Sony STR-V3 bias help

dukeofurl

Active Member
Got a Sony STR-V3 receiver that needed a new power transistor. (A771).
Amazingly that's all that I could find as faulty!

There's 2 service manuals on hifiengine and the second one down the list from mgcoupe matches the innards of mine, unlike the "L service manual" (third manual on the list).

Now, the original service manual (page 10) .... I followed. - I checked the original "good" channel with these instructions and my meter is reading around the 22mV area in witch the manual states.... thus, I carried on to set the newly repaired channel to the 22mV mark.

Now the weird part... there is a service bulletin (last on the list at hifi engine) shows the test point(s) to be across the emitter resistor. (my reading currently slowly rises to around 10.6mV after a few minutes).

The main question is: should I trust the connection / readings from the bulletin or stick with the original test points from the service manual?

I'd be grateful if somebody could have a look at hifi engine for the documents, I tried to upload them here but the files are too large apparently.

Thanks in advanced. :)
 
Perhaps your 22mv test point is across 2 emitter resistors. And the SB is across only a single emitter resistor.(10.6mv). So ideally its looking for 11 mv across each of the emitter resistors in that amplifier circuit.
 
Nope.. I'd use the service bulletins test points.But perhaps wait until someone with more experience with these SONY's chimes in. I haven't worked on a STR-V model in years.I think it was a 6 or 7.
A close up clear photo of all of the test point connections (both pos.and neg. test lead connections) in your receiver would be helpful.
 
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Thanks so much for your input avionic!
The service bulletin, attached, shows describes the original and updated way to measure.

....oh, one more question, since the service manual don't mention..... Should I have 8 ohm dummy loads on the speaker outputs while measuring or leave the speaker selector switched off?
 

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  • hfe_sony_str-v3_service_bulletin_105_en.pdf
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Thanks so much for your input avionic!
The service bulletin, attached, shows describes the original and updated way to measure.

....oh, one more question, since the service manual don't mention..... Should I have 8 ohm dummy loads on the speaker outputs while measuring or leave the speaker selector switched off?
I read the SB earlier. It just moves the test point from the collector lead to the emitter lead of the outputs.
 
Which is exactly how I would make the measurement/adjustment. With no source. No load and volume control at min.
 
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