Service manual

STP 11-25R13-SM-TG
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Performance Steps
(6) If the ATR shuts down shortly after entering any mode, check for a missing or stretched
tape counter drive belt or a defective reel rotation sensor.
( a) Tape eating protection circuits can shut down the ATR improperly due to a lack of
reel sensor pulses.
( b) A related symptom will be that the tape counter does not change during the period
when the tape is moving.
(7) If the logic is not properly controlling the various solenoids or other actuators in a soft
touch deck, consult a service manual to continue further.
b. Check for electrical problems.
(1) If the capstan speed is not working, check the voltage regulator or the capstan itself.
(2) Check the erase and bias oscillator using a blank tape.
( a) Record a 1 kHz tone from the ATSG to check the record head amplifier.
( b) Erase the 1 kHz tone to check the erase and bias output network.
(3) If prerecorded tapes or tapes recorded on another ATR sound muddy, the azimuth
alignment of the suspect ATR may have shifted or be misadjusted.
NOTE: If the angle is not exactly 90 degrees, high frequencies will reduce in amplitude during playback
of a tape not recorded on this ATR. Similarly, a tape recorded on an ATR with an improper azimuth
setting will sound muddy on a properly adjusted ATR.
( a) To determine if azimuth alignment is the problem, RECORD some music and
immediately PLAY it back. If this recording sounds fine but sounds muddy on
another ATR, improper azimuth alignment is the likely cause.
( b) If the recording still sounds muddy, the ATR may have electronic problems like
excessive bias (check to ensure you have selected the proper type of tape or bias
setting), a worn record or playback head, or magnetized parts. However, dirty heads
as well as other mechanical problems can also result in weak muddy sound.
(4) Localize intermittent power or sound problems.
NOTE: Check tape transports for actual tape speed, operation, or sound quality.
( a) Check for broken solder connections where the power plug joins the circuit board
inside the ATR by wiggling the plug without moving or flexing the cable itself. If the
sound cuts in and out, or the tape player starts and stops, there is likely a bad
connection here.
( b) Eliminate the possibility that the AC adapter or headphone cable is bad by wiggling
and tugging on the cable while holding the plug steady.
( c) Verify that it is not simply a matter of dirt or grime interfering with a good connection.
(5) Troubleshoot a dead playback channel.
NOTE: This could be a bad playback head, a bad connection, or a bad component in the playback
electronics.
( a) Confirm that the problem is not in the headphones, patch cables, or the remainder of
the audio system; try an alternate audio source where possible.
( b) Gain access to the terminals on the playback head to determine if the playback
circuitry is working.
( c) While the ATR is supposed to be playing, touch the end of a jeweler's screwdriver
gently to each of the four terminals in turn.
NOTE: When touching the good channel, the appropriate speaker buzzes. If touching one terminal and
a buzz is heard from the dead channel, that channel head is possibly bad. If touching two terminals and
both channels buzz, the ground connection to the input preamplifier has likely fallen off. If you hear
nothing from the bad channel, an electronic problem is likely in that channel.
( d) Bad connections aside, the most common problem area would be the audio amplifier
(such as a bad IC or capacitor).
(6) Troubleshoot a distorted or erratic recording.
( a) Determine if it is a record or playback problem.
NOTE: PLAY a tape recorded on another ATR or a commercially prerecorded tape. PLAY a tape from
this ATR on a known working ATR.
( b) If record is the problem with very distorted sound, check for a bad bias oscillator,
switching circuit, or record switch.