Ampro 745 Career User manual

PnoToFACT* FolJrt AMPRO
MODET 745 "Coreer"
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GENERAL INFORMATION
The Ampro Model 745 is designed to record and play back two tracks of material on
standard width recording tape, which doubles the playing time of a reel of tape with no loss of
frequency response or quality. Recordings can be made from a radio, television receiver or
phonograph, in addition to those made directly from the microphone. Recordings can be played
backthroughthe self-contained speaker or an external speaker through use of the Speaker Jack.
The Model'745 has two tape speeds, 3 3/ 4" and ? I/2" per second. Using both tracks of
the tape the recording time is as follows.
Size Reel 3 3/ 4" Speed
5" reel (600 ft. ) I hour
7" reel (1200 ft. ) 2 hours
7 I/ 2" Speed
/2 hour
I hour
This unit is designed to operate on 60 cycie, 115 volt, AC supply only. Before connecting
to your line supply, be absolutely certain that it agrees with the above specifications.
Manufactured by:
Ampro Corporation
1345 Diversey Parkway
Chicago 14, Illinois
fhis molerial compiled ond published by
5AM5 & CO., lNc., INDIANAPOLIS,
Copyright 1952 . All Rights Reserved
0ATE l0 - 50
INDIANA
srT 333 FOLDTR 3
HOWARD \N.

Figure I
OP ERATING INSTRUC TIONS
Prepartion For Operation-
1. Remove the AC power cord 5" reel of tape,
empty reel and microphone from the rear storage
compartment.
2. Plug the AC cord into a convenient wall recep-
tacle of the proper rating.
3. Be sure the Play-Stop-Rewind control is in
I'stop" position and the Play-Record control is in "playt'
position,
Speed Change Knob-
Select tape speed with the unit on. Moving switch
upwardwill cause the unit to play at the speed of 3. 75,
movingswitchdownwardtheunit will play at a speed of
?.50. For maximum tape economy or for recording
the spoken voice, 3. ?5 I. P. S. is suggested. The best
for music and maximum fidelity is the speed of ?. 50
I. P. S.
Threading The Tape-
1. Place a full reel of tape on the left (supply)
spindle (37), makingcertainone of the reel slots catch
the protrusions of the pan. Unwind about 14't of tape
from the supply reel.
2. Insert free section of tape into the tape slot.
Page 2
3. Insert free end of tape into one of the three
slots in the hub of the right (take-up) reel and while
holding the tape in place give the reel two or three
turns until the tape is secured.
4. The dull side of the tape should always face
away from the operator (rear of unit).
To Record From Microphone-
1. Turn the On-Off Volume control to the right
until a click is heard and allow about 30 seconds for
the unit to warm up.
2. Insert the microphone plug into the "Micro-
phone" input.
3. Press down "Safety Buttonil and turn Play-
Record control to "Mic. Recordil position.
4. Adjust the '"V'olumet' control until the Record
Level Eye, greenrays almost meet on loudest sounds,
recording level is perfect at this point.
5. The "Tone" control does not operate during
recording. When recording from radio, set the radio
"Tone" control for maximum treble.
ToRecoriFromExternal Radio. TV. Or Phonograph-
1. You may record directlyfrom the speaker by
using the special radio-phono connection cord, avail-
ableasaccessoryNo. 108. (This cord has a telephone-
type jack at one end, andtwo metal clips at the other).

