Another broken Sony receiver... won't turn on

[rkc7]

Ok.... so I have a Sony receiver. That's the problem right? STR-DE595. Anyway, I purchased it in order to repair and resell, but the problem seems more complicated than anticipated. It won't turn on at all... no protector mode, etc. The power supply fuse isn't blown, all transistors seem good, transformer is putting out voltages that seem correct (when I manually turn on the AC supply relay). So, I plug it in, and press the power button... nothing. I've tried looking at a bunch of different things, and nothing apparent seems wrong. I'm considering removing all of the relays and testing them individually, but my impression is that relays typically don't go bad. Anyway, any help on what could be the problem or what else I should check would be really helpful. Thanks.

[alaskanaudio]

When I was in the repair business I ran into a number of problems like you describe. I’m not familiar with your particular unit but most of the newer equipment such as this is controlled by microprocessor mounted on the front panel circuit board. This processor may not be getting power or is being held in a reset condition. This will cause the symptoms you describe and the receiver remains off. If your unit has such a processor you may need a circuit diagram to help follow the power and reset paths. You could have a failed processor, but it would be wise to check all of its supply and control voltages before replacing it.

[anatech]

Hi rkc7,
It sounds like the AC detect circuit may not be working. Look for a approx. 1 uF capacitor feed by a single diode. These tend to go open and hopefully will be an easy fix.
Like alaskanaudio, I am not familiar with this exact receiver, but the circuits should be common to most, in form. If you have a 'scope, look for a big ripple waveform on a small cap that goes to ground. If you see a half wave rectified waveform, it's open for sure.
-Chris

[tenderland]

Make sure no buttons on the front panel are pushed in
if a switch is activated when powering up micro may not work.
check connectors going to the display board and check for 5 v
check for cracks on display board or main board.


JEFF

[Rimband]

Originally posted by rkc7
Ok.... so I have a Sony receiver. That's the problem right? STR-DE595. Anyway, I purchased it in order to repair and resell, but the problem seems more complicated than anticipated. It won't turn on at all... no protector mode, etc. The power supply fuse isn't blown, all transistors seem good, transformer is putting out voltages that seem correct (when I manually turn on the AC supply relay). So, I plug it in, and press the power button... nothing. I've tried looking at a bunch of different things, and nothing apparent seems wrong. I'm considering removing all of the relays and testing them individually, but my impression is that relays typically don't go bad. Anyway, any help on what could be the problem or what else I should check would be really helpful. Thanks.

Hello rkc7, I have a service manual for that receiver in PDF format, I can upload it to you if needed. It is about 6 MB in size. While you're at it, check the standby transformer, those are known for opening up the primary, which will cause a dead receiver.

If your mailbox can handle a 6MB file, please let me know at rimband@hotmail.com (not my DSL account). I'll E-mail you through my DSL account and upload the manual for you!

Joe

[rkc7]

Wow, thanks for all of the advice. Unfortunately, I don't have a scope, just an advanced multimeter that can measure the normal current, voltage, resistance, etc... with diode check, transistor check, and caps up to 200uf. I would be very happy to receive the service manual. You can send the file to skimaniac3@spymac.com, that should have much more than enough space. I'm going to try looking at everything mentioned, and I'll report back. Thanks!

[rkc7]

Doh! I have a new problem... my receiver isn't STR-DE595. That's what the auction said, that's what the box said, but that's not what the receiver says. It's actually a STR-K502P... a cheaper, older receiver. Anyway, anyone have a service manual for this model?

[rkc7]

OK... I found a service manual and have done some testing. Capacitors I've tested so far have been good. But I tested the standby transformer and here's what I found:

2 pole side: 11ohms between poles
3 pole side:
between 1,3: 900ohm
between 1,2: open
between 2,3: open

Take a look at the diagram. Pole 1 is the bottom, 2 is middle, 3 is top. Thanks.

[anatech]

That in itself is okay. What's the voltage on the secondary?
-Chris

[rkc7]

Attached is a diagram of the measured voltages from the transformer. The bracket that has two voltages were measured with the red lead connected to the pole nearest the voltage.