Ampex 1050 User manual

7890021-03
MAINTENANCE MANUAL FOR
TAPE RECORDER MODELS
1050, 1070, 10 80
2050, 2070, 2080
SPEAKER MODELS
1015, 1016
2010, 2011
AMPEX SERVICE COMPANY
2601 GREENLEAF AVENUE
ELK GROVE VILLAGE
ILLINOIS 60007
SEP 1973

SPECIFICATIONS
Specification Model
1070
1050 /1080 2070
2050 /2080
Pre-amp overall freq.
response
7-1/2 ips
50 to 15000 cps +- 4db 50 to 15000 cps +- 4db 50 to 15000 cps ±3db 50 to 15000 cps ±3db
3-3/4 ips
50 to 7500 cps +- 4db
50 to 7500
cps ±4db 50 to 9000
cps ±4db 50 to 9000 cps +- 4db
1-7/8 ips 50 to 4000 cps ± 4db 50 to 4000 cps ± 4db 50 to 5000 cps ± 4db 50 to 5000 cps ± 4db
Signal to Noise from peak
record level at pre-amp
7-1/2 ips 46db 47db 49db 50d db
3-3/4 ips 42db 43db 45db 46db
1-7 / 8 ips 38db 39db 40db 41db
Tone Control Range
100 cps
0 to +12db N/ A 0
to +12db N/ A
10KC
-4 to +10db N/ A
-4 to +10db N/ A
Power Output (rms) 3 watts
N/ A 6
watts
N/A
each channel
Flutter
7-1/2 ips
0.15% 0. 15% 0.12% 0.12%
3-3/4 ips
0. 2% 0. 2%
0.15%
0.15%
1-7/8 ips 0. 3% 0. 3% 0. 25% 0. 25%
Timing Accuracy
7-1/2 ips ±1.5% ±1.5% ±1%
±1%
3-3/4 ips ±3% ±3% ±2%
±2%
1-7/8 ips ±4% ±4% ±3%
±3%
Fast Wind Time
(1200 feet of tape) 130 seconds 130 seconds
130 seconds
130 seconds
Line Input Impedance 120K 120K 120K 120K
Microphone Input
Impedance
1 megohm
1 megohm 1 megohm
1 megohm
Line Input Level
. 2V min
.2V min
.2V min
. 2V min
2. OV max
2. OV max 2.0V max 2. OV max
Microphone Input Level 3mv min
3mv min 3mv min
3mv min
30mv max
30mv max
30mv max
30mv max
P.re-Amp Output Impedance 1000 ohms
1000 ohms 1000 ohms
1000 ohms
Pre-Amp Output Level
,3 v min
1 v .3 v
min
V
Power Amp Output
8 ohms N/ A 8
ohms
N/A
Impedance
OVERALL SIZE
19" X 13-1/2" X 7-1 / 2 N/ A
19" X 13-1 / 2" X 7-1 / 2"
N/ A
Mounting
Frame
N/ A
18-5 / 8" X 13" X 5-1 / 8"
N/ A
18-5 / 8" X 13" X 5-1/8"
Weight
37 lb
27 lb
39 lb
29 lb
Power
Requirements
117vac at 1 ampere
117vac at . 9 ampere
117vac at 1 ampere
117vac at 1 ampere
(Volume at minimum)

-
This manual contains information relative to 1000 and 2000 series equipments.
Anyone who is attempting repair, parts replacement, or adjustment should first
READ THIS MANUAL. This will shorten trouble shooting time and expedite parts
replacement. Please note the various paragraphs relating to specific repairs such
as head replacement, torque measurements, etc.
The information in this manual is the latest available. As additional information
becomes available, it will be presented on manual change sheets and/ or service
bulletins.
This manual supercedes all previously printed manuals
of the same part number and Service Bulletins . No. 1021 CD
1028 CD, 1044 CD, 1049 C,
i