Figure 2
2. Attach one clip to the ungrounded side of the sired listening level.
radio, TV or phono speaker coil. The other clip is
attached to the grounded side of the coil. 6. To stop, return Play-Stop-Rewind lever to
t'Stopt'.
3. Plug the Jack into the receptacle on side of
your unit marked I'Mic or Phono, r' and proceed as Fast Forward Tape Advance-
described under "To Record From Microphoner'. 1. Leave Play-Stop-Rewind lever in ilStopil po-
NOTE; Remove patch cord after recording is com- sition.
pleted.
To Use Second Track-
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1. Move Play or Record-Stop-Rewind lever to
the "Stop" position when all the tape has wound onto
the take-up reel.
2. Remove reel containing tape and place on
left-hand supply spindle.
3. Place empty reel on right-hand take-up
spindle.
4. Thread tape as previously described.
To Play Recordings-
1. Turn on unit with "Volume" control knob.
2. Thread tape as described under ilThreading
The Tape.
3. Set the speed change knob (tA)to the speed at
which the recording was made.
4. Turn Play-Stop-Rewind lever to play.
5. Adjust "Volumef' and "Toneil controls to de-
2. Hold down "Fast Forward Buttont' (6) on top
of right reel spindte (?).
3. Release when tape has advanced to location
on the tape you wish to hear or record.
To Rewind-
1. Before rewinding, return Play-Record con-
trol to "Play" position.
2. Turn Play-Rewind lever to "rewindr'. Re-
wind tape to beginning of your recording and return
lever to stop.
To Edit And Splice Tape-
NOTE: Since it is impossible to edit and splice one
track without affecting the other, recordings
which are to be edited should be limited to
one track only.
1. The tape maybe editedby cutting out unwanted
portions, or joining selections into another sequence"
Announcements may be inserted between selections,
etc. Unused sections of tape can be spliced together
for re-use.
Page 3

2. Forbestresults, cuttape at a slight diagonal,
join ends together with splicing tape on the glossy side
and trim off any excessive width.
E rasing Recorded Material-
When the Play-Record knob (3) is in the "Record"
position, the erase head is automatically in operation,
erasing any previous recording before a new one is
made. You may erase material no longer needed,
without recording, by moving the Play-Record knob
(3) to "Record" on turning the "Volume" control knob
to the minimum volume position just before the record-
er shuts off. Onetrack is erased at a time, To erase
the second track, reverse the reels and repeat the
above operation.
To Use Recorder As A Public Address System-
Plug microphone cord into I'Mic. or Phonoil re-
ceptacle. Turn Play-Record controlto I'phono-record"
position. Be sure microphone is far enough away from
speaker to avoid feedback squeal. Volume may be ad-
justed with Volume eontrol. Mikeand/or radio-phono
can be simultaneously used for blending of special
effects in public address use with Ampro Dual - Input
Mixer, No. 133.
ELECTRICAL ADJUSTMENTS
Erase Head Adjustment-
I, Loosen screws located on the left side of
erase head and raise or lower head and tilt head as
required in order to obtain minimum output.
2. Then loosen screw (32A) and rotate position-
ing block for minimum output.
3. Tighten screw (32A) and rotate positioning
block for minimum output.
4, Checkfor oppositetrackerasure if excessive,
head is set too low.
Record Head Adjustment-
The record head is mounted on a pivoted plate
which is held in place by two filister head screws
(32B) located at opposite corners of the plate. Tight-
ening or loosening the screw on the left (viewed from
operating position) rocks the pivoted plate thereby
changing the angular relationship between the gap and
thetapeand increasing or decreasing the compression
oI the spring located under the head of the opposite
mounting screw. In order to make an adjustment,
threadtherecorder with pre-recorded 1 mil alignment
tape or a good recorded tape on the machine.
Connect an output meter across the terminals of
the elliptical speaker. Switch recorder to "play" po-
sition and set the volume control to the 12 o'clock po-
sition. Rotate the screw which secures the left side
of the plate in order to obtain maximum output from
the pre-recorded material. Make a rough adjustment
at a tape velocityof 3. ?5 inches per second the switch
to ?.50 inches per second for final adjustment.
NOTE: Watch out for a false peak you may find 3
peaks - be sure to adjust for strongest peak.
Page 4
Erase Current-
Disconnect the ground lead at the erase head
terminal and insert a 10 ohm non-inductive resistor.
Qonnect a VTVM across the resistor. Switch to
record and note voltage. Correct voltage will be ap-
proximately 0,4-0. 5 volts indicating an erase current
of approximately 40-50 ma.
Bias Current-
Disconnect lead from record head. Insert 100
ohm non-inductive resistor between red lead and re-
cord head terminal and connect VTVM acrossl00 ohm
resistor. Turnvolume control to low volume position.
Switchtorecord and measure voltage across resistor.
Voltage shouldbe "0.40 - 0,45" volts which is equiva-
lent to a current of "0.40 - 0.45 ma. If bias is not
within these limits adjust slug in oscillator coil to
obtain correct current.
MECHANICAL ADJUSTMENTS
Erase Interlock Cam Adjustment-
l. Loosen set screw slightly so that cam (34)
can be turned on control shajt.
2. Turn shaft to maximum clockwise t'Playt'
position. Rotate cam so that flat surface is parallel
to edge of interlock spring (35).
3. Press in on interlock spring, then turn con-
trol shaft in order to expose setscrew. Tighten set-
screws.
Rewind-Play Or Record Cam (29) Adjustment-
1. Turn control shaJt to maximum counter-
clockwise (Play or Record) position.
2. Loosen setscrews in cam. Rotate cam so
thatcamflatis parallel to flat surface of pad actuating
arm (24).
3. Raise or lower cam (29) as required in order
to locate top face of cam in the same plane as top of
arm (24). Tighten setscrews.
4. Place light film of "Lubriplate" on surface
of cam which comes in contact with arm (24).
Disassembly Instructions-
1. Take outthe four Phillips filister head screws
located at the corners of the panel (5). Loosenthetwo
allen setscrews in the "Rewind-Play or Recordl knob
(3) and remove the knob. Puli off the other three
knobs (2). Lift off the control panel (5).
2. Removethreephillipsoval head screws which
hold speed change control cover (l) in place and lift off
cover.
3. Take out ten phillips oval head wood screws
which hold metal panels to case.
4. Loosen cable clamp which holds line cord to
back of carrying case. Standrecorder on end and pull
mechanism out of case.
Takeup Brake Adjustment-
Place "Rewind-Play or Recordtt knob in [Playtt
t-

