Sony STR-AV950 Display Problem

[MrTobor]

I have a Sony STR-AV950 receiver which works fine except that the
display does not light up. It lit up intermittently for a while
(sometimes when receiver was hit). Now it will not come on at all.

Any ideas? TIA

 

[Mark D. Zacharias]

I have a Sony STR-AV950 receiver which works fine except that the
display does not light up. It lit up intermittently for a while
(sometimes when receiver was hit). Now it will not come on at all.

Any ideas? TIA

Solder connections along the FL tube itself, solder connections at the -30
volt source, could be the -30 volt regulator transistor bad.

Mark Z.

 

[UCLAN]

I have a Sony STR-AV950 receiver which works fine except that the
display does not light up. It lit up intermittently for a while
(sometimes when receiver was hit). Now it will not come on at all.

Any ideas? TIA

Mine was doing the same thing. THREE TIMES I opened it up to troubleshoot,
and each time the problem would not occur when the unit was opened up. I
finally just resoldered a bunch of connections. It lit up fine for a few
weeks, then went intermittent again, then returned to its "always dark"
state.

I said "screw it", and bought one of the ES series receivers with the
switching amp. Sold the STR-AV950 to someone who didn't care.

It was otherwise a great receiver.

 

[none]

Mine was doing the same thing. THREE TIMES I opened it up to troubleshoot,
and each time the problem would not occur when the unit was opened up. I
finally just resoldered a bunch of connections. It lit up fine for a few
weeks, then went intermittent again, then returned to its "always dark"
state.

I said "screw it", and bought one of the ES series receivers with the
switching amp. Sold the STR-AV950 to someone who didn't care.

It was otherwise a great receiver.

Most of these displays have a small bulb as the backlight. A bad
bulb can occasionally have the filament make contact when it is
thumped. Replacing the bulb with an led (make sure it has a wide
beam) will mean it only needs to be fixed once.

 

[MrTobor]

Thanx all

You're right, UCLAN it is a great receiver -- ahead of it's time
feature-wise. I'd hate to get rid of just for that reason.

The backlight in this case is a fluorescent tube. I might try
replacing it as a last resort to dumping the receiver.

 

[Mark D. Zacharias]

Most of these displays have a small bulb as the backlight. A bad
bulb can occasionally have the filament make contact when it is
thumped. Replacing the bulb with an led (make sure it has a wide
beam) will mean it only needs to be fixed once.

I'd be pretty surprised if this used a lamp.

Mark Z.

 

[Mark D. Zacharias]

Thanx all

You're right, UCLAN it is a great receiver -- ahead of it's time
feature-wise. I'd hate to get rid of just for that reason.

The backlight in this case is a fluorescent tube. I might try
replacing it as a last resort to dumping the receiver.

The FL tube itself is not your fault. There is a circuit problem. It can be
fixed, I would think - but a service manual will probably be required. They
can usually be had in downloadable form for around 15.00. Sony doesn't sell
it this way but there are second sources, like servicemanuals.net for
example.

Mark Z.

 

[MrTobor]

The FL tube itself is not your fault. There is a circuit problem. It can be

fixed, I would think - but a service manual will probably be required. They
can usually be had in downloadable form for around 15.00. Sony doesn't sell
it this way but there are second sources, like servicemanuals.net for
example.

Mark Z.

I bought the service manual ($19.95). Unfortunately, I am a layman
with only a basic knowledge of electronic circuitry. (Took an
electronics course at a community college a few years ago).

Solder connections along the FL tube itself, solder connections at the -30
volt source, could be the -30 volt regulator transistor bad.

I'll try to identify the -30 volt regulator transistor and check the
solder points along the FL tube.

 

[MrTobor]

Mark Z,

Here is an excerpt from the service manual:
http://www.luzalasnacionestv.com/images/strav950.gif

It shows the -30V line going into the display board (highlighted).
Which one of those transistors would be the -30V regulator?
Q803 or perhaps Q853? Thanks.

MrTobor

 

[Mark D. Zacharias]

Mark Z,

Here is an excerpt from the service manual:
http://www.luzalasnacionestv.com/images/strav950.gif

It shows the -30V line going into the display board (highlighted).
Which one of those transistors would be the -30V regulator?
Q803 or perhaps Q853? Thanks.

MrTobor

Q853 would be the -30 volt source. The output side is the emitter, shown on
the left side of the 3 connections shown on the transistor in this picture.
Since the problem was intermittent, the likelihood is that either there are
bad solder connections at this transistor, or perhaps the transistor has
developed a bad internal connection. This would usually be a bad
emitter-base junction. Normally one would measure about 0.6 volts across a
good emitter-base junction unless it is reverse biased. If for example you
measured several volts across the E-B junction, and the output at the
emitter is low or missing, then the transistor has failed in this manner.


Mark Z.