Beogram 6006 start problem

david winter

Classical music lover.
Hi,

I'm trying to figure out why this Beogram 6006 won't start as it should.
I recaped the main board (some caps were out of specs as usual).
Carbon resistors were checked as well. I then did a first test and here's what happens:
After pressing Start, the optical arm lights up (cleaned the sensor) and the platter spins correctly and 33.33 shows on the display.
The linear arm moves at correct speed towards the platter but will stop after only for 3/4" (about 2cm) and then go back to stand-by position at lower speed, as if the record ended.
I checked the arm motion for possible mechanical blockings by spinning the feedscrew manually, but I found no problem. Also, there is enough belt tension between the motor and the feedscrew.

Anybody has an idea of what's going on ? The service manuals can be found here.

Thanks.
 
Hello. I'm no expert on the Beogram 6006 (or its close cousin, the 8000, which I own two examples of), but my guess is that it has something to do with the pulse sensor. The feedscrew has a bladed shutter on the end which passes between a photosensor and an IR emitter, IIRC. This sends pulses to the microcontroller to tell it that the arm is moving (four pulses per revolution of the feedscrew, IIRC), and to give it an idea of the position of the arm along the record (to facilitate the pause function). If the microcontroller isn't seeing those pulses, it may think that the arm isn't moving (or isn't able to move), and to return to rest.

I've seen this happen when the stylus gets caught in a lockgroove (either in the middle or at the end of a record), though this generally takes a couple of minutes. Maybe it's more sensitive to stoppage of pulses during the start of playback. In any case, I'd check either the sensor or the light, and see if one or both have stopped working. Also, there are lights (and sensors) under the arm assembly involved with keeping the tonearm tangential during playback; perhaps one of those has failed. Good luck!
-Adam
 
I saw a post about this and scoped the output of the two op-amps taking the signal from the IR sensors. No problem on that side.
Also remade lots of bad looking solders on all connectors. Didn't help more.
Checked light sensors of << and >> switch. Can't get the 610mV as suggested and stays at 1.7-2V or so after pressing Play even if I try to adjust screw B or A to change the amount of light going to the photoresistors.
 
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