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Old 13th March 2012, 05:11 PM   #41
manina is offline manina  Germany
diyAudio Member
Join Date: Mar 2008
Location: Where the work is
I measured all resistors are are within specs.

The voltage at the emitter is equal between the 4388 of the same side.

While I was measuring, I also adjusted the idling current as detailed in the service manual.

The good news is that the amps seems OK now - it has been up and running for 10 mins without any temperature excursion and stable current draw.

On the other hand, there is a significant difference between the two channels for what concern the emitter DC:
4 mV and 7 mv on the left channel
15 mV on both 4388s of the right channel
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Old 14th March 2012, 12:41 AM   #42
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Join Date: Nov 2003
Location: Louisiana
Did you try swapping the emitter resistor to see if the problem followed the resistor?

How accurate is the meter at low resistance?
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Old 14th March 2012, 08:28 AM   #43
manina is offline manina  Germany
diyAudio Member
Join Date: Mar 2008
Location: Where the work is
No - I have not yet swapped the emitter resistor but I can try this as well.

The meter is a fluke 77 - not sure how accurate it is.
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Old 15th March 2012, 07:57 PM   #44
manina is offline manina  Germany
diyAudio Member
Join Date: Mar 2008
Location: Where the work is
I did few swaps of the emitter resistors without seeing any major changes.

On the other hand, I kept the amp running for nearly 3 hours without any issue. At this point, I'll use an old rule "if works, don't touch it!"
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