CIRCUIT DESCRIPTION . . . . . . . . .
Playback (Left Channel 2070 only) ...
Reverse Relay (Applying 20 cps Signal)
Reverse Signal (Received from Tape)
REPEAT MODE OPERATION ....
AUTO PLAY MODE OPERATION .
MONITOR CIRCUIT . . . . . . . . .
CHANNEL 2 (RIGHT)
OPERATION .
POWER SUPPLY . . . . . . . . . .
BIAS OSCILLATOR
........ .
REMOVAL
OF RECORDER FROM CASE
CASE REMOVAL . . . . . . . . . . . .
CAPSTAN DRIVE BELT REPLACEMENT
TORQUE MEASUREMENTS . . ..... .
TABLE OF CONTENTS
..
EQUIPMENT REQUIRED FOR MECHANICAL CHECKOUT & ADJUSTMENT
MECHANICAL CHECKOUT & ADJUSTMENT .
. . . . . . . . . . . . . . . .
LUBRICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MECHANICAL
TROUBLES & PROBABLE SOLUTIONS . . • . . . . . . . . ...
PRELIMINARY REQUIREMENTS FOR ELECTRICAL CHECKS & ADJUSTMENT.
PRELIMINARY CHECKOUT INSTRUCTIONS
NOISE
FILTER ...........................
100/1 CAPACITIVE DIVIDER PROBE .............
HEAD REPLACEMENT & ALIGNMENT . . . . . . . . . . . .
1050/1080/2050/2080 ELECTRICAL CHECKS & ADJUSTMENTS
1070/2070 ELECTRICAL CHECKS & ADJUSTMENTS .
ELECTRICAL TROUBLES & PROBABLE SOLUTIONS
ORDERING
PARTS & USING THE PARTS LISTS
ASSEMBLY
PART NUMBERS ..... .
PARTS WITHIN ASSEMBLIES ......
MISCELLANEOUS ELECTRICAL PARTS
1015 SPEAKER SYSTEM PARTS LIST
1016 SPEAKER SYSTEM PARTS LIST .
2010
SPEAKER SYSTEM PARTS LIST .
PAGE
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2011 SPEAKER SYSTEM PARTS LIST .
DC
TUBE & TRANSISTOR VOLT AGES .
SCHEMATICS
..........
. • . . . . . • • . . . . • . . . . . . . . . . . . . . • . . . . . . 38
• • . • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 39-48
ii

CIRCUIT DESCRIPTION
I Playback (Left Channel 2070 only)
During playback, signals from the tape cause a voltage
to be induced in the playback head. Since this is a
very low voltage, .5mv or less, amplification is
required. Tube Vlab amplifies the low level voltage
and applies it to volume control R23a. Resistor R23a
controls the amount of signal applied to V2a. Output
of V2a
is applied through S6a and S5d to the tone
control circuitry and thus to V2b. Output of V2b is
used to drive NPN transistor Ql. Output of Ql is
transformer coupled to power transistors Q2 and
Q3. Both
power transistors have a small forward
bias to eliminate turn-on distortion. When Q2 is
conducting because of ac signal, Q3 is turning off
due
to lack of ac signal, and vice-versa. Capaeitor
C30 then alternately charges through speaker LSl
and Q2 to B- and discharges through LSl and through
Q3 and ground.
ll Reverse Relay (Applying 20 cps Signal)
The mechanical reverse relay appears electrically
as a very high Q parallel resonant circuit, thus
requires a very small amount of signal power for
operation and has a very narrow pass band. When
the reverse signal is applied, the following occurs:
The armature of the relay oscillates because of
mechanical coupling from REV SIG knob. Since the
coil of the vibrator has a de bias applied, there is
an ac voltage developed as a result of the mechanical
motion and changing flux path. This ac voltage
(20 cps) is applied through S5J to the grid of V6a.
Feedback from the plate of V6b applies every fre-
quency except 20 cps back to the grid. The output
at the plate, as the result of this feedback is a
very low distortion sine wave and is applied through
R142 to S5b and again S6d to S6a. Switch S5b is
applied to S6a and S5a. The 20 cps signal is then applied
to L6-Cl3, S4d, C8, and S3a to the record head Ll9
and signal is recorded on the tape. Coil L6-Cl3
and L5-C18 are traps to prevent the bias signal
from getting into the amplifier circuits. Beat fre-
quencies and overloading may result if the bias signal
gets into the amplifiers.
NOTE
For reception of 20 cps signal from tape,
see next paragraph.
Ill Reverse Signal (Received from Tape)
Assume tape is moving from left reel to right reel.
This is the condition as shown on the schematics.
When the 20 cps signal is on the tape, it induces a
voltage into
head Lla. The voltage is applied to
Vlab, output of V lb is applied to S5a, and to the grid
of V6a. Output of V6a is applied to grid of V6b.
Output of V6b
is applied through C82 and S5q to
K3 (coil). This 20 cps signal causes the armature
of K3 to oscillate (vibrate), causing closure of the
vibrator contacts. When the contacts close, Kl is
energized. This causes current flow from ground
through Ll0 and closed contacts of Klb and K2a
to 30 volt supply, causing the reverse solenoid L3
to operate. Resistor R58 provides hold-in current
when Kl contacts open. When Ll0 operates, SlOc
contacts change state and the head switch S2a switches
the heads. Relay Kl holds in for about 1/2 second
because of capacitor C83. When the capacitor dis-
charges, Kl de-energizes and relay K2 is not shorted
by Kla ·contacts and its own contact K2a. Relay K2
therefore energizes because of current flow from
ground through upper closed contacts of SlOc, through
R145, through K2 coil and to 30 volt supply. This
causes K2a contacts to change state.
When a second 20 cps signal is received, relay K3
armature vibrates causing Kl to be energized. This
causes Kla and Klb contacts to change state (for
1/2 second because of C83). Note that now contact
K2a is also closed. Solenoid L3 is shorted by closed
contacts K2a and Klb and thus de-energizes, causing
motor Bl to reverse and playback heads are switched
again by S2a. Contacts Sl0c go back to the position
shown on the schematic. Relay K2 de-energizes,
causing K2a contacts to go to position shown on
schematic. When the next 20 cps signal is received,
K2 will not energize immediately, because it will
again be shorted by contacts K2a and Kla when Kl
energizes. It will only energize after the motor
reverses.
When a plug is inserted into J8, the following occurs:
a. A 30 volt de pulse of about 1/2 second duration is
applied to a projector actuator or other device.
b. The reverse solenoid Ll0 contacts SlOa, Sl0b,
and Sl0e will not change state because when the
plug is inserted into J8, Ll0 cannot be shorted by
Klb and K2a contacts, thus recorder always moves
in the same direction unless manually reversed.
Relay K2 cannot energize because the second pair
of contacts on J8 are also open and the lower part
of K2 cannot be grounded.
REPEAT MODE OPERATION
When
the play/record knob is in Auto Play, the
recorder will reverse automatically in either direction
as described previously.
AUTO PLAY MODE OPERATION
When
the play/record knob is set to the Auto-Play
position, the recorder will play from left to right,
reverse as described previously, then will not reverse
even if another 20 cps signal is recorded in the right
to left direction. The recorder will simply disengage
itself. If the AC switch (2000 series only) has been
used as a slumber switch, the recorder will shut off
completely. The reason is as follows:
The lower contact of K2a will not be grounded by
S5s when in
the Auto- Play position. This is the
position shown on the schematics for S5. Thus when
the first 20 cps signal causes Kl to energize, the
reverse solenoid Ll0 operates reversing the motor.
Relay K2 will momentarily energize, then de-energize
1

