Please excuse me if I'm directing this message to the wrong group. I
have a Sony STR-DE935 surround sound amplifier, and am receiving the
message "Protector" in the disply window when I turn on the power. All
that I can find in the owner's manual is that there is a short
circuit, and the fix is to power down the amp., correct the short
circuit problem, and turn the power back on. I have plugged the amp.
into different wall sockets, and also cleared the memory, but that
doesn't help. Can anyone offer me any advice on how to get the amp.
working again?
Any help would be appreciated, and if I've stumbled into the wrong
group with this question, could any one suggest what group I might
try?
Thanks very much,
Alan

One or both of the output transistors may have gone bad in a channel. I
repaired a Sony receiver for a friend that had two dead shorted output
transistors, a burned resistor and a swollen cap.

John

"Alan R" wrote in message
om...
Please excuse me if I'm directing this message to the wrong group. I
have a Sony STR-DE935 surround sound amplifier, and am receiving the
message "Protector" in the disply window when I turn on the power. All
that I can find in the owner's manual is that there is a short
circuit, and the fix is to power down the amp., correct the short
circuit problem, and turn the power back on. I have plugged the amp.
into different wall sockets, and also cleared the memory, but that
doesn't help. Can anyone offer me any advice on how to get the amp.
working again?
Any help would be appreciated, and if I've stumbled into the wrong
group with this question, could any one suggest what group I might
try?
Thanks very much,
Alan

(Alan R) wrote in
om:

Please excuse me if I'm directing this message to the wrong group. I
have a Sony STR-DE935 surround sound amplifier, and am receiving the
message "Protector" in the disply window when I turn on the power. All
that I can find in the owner's manual is that there is a short
circuit, and the fix is to power down the amp., correct the short
circuit problem, and turn the power back on. I have plugged the amp.
into different wall sockets, and also cleared the memory, but that
doesn't help. Can anyone offer me any advice on how to get the amp.
working again?
Any help would be appreciated, and if I've stumbled into the wrong
group with this question, could any one suggest what group I might
try?
Thanks very much,
Alan

The short they are referring to is a short in the speaker wiring, not the
supply.

r


--
"Any sufficiently advanced technology is indistinguishable from
magic."

Arthur C. Clarke (1917 - ), "Technology and the Future"

Please excuse me if I'm directing this message to the wrong group. I
have a Sony STR-DE935 surround sound amplifier, and am receiving the
message "Protector" in the disply window when I turn on the power. All
that I can find in the owner's manual is that there is a short
circuit, and the fix is to power down the amp., correct the short
circuit problem, and turn the power back on. I have plugged the amp.
into different wall sockets, and also cleared the memory, but that
doesn't help. Can anyone offer me any advice on how to get the amp.
working again?
Any help would be appreciated, and if I've stumbled into the wrong
group with this question, could any one suggest what group I might
try?

This protection is designed to detect a short in a speaker output.
Disconnect all speakers and see if the problem goes away.

If speakers and cables are OK, it may be indicating an internal fault.

I have the same problem with one of my Sony surround receivers. How
the problem occured is a educated guess by me. Here is how I think I
fried the final amp, or something close to it.

I put my surround speakers on A and then some floor standing monsters
on B. I usually use them all for stero music listening, and the las
ttime I used them I was listening to music. I left them all turned
on, both A + B. Next mistake was to have the speaker impedence switch
in 4 ohms, then to amplify the problem to the next level, I put a
surround movie in the DVd the other night. Sound kicked on for a few
seconds, then silence and the smell of smoke. Then Protector flahed
on the receiver screen.

Troubleshooting done so far yielded the fact that I can stop the
protector from kicking on if I pull the power supply leads off of the
final amp board. I can leave every other connector in place, and the
receiver starts up normal, execpt for the one major detail of No
sound.

Next I used my Fluke 87 to check the final transistors while in
circuit in a very rude way. None of them appeared to be shorted, so
all i know now is that I can run the receiver as long as i do not
connect the power supply leads to the final power amplifier board.

I do not think the smell came from that board, and I could not feel
any warm, or hot components with the power on and protector flashing.

The fact that the receiver is somewhat smart and can protect itself,
makes me wonder why the darn thing fried. My guess is that it didn't
have a complete short to react to, but a very low impedence that
caused a part to fry before the protector could stop it, then the
protector saw the fault after it caused a companent to fail, making it
obvious.

I would love a schematic for the DE-835, and a cross for the Sony
parts so I don't have to get them from Sony.

Please respond to my Hotmail, and use Sony in the subject so ican
sort it out from the tons of SPAM that goes there.

Thanks to all that read this and supply a useful comment. Joe

try?

This protection is designed to detect a short in a speaker output.
Disconnect all speakers and see if the problem goes away.

If speakers and cables are OK, it may be indicating an internal fault.

Laurence Payne and all others in this thread:

My long repair experience suggests that the "protection" circuity
actually protects the speaker NOT the amplifier, in most designs.

When the protection circuitry in the amp senses DC on the speaker
rails due to an audio stage component failure, the protection relay
will drop out thus disconnecting and PROTECTING the speakers from the
very damaging DC... usually full power supply B+ voltage and current
which can fry the voice coils in most speakers just about instantly.

Failures in the amplifier circuitry can be easily caused by shorted
speaker wires, running too many speakers, too loud of a volume driving
the amp into severe distortion, other component and circuity failures
due to heat, stressed components, bad solder connections, old age and
just because it was time for a part to fail.

In most designs, an amp will "try" to drive all of it's power into a
short or overload (too many speakers) and will quickly cause component
failures that can not be reset.... the protection circuity will sense
DC on the speaker rails which indicates component and circuitry
failures that must be repaired ..... in most designs it will NOT
sense shorted speaker wires and will not PROTECT the ammplifier.

Best Regards,
Daniel Sofie
Electronics Supply & Repair
------------------



snipped:
Laurence Payne wrote in message

This protection is designed to detect a short in a speaker output.
Disconnect all speakers and see if the problem goes away.

Mark, my parts came today. It took me about 20 minutes and I have my
receiver working with a Dolby Digital DVD with full surround playing
now. Thanks for your help. I replaced the flame proof resistor with a
carbon, but I left it a little off the board. I will be more careful
with the load now that I know how touchy Sony equipment can be.
My Sound Craftsman amp can run down to 2 ohms and deliver about 1000
watts per channel all day long. It is a Class H amp, and built like a
tank.
Total cost to fix the receiver was $9 if you don't count the resistor
I had in my parts bin, and the tools and soldering station I already
owned.
Joe