Beogram 8002 – Power on/off signal

[Doc99]

I’m working on my Beogram 8002. Just finished replacing the electrolytic caps. The platter does not turn. If I press a speed button, the speed selected does show up on the LED display. The +15 and -15 supplies do not turn on. Traced it to the power on/off signal that comes from the uP.  Checked and there is continuity (3.3K) from the power on/off transistor TR21 back to pin 38 of the uP.

Does anyone know if there are other signals that must be present for the uP to bring the power on/off signal low?

Thanks,

Doc

[Mark-sf]

Are you getting a voltage change when you press start on pin 38? Do you have 5v on the collector of TR21? I would also double check your replaced cap polarities against the schematic (not the board).

• This reply was modified 2 days, 6 hours ago by Mark-sf.

[Doc99]

TR21 is on as I’m seeing 0.6V on the base and the collector is close to gnd. The collector at gnd is forcing off the +-15V. Good idea to try and pull the base of TR21 low and see if the +-15 turns on. That probably waits until next weekend. In the meantime I’m bring the board into work. I used a hand magnifier when reworking and feel pretty good about not causing any shorts or opens, but will check with a microscope. I marked the negatives on the board as each cap was replaced. However, will check just in case.

Thanks,

Doc

[Doc99]

Maybe I’m missing your point about asking about the start button. I am not ready to test the tone arm movement. I am using the 33 or 45 button to start the platter. Is the +-15 not needed for platter rotation?

[Mark-sf]

The motor circuit requires the 15v supply to operate. The TURN button is used to rotate the record for cleaning, not the 33 speed button as was the case on the older models. The 45 button never turned the platter.

 

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