as K2a contact does not have a ground return.
However, reverse solenoid L10 has hold-in current
supplied through R146 and remains energized. When
the second 20 cps signal causes K1 to energize,
reverse solenoid L10 will not be shorted by contacts
K1b and K2a, because K2a will not be at ground poten-
tial. Thus the 20 cps will come and pass and the
recorder will remain in motion from right reel to
left reel. When the tape is exhausted from the right
reel, the tape tension switch Sll will open and remove
power from the reverse solenoid and play solenoid.
The recorder will therefore go into neutral (no tape
motion) and the motor will return to the rotation
giving left to right tape motion. If the slumber switch
is used, when the play mechanism returns to neutral,
micro switch S9 will open removing power from
recorder completely.
MONITOR CIRCUIT
During record, it may be desirous to monitor what
is being reco rded onto the tape. In models 1070 and
2070,
switch S7ab applies a very small signal to the
inputs of the power smplifier. The speakers therefore
produce very low volume signals when the Monitor
switch is on. The models 1050, 1080, 2050, and
2080
have the same feature except that the switch is
a front pane l control (S14abc).
CHANNEL 2 (RIGHT) OPERATION
The right channel operation is almost the same as
left channel operation except that the reverse signal
is not associated with this channel.
POWER SUPPLY
The power supplies are conventional. The higher
voltage power supply uses a voltage doubler. The
lower voltage power supply is full wave.
BIAS OSCILLATOR
The bias oscillator is a tuned push-pull oscillator
operating at a frequency of approximately lOOkc.
Its output is transformer coupled to the erase heads.
Bias power for the record heads is supplied through
variable capacitors C12 and C49.
REMOVAL OF RECORDER FROM CASE
Top Plate Removal
1. To remove the top plate the plastic head cover
and the lower front trim strips must be removed.
The head cover is removed by pressing inward along
the inside surfaces and lifting off the head cover.
The lower front plastic trim strip is removed by
pushing inward slightly on the i nside edge facing the
heads and lifting off. If pl a stic reel covers and
auto-thread reels are installed , they also must be
removed.
2. Remove the four Allen screws at upper and lowe r
ends of top plate. Remove the 2 Phillips s cre ws which
were beneath the head cover and the two which were
beneath the lower front plastic trim strip.
3. The top plate will slide off towards the reels.
2
CASE REMOVAL
1. To remove the recorder from the case, remove
two Phillips screws in each side casting. These are
castings at sides which have speaker parts in them.
2. Remove the two Phillips screws at the top of case
securing the large decorative casting. These are
exposed when top plate is removed.
3. Remove the two Phillips screws at the bottom of
case securing the large decorative casting. These
are also exposed when top plate is removed.
4. Lift out recorder from the case.
5. The case is installed in reverse manner of removal.
CAPSTAN DRIVE BELT REPLACEM ENT
To replace the capstan drive belt (flywheel drive belt),
proceed as follows :
1.
Refer to the capstan drive belt illustration . Remove
the pin at the bottom of the play solenoid. This allows
the plunger and brass rod to be removed from the
solenoid.
2. Remove the four screws as shown in the illus-
tration.
3. Carefully remove the defective belt from motor
pulley and shift fork. Lift up on the capstan housing
thrust plate and belt will slide out from beneath
thrust plate. Note that the play actuator lever must
be moved to allow easy removal of belt.
4. Replace belt in reverse manner of belt removal.
Carefully install on motor pulley and in belt shift
fork.
5. Replace screws in capstan housing and plunger into
play solenoid.
6. Replace pin in play solenoid. Replacement is com-
plete and recorder is ready for use.
TORQUE MEASUREMENTS
Torque is a measured force times the distance
between the point of measurement and a pivot point.
For exa mpl e , 5 oz. in. of torque would be a force of
5
oz. at 1 inch from the pivot point. A wheel 3 inches
in diameter requiring 2-1/2 oz. of pull to move or
prevent from moving represents a torque of 3. 75 oz.
in. (1.5 x 2.5). In the
case of an arm or rod, the force
required to move or hold stationary must be at right
angles to the arms or rod. Otherwise torque measure-
ment will be erroneous. In addition, static friction and
or inertia someti m es must be overcome. Therefore,
it is adviseable when measuring torque to move the
reel very slowly in direction of reel take-up to
relie ve fr iction or i nertial effects when measuring reel
holdb a ck and tak c-up torques. Note that the torque
indications will be different when gauge is held station-
ary and when g au ge is just moving. When mea suring
holdback tension , note torque measurement after reel
has just started to rotate because of pull placed on
reel by spring gauge and pull on gauge is steady while
reel just rotates.