0
Figure
position. Loosen locknut on adjustment screw (19A)
andturn screwto provide a clearance of I/ 64" between
shoe (19) and tire (8). Tighten locknut.
Feed Spindle Brake Adjustment-
Place t'Rewind-Play or Record" knob (2) in
"Play" position. Loosen double nuts at end of brake
rod (48). Adjust nuts to provide a clearance of L/ 32"
between shoe (67) and tire (?0). Rotate feed spindle
and check to make sure that eccentricity, if present,
does not reduce clearance below minimum value of
L/ 32". Tighten locking nut.
Instant Stop Link-
Set inner nut of link (14) L 5/ 32* from end of
link (14). Set outer nut flush with end of tink.
Rewind Adjustment-
Place "Rewind-P1ay or Recordil knob in ftPlaytt
position. Loosen double nuts at end of pushrod (30).
Adjust nuts to provide a clearance of L/ 64 between
rewind drive belt (ab) and knurled section of drum (69).
NOTE: If rewind does not function properly, and the
rewind belt (45) is not damaged, the trouble
is probably due to excessive take-up tension.
Takeup Adjustment
1. Cement 8-10" of tape or string to the hub of
a ?" reel. Place reel on takeup spindle and hook a
spring balance scale (0-8 oz. or 0-16 oz) to the loose
end of the tape or spring. Switch recorder to trplayrr
3
measure the takeup tension-'correct tension should be
l/2toLoz.
2. lf. takeup tensions are incorrect, remove
recorder from case. Loosen two setscrews which
hold the intermediate drive putley (47) to takeup drive
spindle and pull out spindle assembly.
3. Grasp the spindle by the shank (9), hold
spindle in a vertical position with the reel drive pins
on top. Hook the spring balance scale to one of the
reel drive pins and pull along a line as a right angle
to a line thru the center of the spindle post and pin.
The "breakaway"tensionrequired to rotate the spindle
should be 3 to 5 oz. In order to adjust t}re tension,
invert the spindle and insert the ends of the jaws of a
pair of longnose pliers into the two holes in the clutch
pressure plate (12). Turn the plate to the right to
increase the tension.
NOTE: Thisadjustment is sensitive when making ad-
justment, do not turn the plate more than the
width of one of the holes between tests.
TROUBLES
Whining Or Scrapping Noise-
1. The recorder is shifted in the case, the bottom
end of the motor shaft rubs against the guide sleeve in
the bottom cover and produces the noise.
2. Reposition the mechanism in the case and
tightenthe retaining screws. If theholes in the support
blocks are damaged, the best way to make a permanent
repairisto inject plastic wood into the hold before in-
serting the screws.
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A PHOTOFACT "EXPLODED" VIEW
O Howard W. Sams & Co', lnc' 1956
Figure 4A. Exploded View Of Parts Above Baseplate.
Page 6

