Tandberg TCD 310 Mk2 Stereo Schematic

Page 2

ELECTRICAL CHECKS AND ADJUSTMENTS

FOR TCD 310 Mk II

Dolby Board

GENERAL

- 0 d8" level is defined as 775 mV. Thus - 5 dB equals
450 mV and - 35 dB equals 14 mV.

- Make the adjustments in the order in which they are listes

here. Many of the adjustment: require that previous
adjuitmente have already been correctly made. It is
especially important that adjustment for SPECIAL tape
be made before adjustment for NORMAL tape.

- Clean and degauss the tape path before and after the

adjustments. lt is assumed that the tape path has already

been correctly adjusted as described in the Service

Manual for the TCD 310.

m". cm
4%11; ..
A m

Dolby boards Q

Azmurn

C50! 09
plifrn 2 board @ Q Q
R135 mos 205 R235

-l

RJI'I
Amplifier l board

Location of test points and adjustable components

NECESSARY EQUIPMENT

- 2 high impedance Voltmeters (do NOT use universal
meters).

- Frequency counter.

- Audio generator.

- Distortion meter.

- Wow meter (required for wow test only).

- Hum/noise meter (required for signal/noise test).

- Tandberg test tapes No. 21 (1,000 Hz speed test),
No. 22 (3,150 Hz wow test), No, 23 (6.300 Hz azimuth
test) and No. 24 (i .000 Hz playback level).

- TDK C60 SA or equivalent.
- Maxell C60 UD or equivalent.

Adjustment Set the cassette Measuring Measure Correct

No. or check Tape deck to instrument at reading Adjust Comments

1 Record/playback No. 23 Playback Voltmeters OUTPUT Maximum output Azimuth Adjust to best

head azimuth sockets signal. Difference screw on compromise
between the tracks: head
< 4 dB

2 Playback level No. 24 Playback Voltmeters OUTPUT 775 mV R317 (left channel) -

sockets R417 (right channel)

3 Tape speed No. 21 Playback Frequency OUTPUT t 1% - -
counter socket (990 - 1010)

4 Wow No. 22 Playback Wow meter OUTPUT _ g 0.2% __ Measure at end of
(according socket (DIN 45511 tape. Measure both
to peak weightEd) in vertical and hori»
DIN 45507 zontal position.

5 Oscillator SPECIAL SPECIAL Frequency Connect 80 7 100 kHz - Connection is made

frequency Recording counter inductively with a coil or a few
to erase turns of ordinary
head (see wire. Instead of a
comments) frequency counter a
' long-wave receiver
(tuned to 3rd. har-
monic) can be used.
6 Oscillator SPECIAL SPECIAL Voltmeter Across 28 - 32 V 7 -
erase volatge Recording erase head
7 Oscillator SPECIAL SPECIAL Voltmeters OUTPUT g 2 mV ~ INPUT sockets open.

Adjustment Measuring

Nu. or check Tape instrument Measure at Procedure

2 ADJUSTMENT FOR SPECIAL TAPE

2,1 Bias SPECIAL Voltmeters R801 (left channel) Set the cassette deck to SPECIAL recording and adjust
(preadjustment) R901 (right channel C801 (left ch.) and (1901 (right ch.) to readings of

see location" approximately 6-8 mV. (Measure between ground and
drawing the side of the resistor which is connected to the head).

2.2 Recording SPECIAL Voltmeters OUTPUT sockets Set the cassette deck to SPECIAL recording. R1 and R2 to mid-position.
level Connect an audio generator to the INPUT sockets. Adjust the generator

to 400 Hz, a 5 dB (= 450 mV on the Voltmeters).

[- 5 dB is used instead of 0 dB in order to avoid inaccurate results caused
by varying tape characteristics.]

Rewind and play back. The Voltmeters should now read

7 5 dB (= 450 mV) 1 0.5 dB.

11' outside the tolerance, make a new recording while adjusting R105

(left channel) and R205 (right channel) as required. Then play back

and check once more.

