2270 receiver bad DC offset and bias

gkOne

New Member
Hi all,

Had a short from right amp output transistors a while back and managed to fix that by basically replacing the pair and also R786/787 parts. Did some spot component checks on the rest of the board inclundig the driver transistors and some doubtful soldering and went on with replacing some transistors, resistors and diodes on the power amp that was also giving issues of its own. Used my DBT to power up this morning and the receiver lit up nicely, with a nice dim glow from the DBT. No relay click at this pint though. Removed the DBT and powered up again, all good and relay clicked after a couple of seconds. Thought I'd
check on the power board DC voltage and speaker terminals at that point.

Got 44 VDC on my meter which i tried to adjust down to 35 VDC per the SM but I couldn't trim it down via the trimmer resistor which tunrbed left or right didn't make any difference at all.

With that I checked on the right amp speaker terminals and got a whopping 5.95 VDC that was nowhere near to zero and again, the trimmer resistor on the amp side did not seem to trigger any change at all.

Strange thing though, the relay clicks out of protection, albeit a couple of seconds delay, and seem to stay there though I didn't leave tte receiver on for a long period of time as si was afraid some bad would happen next.

Finally, plugged my headphones through the front jack and got a loud continuous buzz desoite the volume control all the way down.

I think I may need help!

Many thanks in advance for the direction and advice provided.

G

PS: read on of the threads here that H762-763 might need replacement and I thought i'd replaced all four H762 through HH765. Any well known replacements/subs for those ?
 
Typo... The other parts replacement that I did was on the power board P800, not the power amp as I wrote.

Thanks
G
 
you may have been caught out by an error in the manual .
looking at schematic you set voltage by putting meter probes on j804 and j805 ..j805 is ground .
adjust to 35v with r806
 
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