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A PHOTOFACT "EXPLODED" VIEW
@ Howard W Sams & Co., lnc. 1956
Figure 48. Exploded View Of Parts Below Baseplate.
Page ?

Fails To Record-
l. Tapepressurepads (25) notadjusted properly,
resulting in thetapenot being held against the record-
ing head. See "Rewind - Play Or Record Cam Adjust-
mgntt'.
2. Check the recording tape to see if the dull
coated side faces inward on the reel. If the dull side
faces outward a recording cannot be made.
Tape Overruns Or Spills When Knob (3) Is Turned To
Stop, During Rewind Or Fast Forward-
l. Brake shoes out of adjustment. See Takeup
and Feed Reel Brale Adjustments.
2. Rods (30 and 48) loose are not adjusted
properly.
Speed Variation Or Wow-
1. Check the capstan (52), pineh roller (15),
motor pulley (55), and ftywheel (52) for oil or foreign
material on their driving surfaces. Clean these parts
witl a good cleaning fluid.
2. Checkmotorpulley(55) to see if it is secured
to motor shaJt.
3. Flatspoton rubber roller (15) not smooth and
even, replace part.
4. Pressure Pad assembly (24) applyingtoo much
pressure against tape. Check adjustment under
'Rewind-Play Or Record Cam (29) Adjustment. rt
Incorreet Indexing Of Function Knob (2)-
l. The control knob (2) is in Play position the
safety interlock button (5A) prevents the shaft from
turning.
2. If the operator forces the knob, thereafter,
it will not index correctly.
3. Pull of the knob and drive down a wedge,
tlereby expanding the shaft, then place the knob in the
proper position and push down onto the shaft.
No Drive In Fast Forward-
1. Belt (46) loose or broken, thereby when button
(6) is depressed fast forward is in-operative.
2. When button is depressed the felt clutch (11)
does not make contact, adjust takeup as described
under "Tal<eup Adjustmentr'.
No Rewind-
1. Rewind belt (45) broken or loose.
2. Push rod (30) not properly adjusted, check
adjustment under'Bewind Adjustment".
3. No Rewind can be caused byexcessive takeup
tension. See "Takeup Adjustment".
Speed Change Knob Fails To Change Speed-
1. Setscrews in speed change lever (76) loose
causing lever to move on shaft,
2. Belt shifter (54) notadjustedproperly. Check
to see that shifter moves belt (53) up and down on pulley
(55).
Erase Current Too Low-
l. Some 6AQb tubes did not deliver full output as
oscillators. The cathode resistor was changed from
1500 ohms to 1200 ohms in order toinsure satisfactory
output from all tubes.
MAINTENANCE
Cleaning The Play-Record Head-
The play-record head is subject to an accumu-
lation of tape coating residue which is worn off the
tape as it passes the head. This shouldbeperiodically
removed since it may cause faint recordings and poor
playback. Wipe off the record head contact surfaces
carefully with a clean cloth. If dirt is caked or hard
and will not come off with a dry cloth, dampen the
cloth slightly with water.
NOTE: Do not use a brush or excessive amount of
water on the head surface.
LUBRICATION
All rotating parts are provided with generous
size oilite bearings, which are factory lubricated and
require no further attention, An occasional cleaning
out of foreign matter under the plastic cover (5) is
desirable.
Page 8

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