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Need BeoMaster 2400 Volume Control Circuit help

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chrismenke
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chrismenke Posted: Thu, Jan 5 2017 8:20 PM

All,

I'm fast running out of things to try on a 2400 which has been recapped and rebulbed with Martin's kits.

The issue is that the volume is pegged up, and won't respond to down commands from the keypad or the remote. This began after I replaced the two large caps in the power supply to quell a hum which existed until the unit was warm.  Due to an obsolete part on the 5000uf caps they were replaced with 6800uf caps per Mouser replacement part recommendation.

Here's what has been done to troubleshoot the issue since:

Recapped the rest of the unit

Replaced the CD4011 IC on the volume control board

Verified the volume control transistors are responding to touch commands

Replaced the rectifier on the main board

Calibrated 15v supply at TP15

I was really hoping the recap would fix the issue and when I got everything put back together it was quite a bummer to find it hadn't.  I'm hoping it isn't something in the LDR...but I've tried pretty much everything I can think of

Thoughts?

 

Dillen
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Dillen replied on Thu, Jan 5 2017 9:00 PM

Check the volume indicator lamps and the transistors related.

Martin

chrismenke
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Indicator lamps are functional (new replacement bulbs).  I've checked the transistors for the the touch pulses.  Which others are 'related'?

Dillen
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Dillen replied on Fri, Jan 6 2017 6:06 AM

The lamp drivers.

Martin

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