Sony STR-6065 Receiver Left Channel Issues - Page 4 - diyAudio
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Old 18th July 2011, 06:04 PM   #31
Mooly is online now Mooly  United Kingdom
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OK
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Old 18th July 2011, 08:56 PM   #32
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Major setback: Tried to take measurements of Q902 which is on heatsink. As I touched red probe to E, or B don't remember which, I got a spark then my power amp board began to release the magic smoke! No shock or anything; I don't wear jewelry and I never have 2 hands near the chassis LOL!

Sorry to say, that this is just turning into a larger problem the more I mess with it. I'll stick with mono, single ended guitar amp builds I guess. Mooly, thanks for all the help, but with a wife, 2 kids, a huge TO DO list on my home projects, I don't have the time or energy to restore this receiver I bought for 30 bucks on *bay.
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Old 18th July 2011, 09:33 PM   #33
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Last readings on Q902 before frying the power amp:

3v on Emitter
33v on Base
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Old 19th July 2011, 07:17 AM   #34
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That's a shame...
Those readings indicate that Q 902 was duff. When I jumped at the driver being faulty (the high B-E volts) I never thought to ask over the polarity of that reading... I assumed it was Base at 33 rather than the emitter.

tbh it's probably still a worthwhile and fairly easy fix even after what has happened. Output transistors and probably new 0.5 ohms and perhaps a few other minor components that may have been damaged.

Put it on one side and then you can always come back to it
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Old 19th July 2011, 12:37 PM   #35
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Your right . After a good night's sleep, my head's a little clearer and more rational - for the moment. The list for replacement parts in this instance isn't terribly long, so I'll get that going and just take my time. Already found suitable output transistors at Mouser LOL.
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Old 19th July 2011, 11:01 PM   #36
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Just doing a visual inspection the power amp too see where the "magic smoke" came from. Found the culprit right away - resistor R720, a 330 ohm burnt french fry now. After looking it up in the service manual, it appears to be part of the speaker protection circuit.

That's the only obvious burnt component I could find so far. My current to do list is to order this replacement as well as output transistors and some 0.5 5W wirewounds.

We'll see how long my break from this lasts...
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Old 20th July 2011, 07:45 AM   #37
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The speaker protection circuit is highly unusual on this amp... that's worth a discussion in its own right.

If R720 is burnt then there are a couple of possible paths that current could have flowed to cause this...

To rebuild this you need a definite plan to follow and a safe way of powering it all up basically consisting of the bulb tester to limit major current flow and damage.

If it were me I would actually remove for now D704, Q705, Q706 and Q707 as these are in the protection circuit. Test them out of circuit but leave them out for now. The amp will work without these.

Did the outputs Q901 and 902 read faulty doing a simple check with a DVM on "diode" test range.

You need to check all the low value resistors in that area, anything below say 2.2k and to the right of Q703
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Old 24th August 2011, 05:31 PM   #38
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Thats to bad this thread stopped. I was using it to help get my str6065 going...
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Old 26th February 2012, 05:36 AM   #39
KyleM is offline KyleM  Canada
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So to hopefully revive this thread,
does anyone know why 7 of my resistors would burn up on the amplifier side of my sony?

reisistors: R782, R781, R784, R734, R733, R731, R730

i replaced 4 the first time, replaced them and then turned it on and got this surprise.
anyone with some suggestions would be greatly appreciated.
Kyle
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Old 26th February 2012, 07:49 AM   #40
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You are almost certainly looking at failed semiconductors, drivers, outputs and other small signal devices around that area.

This is a complex design that needs a methodical approach to troubleshooting.
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