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Old 02-27-2020, 06:07 AM   #1
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Join Date: Feb 2020
City & State: Savoie
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Default Harman Kardon PM655 - strange values of voltage


I doing a check in this amp (240v version and the switch is on the 240v ) and saw something strange...
After the schematics (power supply zone) ; instead to have on collector +35.6v for Q5 2SD669 and -35.6 v for Q6 2SB649 i have 40.7v and -40.7v ! For the rectifiers bridges i have 44.8v and -44.8v for both...
For info, all the +/- caps are new ; i even took caps with higher "operating voltage" (if it was given for 16v, i put 25v ...)

Any idea about this difference of 5v ?
Is there someone who spot it too ?

I even asked myself if there wasnt a mistake with the +35.6 and -35.6 v quotes in the schematics for q5 and q6 ^^?!!... Because we can find +44v and -44v in the power driver zone (track come from bridge rectifier) .

...i mean the 4 resistors of 33ohm in the schematics (r19 and r21 for q5 and r20 and r22 for q6) cant block 5v !

What do you think about it ?

Thanks for light about it

Thanks in advance
Attached Files
File Type: pdf Harman-Kardon-PM-655-schematics.pdf (17.00 MB, 2 views)
File Type: pdf POWER SUPPLY ZONE PM655.pdf (167.0 KB, 3 views)
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