Sony STR-AV950 Display Problem

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

Mark Z.

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.

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.

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

Mark Z.

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).

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

Mark Z,

Here is an excerpt from the service manual:

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.