REMOVE SCREW
REMOVE
SCREW
REMOVE PIN BY
SPREADING
BRACKET
REMOVE
SCREW
Capstan Drive Belt Replacement
EQUIPMENT REQUIRED FOR MECHANICAL CHECKOUT AND ADJUSTMENT
The following equipment or its equivalent is required
for mechanical checkout and adjustment:
Spring gauge, 0 to 8 oz.
0 to 32 oz.
0 to 64 oz.
a. Flutter Meter, Varo Model FL3D
b. Long Nose Pliers
c. "E" Ring Pliers
d. Set of Allen Wrenches
e. Phillips Screwdrivers
f. Head Cleaner, Ampex P ' N 010823
g. Head Demagnetizer, Ampex P/N 010820
h.
Flutter Tape, Ampex P/N 31326-01 (7-1/2 1ps)
and 31336-01 (3-3/4 ips)
j. Alignment Tape, Ampex P/N 31321-04
k. Reel of blank (erased) tape of type to be used
on recorder.
l. Ammeter, AC, 0 to 3 amperes
m. Special reel - consists of two standard 3 or 4
inch hub reels which are cemented together. Enables
accurate torque measurements. Reel has string or tape
installed on top r eel, thereb y preventing tape or string
from rubbing on frame casting.
3

