Tandberg-TD20A-tape-sm维修电路原理图.pdf
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1、TANDBERG TD 20 A-SE Circuit Diagrams and Alignment Instructions RadioFans.CN 收音机爱 好者资料库 Electrical adjustments TD 20A-SE Make the adjustments in the order in which they are listed here. Many of the adjustments require that previous adjustments have already been correctly made. Clean and degauss the
2、tape path before and after adjustments. lt is assumed that the tape path has already been correctly adjusted as described in the Service Manual for the TD 20A, part No. 714127. Maxell UD XL or equivalent tapes should be used for recording. Necessary equipment - d.c. voltmeter. - 2 high impedance vol
3、tmeters (do NOT use universal meters). - Frequency counter. - Audio generator. - Distortion meter. - Wow meter (required for wow test only). - Test tapes: No. 2 - Azimuth adjustment playback head, 15,000 Hz,7/z ips. No. 3 - Playback cule, DIN 19H,7%ips. No. 4 - Playback level adjustment, 4OO Hz, 7%
4、ips. No. 11 - Speed check, 1000 Hz, 7%ips. Bias Adjustment (front panel) Before adjustment, make sure that the Bias Adjust- ment potentiometers on the front panel are in the mid-position. Checking the oscillator frequency Connect a frequency counter directly to the record head. Adjust the frequency
5、to 123.5 kHz in stereo recording with C313 on the logic board. Then check in mono, left and right, that the frequency are within !.2 kHz. lf outside the tolerance, adjust C303, DUMMY LOAD ADJ. on the audio board. Then check the frequency in stereo and mono left and right. Checking the Bias Adjustmen
6、t (front panel) Connect an audio-generator to LINE 1. Start stereo recording at7%ips speed of a22kHz signal 30 dB below normal recording level (0 dB). Set the Monitor switch to Tape. Check that the output level measured with a.c. voltmeters on the LINE OUT are within approximately + 3 dB to - 5 dB w
7、hen turning the Bias Adjustment potentiometers. Adjustment of EOT/BOT sensor To be performed without tape. Measure with a d.c. voltmeter on pin 3, contact 412 on the logic board. Adjust R422 (on the logic board) to 1.2 V reading on the voltmeter. A , 4 Test Adjustment No. or check Test tape Set the
8、No. deck to Measuring tnstrument Measure atAdjust Correcl readinoSpeedComments 1.1 Azimuth, playback head 2 Playback. c,-r:-.:-. LquoI4oLrvrr. Normal. voltmeters LINE OUTAzimuth screw, playback head Maximum output, see comments 7% iosMaximum output or best compromtse. 1.2 Playback curye DIN 19H 3 Pl
9、ayback. Equal ization: Nomal. a.c. voltmeters LINE OUTPlayback E.Q. adj. R501 /R601 +2dB at 18 kHz 7% ips.Playback curue, DIN 19H, The tape contains the following frequencies: 1000 Hz (reference) 18 kHz, 15 kHz, 10 kHz, 4 kHz, 125 Hz, 40 Hz 1000 Hz (ref.). Ad.iust R501/R601 to + 2 dB at 18 kHz. 1.3
10、Playback tNet 4 Playback. Equalization: Normal or Somial a.c. voltmeters LINE OUTPlayback level R I 69/R269 0.9 volt7h ips. 1.4 Speed11 Playback.Frequency counter LINE OUT! o.5/. 995-1005 Hz in 7% ios. Test taoe No. 1 1 * is recorded at 1000 Hz in 7% ips. Test tape No. l 1 is supplied on a small ree
11、l. This test tape should be spliced into a tape on a larger reel al RadioFans.CN 收音机爱 好者资料库 Tes No. Adiustmenl or check Measuring instrument Measure at Set the deck to Monitor switch ioProcedure 2.1Bias pre-adjustmenvoltmeters LINE OUTRecord. Speed: 7% ipl Equalization: Normal. TapeConnet an audio-g
12、enerator to LINE 1. Set the generator to 1Z.b kHz 30 dB below normal r*ordjng level (0 dB). Adjust RlSl and R251 to maximum outour level. Then turn R151 and R251 counter clockwise to - 2 dB from maximum readino. 11 Azimuth, rsord head a.c. voltmeters LINE OUTRecord. Speed: 77: ip: Equalization: Norm
13、al. Tape Connst an audio-genemtor to LINE t. Start rcording at 7% ips. of a 10O0 Hz signal 30 dB below normal recording level (O dB). Use the voltmeter readings as reference level. Then rmord a 25,000 Hz signal and turn the azimuth screw on the record head to maximum reading or best compromise on th
14、e voltmeters. 2.5Record/ playback curues voltmeters LINE OUTRecord. Speed: 7% ips Equalization: Normal. TapeConnst an audio-generator to LINE 1. Start rmording of a 1000 Hz signal 30 dB below normal recording level (0 dB). Use the voltmeters readings as reference level (0 dB). Then turn the generato
15、r to 12.5 kHz and adiust R151 and B25l to 0.5 dB from the reference level. Turn the generator to 25 kHz and adjust R139 and R23g to 0 dB. Check that the output level do not deviate more than J 2 dB from 20 Hz to 25,000 Hz. Record/ playback curyes voltmetem LINE OUTB ecord. Speed: 15 ips. Equalizatio
16、n: Normal, TapeUse the same recording level as in test 2.3. Use the voltmeters readings as reference level. Check that the output level do not deviate more than 1 3 dB from 20 Hz to 30.000 Hz. Adjust if necessary with PLAYBACK E.O. ADJ. B5O1/8601 and,/or BIAS ADi. R151/ R251. lf re-adjustment is don
17、e, check once again that the output lwel in 7% ips, Equalization: Normal do not dwiate more than r 2 dB from 20 Hz to 25,000 Hz. Adiust if necessary with R139/R239. Record/ playback curyes voltmeters LINE OUTBecord. Speed: 15 ips. Equalization: Special. fapeUse the same recording level as in test 2.
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