTING AND TESTING
4-8. V4A RX FAULT ISOLATION
Assumption: You have injected 35uv @ 6 – 6.5 MHz into pin 1 of V6 and there was ½ watt audio output. And,
when you inject 100uv into pin 2 of V4 you do not get ½ watt output. Check for 260 Vdc pin 1 of V4. If there is
no 260 Vdc check pin 1 and 2 of T6. The B+ is supplied to V4 through R126 and T6. Pin 2 of V4A should be
zero volts dc in receive mode. If it is a high negative voltage, clean the contacts (pins 9, 1 and 5) of relay K2.
Pin 3 of V4 should have 1.5 vpp RF injection from the VFO and the DC bias should be approximately 11vdc. If
the DC bias is incorrect then either R30 or the tube is bad. If there is no injection RF on pin 3:
CYCLONE II suspect C53
CYCLONE III suspect CR30, R176 or C223.
4-9. V3 RX FAULT ISOLATION
WARNING DAMAGE TO TEST EQUIPMENT POSSIBLE. See note in 4-7. Pull V3 and check the
voltage on the socket pin 6, it should be 260 vdc. If there is no 260 vdc then suspect T2, C42 or R23. With V3
pulled inject 6.25 MHz at 150uv into V3 socket pin 6. Tune the main tuning to approximately 250 on the black
scale, and peek the audio output. If you do not get ½ watt audio out then suspect C42, C44 or T2. If the
proceeding checks are good there is a bias problem or V3 is bad. If V3 is known to be good refer to the voltage
and resistance charts in the manual to isolate the fault.
4-10 V2 RX MIXER FAULT ISOLATION
WARNING DAMAGE TO TEST EQUIPMENT POSSIBLE. See note in 4-7. Pull V2 and check the
voltage on the socket pin 6, it should be 260 vdc. If there is no 260 vdc then suspect T1, C30 or R16. With V2
pulled inject 6.25 MHz at 25uv into V2 socket pin 6. Tune the main tuning to approximately 250 on the black
scale, and peek the audio output. If you do not get ½ watt audio out then suspect C30, C31 or T1. If the
proceeding checks are good there is a bias problem, injection problem or V2 is bad. If V2 is known to be good
refer to the voltage and resistance charts in the manual to isolate the fault. If the tube voltages and resistances
are good check the mixer injection voltage. Pin 7 of V2 should have 1.5 vpp at approximately 4.600 MHz.
4-11 V1 RX FAULT ISOLATION
WARNING DAMAGE TO TEST EQUIPMENT POSSIBLE. See note in 4-7. Pull V1 and check the
voltage on the socket pin 5, it should be 260 vdc. If there is no 260 vdc then suspect L6. With V2 pulled inject
7.25 MHz at 45uv into V1 socket pin 5. Tune the main tuning to approximately 250 on the black scale, and peek
the audio output. If there is no audio output then C15 is open. If there is audio output but you cannot get ½ watt
ground the tie point of R3, R5 and R7. If the audio increases more than 2db then the RF GAIN pot is at fault.
Check the voltages and resistances per the charts in the manual.

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5. TECH NOTES
5-1. BASIC TUNE UP
The RF power out and PLATE current monitoring leaves a little to be desired in the SR-150 through the SR-
500. This short fall was corrected in the SR-2000 with the addition of a dedicated plate current meter in the
power supply.
5-1-1. THE PROBLEM:
During PA tune up the RF power out peak and the plate current dip (true resonance point) do not always
coincide. Proper tuning should always be to the plate current dip. To accomplish this the way the equipment is
designed requires constantly switching the meter switch on the 400 from RFO to PLATE MA. Proper
neutralization of the PA finals will minimize this effect. Regardless of how well the equipment is neutralized
differences in the power peak and the plate current dip will occur across the bands.
5-1-2. WHY IS THIS IMPORTANT?
At true resonance the PA tubes are operating at their most efficient point, and this adds to the life of the tubes.
At true resonance spurs and harmonics are at minimum.
