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Topic:
SONY Receiver STR-DB930 enters Protect mode once powerd on
This thread has 2 replies. Displaying all posts.
Post 1 made on Saturday February 5, 2011 at 19:57
victorshih
Lurking Member
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February 2011
1
My SONY receiver enters PROTECT mode once powered on. It happens without any speaker cable plugged in. I opened the chasis to check on the power transistor using the DMM diode mode and across base & emitter (Vbe) and base & collector (Vbc) there was correct reading of diode voltage drop of about 0.7 V.

Any suggestion what next step I should take? Thanks in advance!
Post 2 made on Sunday February 6, 2011 at 08:23
Daniel Tonks
Wrangler of Remotes
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October 1998
28,779
If not the obvious (such as stray speaker wire strands), I think the next fault is usually the power supply. Had this happen a couple years ago to a STR-GA8ES, unfortunantly it wasn't worth repairing.
Post 3 made on Thursday February 10, 2011 at 00:57
Ernie Bornn-Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
30,104
Yes, there are a lot of things that can go wrong, many more than just the Vbe of one output transistor.

If that unit actually uses discrete output transistors, there'd have to be at least two per channel. If it uses a power IC, measurements would be more involved and you'd need a service manual to locate the problem. Even then, you might locate what you think is the problem, only to find after replacing a part that it's a symptom and the problem remains.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw


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