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Old 22nd December 2008, 10:55 AM   #7801
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Quote:
Originally posted by neychi
Hi!

I finaly finished my Krell, but i have a problem. I can't adjust bias across emiter resistors. I have zero V and trimpot does not working on boat channels. DC offset was no problem to set, and I even listen to some music and sounds good, but bias adjustment doesnt working. I have Jan's boards with corrected traces, 2sc3955 for bias transistor. Any idea?

Thanks

Dean
There was some mistakes on the PCB, did you follow the instructions for correcting it?
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Old 22nd December 2008, 11:00 AM   #7802
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Quote:
Originally posted by neychi
Hi!

I finaly finished my Krell, but i have a problem. I can't adjust bias across emiter resistors. I have zero V and trimpot does not working on boat channels. DC offset was no problem to set, and I even listen to some music and sounds good, but bias adjustment doesnt working. I have Jan's boards with corrected traces, 2sc3955 for bias transistor. Any idea?

Thanks

Dean
There was some mistakes on the PCB, did you follow the instructions for correcting it?
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Old 22nd December 2008, 11:04 AM   #7803
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What value resistor did you use for R124?
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Old 22nd December 2008, 11:06 AM   #7804
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Did you connect Q111 correct way round?
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Old 22nd December 2008, 11:09 AM   #7805
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Transistor Pin-out
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Old 22nd December 2008, 08:26 PM   #7806
neychi is offline neychi  Croatia
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Hi Nico!

Yes, I corrected the traces, value for R124 is 4k7 and Q111 is connected ok.

Regards
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Old 23rd December 2008, 02:16 AM   #7807
john65b is offline john65b  United States
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EDIT - I had Pinkmouse boards, so my response below may not apply...

I had a similar problem... read here

here

Turns out my output base resistors (R501 - R503 and R507 - R509 on PM board) were 2.2K ohms and not required 2.2 ohms.

Also make sure the signal ground is connected correctly - had an issue here too that made it difficult to set DC offset and Bias...
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Old 23rd December 2008, 03:07 PM   #7808
neychi is offline neychi  Croatia
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Base resistor are 2R2, I checked, and signal ground is fine. I adjust DC offset without any problem to 0V.
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Old 23rd December 2008, 04:03 PM   #7809
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Quote:
Originally posted by neychi
Base resistor are 2R2, I checked, and signal ground is fine. I adjust DC offset without any problem to 0V.
YOU ARE SURE THAT YOU ARE MEASURING BETWEEN OUTPUT (SPEAKER LIVE) TERMINAL AND OUTPUT TRANSISTOR EMITTER. WHAT IS THE BIAS CURRENT YOU ARE MEASURING?
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Old 23rd December 2008, 04:58 PM   #7810
AndrewT is offline AndrewT  Scotland
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and what is the voltage across the driver emitter resistor?
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