Water damaged SONY STR-DE875

[Steve]

I have a water damaged SONY five/six channel STR-DE875 receiver that
I'd like to repair. I'm looking for where to get the circuit diagram
(for the whole receiver or the power amp sections) and/or some quick
help on the power amp section.

Resistor R753 has vaporised (heat burn out) and I would like to know
it's original value/function and maybe why it would self-destruct. It
is a part of a power amp that I think is the Sub-woofer driver and the
other 4 amplifiers do not have the circuitry section it sits in. One
power output transistor feeds through this resistor into what looks
like the base of a transistor dealing with power on/DC protection
maybe (very vague here).

The receiver went through a fire (no heat damage) and hosing (water
damage), where water sat on the main power amp board for a week. I'd
really like to resurect this beast.

Thanks,

Steve

 

[James Sweet]

I have a water damaged SONY five/six channel STR-DE875 receiver that
I'd like to repair. I'm looking for where to get the circuit diagram
(for the whole receiver or the power amp sections) and/or some quick
help on the power amp section.

Resistor R753 has vaporised (heat burn out) and I would like to know
it's original value/function and maybe why it would self-destruct. It
is a part of a power amp that I think is the Sub-woofer driver and the
other 4 amplifiers do not have the circuitry section it sits in. One
power output transistor feeds through this resistor into what looks
like the base of a transistor dealing with power on/DC protection
maybe (very vague here).

The receiver went through a fire (no heat damage) and hosing (water
damage), where water sat on the main power amp board for a week. I'd
really like to resurect this beast.

This could end up being a monumental task, it's really hard to say what was
damaged, you could be lucky though. Chances are a transistor has shorted if
the resistor has burned up.

 

[John]

I have the circuit for that amp on a but from memory its about 15MB. I will
probably have to snail mail it dont think i can send it as an attachment its
too large.

 

[Mark D. Zacharias]

That is given as a 1 kohm 1/4 watt carbon resistor.

Mark Z.

 

[Steve]

This could end up being a monumental task, it's really hard to say what was
damaged, you could be lucky though. Chances are a transistor has shorted if
the resistor has burned up.

I've had very good success at recovering damaged gear in the past.
This one is not for financial considerations, just the joy of fixing
it and listening to the restored product.

The worst bits about water soaked amps to me are

(a) The inter-board connections on those flat push in cables.
(b) Carbon track coated plastic switch contact matrix sheets
(c) The steel screws that rusted and then dribbled down onto
dissimilar metal components (legs usually) which take a little longer
to corrode away even after the water is gone.
(d) Non-responding preprogrammed processor chips that I cannot buy
(e) Storing the bits/boards during a long fix and remembering where
the screws and cables go back into when putting it back together.

I've got a DCamera (with a good macro) lately which helps with that
last one. Dead discretes aren't usually a problem unless in their
destruction, all labeling has disappeared.

Thanks for the response,

Regards,

Steve (In the land of Oz)

 

[Steve]

That is given as a 1 kohm 1/4 watt carbon resistor.

Mark Z.

Thanks Mark,

Is it possible to obtain a small section copy of the circuit around that component?

Regards,

Steve

 

[Mike]

check ur output transistors.

 

[Mark D. Zacharias]

I was never able to find it in the schematic. The rating I gave came from
the parts list.

I have a PDF file about 19 meg. PDF's for the most part cannot be broken
up - they're designed so that only the document creator has this level of
access.

I'd be happy to answer any questions you might have, or if you're able to
take an attachment of that size.....

Mark Z.

 

[Steve]

Thankyou for you're response Mark.

I'd like to get my hand on the whole document (if you don't mind the
19M upload time). If this is acceptable, I will join one of the
on-line file holders which offer around 20Mbyte of disk and let you
know. I also have programs which chop files up into sections for later
re-assembly if you want them.

To get parts of a schematic from a PDF, I usually get the section I
want on the screen and hit "Print Screen" which places the screen
image in the clipboard. If you go into something like paint, you can
paste it back and cut out the bit you want and save it as a gif or
something.

Hope this helps and/or you agree to send it (somehow),

Regards,

Steve (In the land of Oz)