ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi.
Aquired an old Beocord 9000.
Have fixed "the usual" problems: Dead segments in the display and non-existing rubber-belt.
Plays back fine but I have a problem when it comes to calibration. Auto REC-CAL works but left channel does not sound ok when recording.
I have tried to calibrate via the servicemanual but I am missing a couple of points:
3-1: Azimuth correction: OK
3-2: Play back level (Dolby level): OK (580 mV in both channels using A.N.T. Audio U04103-70A calibration tape
3-2: PPM calibrated OK
3-4: skipped
3-5: 15 kHz Boost skipped
3-5: Cal detector and oscillator calibrated to 2.95V
3-6:17 kHz oscillator ok
3-6: 7 kHz oscillator ok
3-6: Bias amp and filter: Minimum deflection is not the same on the 2 channels - approx 8V and 7.5 V. Cannot calibrate to same voltage
3-7: Bias right ok
3-7: Bias left ok
3-7: Right sensitivity ok
3-7: Left sensitivity NOT ok - NO STORE LED lights up all the time - cannot adjust 3R230 to turn off NO STORE LED. Could IC201 (4066) be the culprit?
3-9: When checking the control diagram I get values like 10-10-4-10-5, meaning left sensitivity is far off specs.
Studied the diagram (PCB3) closely, but don't know where to start the fault finding.
Bonus info: All capacitors on PCB3 has been renewed. Trimmers checked and seems fine. All connectors has been resoldered. Using TDK SA-X for recording. Tape transport and heads cleaned and looks fine.
Anyone has an idea ?
Best regards Thomas.
No hints anyone ?
Normally I would try to help but I am swamped with other projects right now and can't open one of my BC9000 units to check. In your case you have a working right channel so I would suggest trying to isolate where the problem originates...possibly by going through the various stages and compare the left and right channel signals. That's all I can think of at the moment.
-sonavor
Always difficult to diagnose from a distance, particularly on a machine as complex as this, but;Never judge the calibration routine without the metal bottom plate fitted to the Beocord.Without the shielding provided by the bottom plate, it may even end up showing wrong tape type.
Will it record and playback in fair quality if calibration is not first run? In other words - are the "common" signal paths OK?If they are good, it could point to a problem in the signal paths to - and from the calibration - or a problem with the controlling outputs from the calibration circuits.
Martin