At true resonance components in the plate circuit are under minimum stress (very important in the SR-150).
At true resonance you rig just sounds better.
5-1-3. A SIMPLE SOLUTION.
Plug an external meter into the test jacks in the power supply and leave it there as a permanent monitor.
Commonly one of the jacks is red the other is blue. CAUTION the meter leads will have the plate voltage
present at all times. The meter should be set to the 10vdc full scale range, red lead to the red jack and black lead
to the blue jack. Then you can leave the meter switch in the RFO S position during tune up and operation. The
only time you will need to change the meter switch is when checking AALC.
5-1-4. SUMMATION:
This simple meter addition not only simplifies tune up but adds a constant critical monitor to your system. Any
problem in the PA, transmission lines or the antenna are immediately reflected in the plate current.

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5-1-5. MANUAL SECTION 5-4 MARK UP:
The following is a markup of section 5-4 in the original manual.
The “red etters” are suggested deviations and cautions from original manual section 5-4.
5-4 BASIC TRANSMITTER TUNE-UP
The Model SR-400 Transceiver can be tuned up
on several frequency segments that are outside the
amateur bands. Care must be exercised not to transmit
on these frequencies. The receiver group of controls, not
specifically mentioned below, has no direct bearing on
the transmitter tune-up procedure and may be
disregarded for the moment.
A. Pre-set the panel controls for transmitter tune-up as
follows:
OPERATION…………………………………….REC
FUNCTION…………………………………….TUNE
BAND SELECTOR……………………..Desired band
PRESELECTOR…………..Set at band segment in use
Tuning dial………………...…Set to desired frequency
METER…..………….………….………...PLATE MA
The meter circuit common y has an accuracy of +
or – 20%. It is high y recommended that the initia
bias adjustment be done with an externa meter
connected to the p ate current jacks, TP201 and
TP202 on the PS-500. For operationa tune up
procedures the meter ckt inaccuracy is not an
issue. It is of great benefit if the p ate current and
the power out are monitored simu taneous y. If
you norma y operate your station with an in ine
wattmeter, set the meter switch to PLATE-MA. If
an in ine wattmeter is not used, do the fo owing.
Attach a meter to TP201 and TP202 on the power
supp y chassis to monitor the p ate current. Set
the meter switch to RFO/S to monitor the power
out.
RF LEVEL……………………...…At zero (Full CCW)
MIC. GAIN……………….……… At zero (Full CCW)
At initia turn on and at shutdown a ways set
these two contro s to zero or fu CCW. This wi
essen the possibi ity of inadvertent emissions
that cou d damage the transceiver and shorten
the ife of the PA tubes.
* PLATE (Final tune capacitor)……Use chart settings
*LOAD (Final loading capacitor…..Use chart settings
Do not take the recommendation be ow ight y.
There are an infinite combination of settings of
the LOAD and PLATE contro s that wi provide
resonance and a p ate current dip. The settings
suggested in the chart are the design center
starting points and shou d be strict y adhered to.
The chart is found on page 20 of the origina
CYCLONE and CYCLONE II manua s and page 21
for the CYCLONE III
.
*IMPORTANT
Presetting the PLATE and LOAD controls
per the chart will avoid incorrect control
settings and minimize plate dissipation in
the final amplifier tubes during the turn-up
procedure.
B. If the transceiver has just been turned on allow a
few minutes for the equipment to reach operating
temperature before proceeding with the transmitter
tune-up.
With the METER selector switch set at PLATE MA
the meter pointer will normally rest to the left of the
meter scale zero when the transceiver is in the receive
mode. This is normal for the meter circuit used in the
transceiver.
Caution: From this point on any time you switch
from REC to MOX you wi be in TX mode if you
have proper y set the preconditions isted in
paragraph A. Be aware of the p ate current and
power out at a times. Keep the duty cyc e ow, 5
seconds TX with min 10 seconds rest in RX. Read
a of paragraph C before you start. Each of the
fo owing paragraphs shou d be read and
understood before any adjustments are made.