MECHANICAL CHECKOUT AND ADJUSTMENT
Preliminary Requirements
The following are required for all tests and adjust-
ments unless otherwise specified:
a. Line voltage at 117 V AC.
b. Pre-amp output terminated with 100,000 ohm
resistor.
c. A filter, down 3 db at 30 and 18,000 cps must be
used for all noise measurements. (See filter construc-
tion details).
d. Demagnetize the heads, capstan, and tape guides.
Check
for cleanliness also. If necessary, clean with
head cleaner.
Mechanical Checks
a. Apply power to the recorder. Measure the AC
line current with the recorder in neutral (no motion).
Line
current should be approximately one ampere.
b. Supply Reel Holdback Torque. The supply reel
holdback torque should be between 1.9 and 2. 7 ounce-
inches in both forward and reverse PLAY modes.
The supply
reel holdback torque should be between
. 7 and 1.4
ounce-inches in both forward and reverse
WIND modes.
If torque is not within the above limits, adjust-
ment can be made by moving the triangular shaped
bracket beneath the casting. (Refer to illustration.)
The screw is loosened and the bracket is moved in
the
direction necessary to give proper holdback torque.
Then the screw is tightened. The adjustment is the
same for both reels.
4
NOTE
The supply reel will become the take-up reel
and vice-versa, depending upon tape motion.
c. Take- Up Torque. The take-up reel should have a
torque of between 1. 9 and 2. 7 ounce-inches when in
forward and reverse PLAY modes
If torque is not within this limit, adjustment can
be made by
turning the screw which changes spring
tension on the white hold-back pulley. This is the
white pulley having the
small black tire which engages
with the large white turntable pulley.
d. Capstan
Idler Pressure. In the PLAY mode, a
force of 2.3 to 2. 65 pounds applied at right angles to
the capstan idler arm at the capstan idler shaft should
just lift the idler clear of the capstan.
If the force required to just disengage the capstan
idler is not within the above limit, adjustment can
be made by turning the screw at the lower right of
the left hand
idler or at the lower left of the right
hand idler, (Refer to illustration.)
e. Speed. The average speed with a tape pack radius
of 2 to 2-1/2 inches on each reel should be as follows:
7-1/2 ips - plus or minus 1%
3-3/4 ips - plus or minus 2%
1-7/8 ips -plus or minus 3%
f. Fast Wind Time. The time required to transfer
1200 feet of 1-1/2 miltapefromsupplyreel to take-up
reel should be 120 seconds or less.
g. Flutter. Flutter should be measured using Ampex
Flutter Tape, part number 31326-01. Flutter at 7-1/2
ips should be 0.12% or less, 3-3/4 ips, 0.15% or
less, and at 1-7/8 ips, 0.25% or less. These specifi-
cations are for tape movement in either direction.

LUBRICATION
MOTOR LUBRICATION
The
motor bearings should have several drops of
Ampex Oil
P/N 01-0825 after each 1000 hours oper-
ation. A small oil port is located on each bearing
casting. Do not allow oil to run out between bearing
and motor shaft as this is an indication of excessive
oil. This oil is similar to OC-11 lubricant.
TRANSPORT MECHANISM LUBRICATION
Lubrication of the tape mechanism can be performed
by using the following recommendations:
1. Use Ampex P/N 087-060 (grease · similar to Shell
BRP#1) on
all moving but not rotating parts such as
yoke bearings, etc.
2. Use Ampex P/N 087-516 (fluid, d.c. 266,000
centistokes), on the tape tension switch (beneath cast-
ing) ONLY.
3. Use Ampex
P/N 087-527 grease to deaden ringing
sounds where necessary. It should never be used on
fast moving or rotating parts.
4. Use Ampex P/N 01-0825 on all rotating or fast
moving parts. This is the same type oil as is used to
lubricate the motor.
5

PROBL EM
Tape s ticks in tap e guide
Poor sp eed chan ge action
Poor s lack tak e- up
6
LOOSEN TO
AOJ BRAKES
TAKE-UP
AOJ
TAKE-UP
AOJ
Kl SIOabc
REV. SOLENOID
SWITCH
ADJ
Adjustments (beneath deck)
LOOSEN TO
AOJ BRA KES
MECHANICAL TROUBLES AND PROBABLE SO LUTIONS
POSSIBLE SOLUTION
5
Check brass tape guides. The clearance between tap e gui de over
capstan idler arms shall be approximately .005. It is a MUST th at
the tape guide shall not, at any place, touch either the i dler arm or
the capstan roller. If necessary, adjust tape guide as required , by
cautiously bending tape guide over idler arm. Check ta pe for proper
width.
Position speed selector knob at 3-3 / 4 ips (center positi on) and pull
compensating rod into selector knob nest; rod shall e nter freely.
Reposition selector knob at 1-7/8 and 7-1 / 2 ips (the two extreme
positions) and repeat check as above (3-3/ 4 ips). The c ompens a ting
rod shall enter the knob nest as freely as possible in b oth extreme
positions. Equalize any interference by bending ro d as r e quired.
Place assembly horizontally and check the slack take-up l eve r : The
lever shall have from .010 to .032 clearance between the de lrin tu be
and the
left-hand capstan idler cam. To adjust, insert the tip of
screwdriver in slot at the lower right tab and open it as req u ired.
NOTE:
Use a thick enough screwdriver blade to op en tab so that
it will not nick and/or damage lever; make su re that lever
stays flat.
Actuate play knob back and forth; it should operate free ly.