2.3 Overall SPECIAL Voltmeters OUTPUT sockets Set the cassette deck to SPECIAL recording. Adjust the generator to - 35 dB
frequency (= 14 mV on the Voltmeters) and record a 400 112 and a 10,000 Hz
response signal at this level.

(INN) Rewind and play back. Use the 400 Hz signal as a reference and check on
both channels that the 10.000111 signal is within the following tolerance:
- 0 dB to + 5 dB.
If outside the tolerance adjust C801 and C901 (bias). Then make a new
recording, play back and check once more.

2.4 Distortion SPECIAL Distortion OUTPUT sockets Set the cassette deck to SPECIAL recording. Generator to 1000 HZ, 0 dB

meter (= 775 mV on the Voltmeters).
Rewind and play back. Check that the distortion is=< 3%~
lfoulside the tolerance adjust C801 and C901 (bias), Make a new
recording, play back and check once more. Then repeat step 2.3

2.5 Overall SPECIAL Voltmeters OUTPUT sockets Set lhe cassette deck to SPECIAL DOLBY (I) recording: Adjust the
frequency generator to ~ 55 dB and record the following frequencies: 400 Hz,
response (check 55 Hz, 1000 III, 4000 Hz, 10,000 Hz, 14,000 HZ.

With 0) Rewind and play back. Use the 400 Hz signal as a rererunee, and check
that the other signals are within the following tolerances:
551121-3d3to62d3 _ 10,000 Hz: 0dB to+5dB
1000 Hz 21115 to +2 dB 14,000 Hz: ~2dB to+5dB
4000 HZ . 2 dB to +4 (13
lfoutside the tolerances try changing the values of C501/C502 (left ch)
and C601/C602 (right ch). Increased values give higher treble response.

2.6 Indicators SPECIAL Indicators Record a 400 Hz, 0 dB signal and adjust R135 (left ch) and R235 (right

ch) to 0 dB deflection on both indicators.

3 ADJUSTMENT FOR NORMAL TAPE

3.1 Recording NORMAL Voltmeters OUTPUT sockets Same as in step 2.2. except that the SPECIAL button is released.

1" lfoutside the tolerance adjust R104 (left ch) and R204 (right ch).
DO NOT TOUCH R105 OR R2051
NOTE! Adjustment of R104 and R204 will not affect the readings on the
indicators of the cassette deck,

5.? Overall NORMAL Voltmeters OUTPUT sockets Same as in step 23, except that the SPECIAL button is released.
mum If outside the tolerance adjust R807. DO NOT TOUCH cam OR c901.
response
(adjustment)

3.3 Distortion NORMAL Distortion OUTPUT sockets Same as in step 24, except that the SPECIAL button is released.

meter Is outside the tolerance adjust R807. Then repeat 32.
DO NOT TOUCH C801 0R C901.

3.4 Overall NORMAL Voltmeters OUTPUT sockets Same as in step 8.5, except that the SPECIAL button is released. Tolerances:
frequency 55 HZ: - 3 dB to +2 dB 10.000 Hz: - 2 dB to +5 dB
response (check 1000 Hz - 2 dB to #2 dB 14,000 Hz: - 3 dB to *4 dB
with DOLBY) 4000 Hz: - 2 dB to +4 dB

If outside the tolerances try changing the values of C503/504 (left oil)
and coca/cam (right ch). Increased values give higher treble response.

3.5 Erasure SPECIAL Voltmeters OUTPUT sockets Record a 1000 Hz, 0 dB signal. Rewind and erase. Then rewind once

more and play back the erased piece. The Voltmeters should read
< -- 62 dB.
3.6 Signal/noise SPECIAL Hum/noise OUTPUT sockets The signal/noise ratios at 3% distortion should be at least as good as
and meter specified in the table below:
NORMAL (:ccording uotav rm. OFF on
Sllmlhlpl noun: NORMAL HECIAL NORMAL SPECIAL
DIN 45405) om 456" (Gerhnebaolmrunl) u dl as dl so do as ea
DIN 45511 Irwin-nun.) u do u as so dl an d!