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Beogram 8000 problem

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fredtr
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fredtr posted on Sun, Sep 27 2020 6:26 PM

I am hoping someone can offer some suggestions regarding the problem I am having with 8000.  Thanks to Martin, I replaced the tach disk and caps, the problem that I am left with I have probably caused.  When I power the unit, after a short delay it spins at 33.33 and does not respond to any of the buttons except to change the speed to 45 and to increase or decrease the speed incrementally.  The processor power on pin does briefly pulse, if I manually extend the time it pulses, 15 volts is removed and the platter stops and then the buttons work normally, but if I press a button that starts it spinning, then I am back to condition when the unit powers on.  If I manually engage the brake (fast down signal to ground) the brake does operate correctly, and stops the platter.  Remove the fast down ground and the platter goes back to spinning at the correct speed.  All control panel buttons are correctly read at the processor.

I like unusual problems, but I am out of ideas on this one.  Any suggestions would sure be appreciated.

Thank-you,

Fred

 

 

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Spassmaker
Top 500 Contributor
North Germany
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Hi Fred

Working on old B&O Gear is always a street paved with unusual problems ;-)

If not already done please check the polarity of the recapped capacitators, maybe twice.

Don´t always follow the printing on the PCB sometimes the printig is not right. Check with the service manual where the Pins of the caps go to the next resistor or transistor.

It took me hours to find a reversed Cap in a Beomaster 6000 4 Ch which shut down after about 2 Minutes making good Music;-((

Look with a magnifier for cold /bad Solderjoints, it´s a common Cause of eratic behavior.

Resolder all Connectors on the PCB.

Is the uPC Voltage ( PIN 30 ) steady 5 Volts?

 

Only a few hints, but sometimes the trouble comes from the simpliest causes ;-))

Good luck and let us know if you had progress.

Best Regards 

Chrischi

fredtr
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fredtr replied on Wed, Sep 30 2020 6:18 PM

Hello Chrischi, Thank-you for your suggestions and encouragement.  I did find the problem, which I did cause.  Like you suspected, as I replaced one of the capacitors I damaged a pad causing an open circuit to the land in one direction.  The result was that the manual lift signal was always held high.  Grounding it resulted in normal operation of the turntable and I traced it back and saw what I had done.  In retrospect, I should have taken your advice and inspected all of the connections to the capacitors I replaced.  

Thank-you again,

Fred

Spassmaker
Top 500 Contributor
North Germany
83 Posts
OFFLINE
Silver Member

Hi Fred

Nice to hear that you could find the problem.

So enjoy some good music.

Best regrds

Chrischi

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