Problems with B & O BeoCord 9000
I got an old BeoCord 9000 deck almost for free. The head and the mechanics looks very well and only the belts needed replacement. So I did replace them. After that tested the frequency responce for playback and recording after calibration. To my surprise I found it is very very crappy. The high frequencies of the recorded tape are attenuated strongly and also there is a lot of noise including some secondary frequencies showing up from nowhere when recording simple sinusoidal oscillations higher than 15 KHz. This is after I performed the automatic calibration routine.
I looked at the manual and decided to inspect the playback amplifier so I connected an oscillator to the PB amplifierand connected the output of the PB amplifier to my scope as explained in the service manual. I expected to see frequency responce of the PB amp above 21 KHz as the manual explains. However, the highest measurable frequency was 21 KHz. After that the responce falls apart and can see only noise. I tried some tuning following the procedure in the service manual but with no luck the freq responce ends at 21 KHz and that's it while according to the manual it should be flat up to at least 25 KHz.
Then I tried to calibrate the record amplifier as explanied in the manual but with no luck - the frequencies above 15 KHz are attenuated quickly and also there is a lot of noise.
I wonder what could be the resason for these problems and if it worth at all the time trying to salvage this deck. Next I was thinking to check all eletrolythic caps for ESR and replace the flawed ones. I will appreciate any input regarding this.
Thanks
Dimitar
I got an old BeoCord 9000 deck almost for free. The head and the mechanics looks very well and only the belts needed replacement. So I did replace them. After that tested the frequency responce for playback and recording after calibration. To my surprise I found it is very very crappy. The high frequencies of the recorded tape are attenuated strongly and also there is a lot of noise including some secondary frequencies showing up from nowhere when recording simple sinusoidal oscillations higher than 15 KHz. This is after I performed the automatic calibration routine.
I looked at the manual and decided to inspect the playback amplifier so I connected an oscillator to the PB amplifierand connected the output of the PB amplifier to my scope as explained in the service manual. I expected to see frequency responce of the PB amp above 21 KHz as the manual explains. However, the highest measurable frequency was 21 KHz. After that the responce falls apart and can see only noise. I tried some tuning following the procedure in the service manual but with no luck the freq responce ends at 21 KHz and that's it while according to the manual it should be flat up to at least 25 KHz.
Then I tried to calibrate the record amplifier as explanied in the manual but with no luck - the frequencies above 15 KHz are attenuated quickly and also there is a lot of noise.
I wonder what could be the resason for these problems and if it worth at all the time trying to salvage this deck. Next I was thinking to check all eletrolythic caps for ESR and replace the flawed ones. I will appreciate any input regarding this.
Thanks
Dimitar
I do not remember very well the methodology of calibrating this machine but I believe you have followed the traditional procedure:
1-Check all mechanics to be in order, clean & demagnetize the heads etc...
2-Adjust PB amp with a calibration test tape (ie 120uS Normal), PB Level @ 0dB and HF EQ at -20dB for best flat FS @ -20 dB, and check the azimuth of PB head @ 10kHz.
3-Adjust bias (for tape in use recommended bias) and the REC amp HF EQ @ -20dB for best flat FS (ie 120uS Normal) @ -20 dB. If it has a seperate REC head adjust its azimuth @ at 5 & 10 & 15 kHz and recheck FS.
4-Adjust REC Level for 0dB.
If step 3 is an auto procedure, check it, for proper operation.
Give it a chance.
1-Check all mechanics to be in order, clean & demagnetize the heads etc...
2-Adjust PB amp with a calibration test tape (ie 120uS Normal), PB Level @ 0dB and HF EQ at -20dB for best flat FS @ -20 dB, and check the azimuth of PB head @ 10kHz.
3-Adjust bias (for tape in use recommended bias) and the REC amp HF EQ @ -20dB for best flat FS (ie 120uS Normal) @ -20 dB. If it has a seperate REC head adjust its azimuth @ at 5 & 10 & 15 kHz and recheck FS.
4-Adjust REC Level for 0dB.
If step 3 is an auto procedure, check it, for proper operation.
Give it a chance.
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