Sony STR-DE335

[PMan976]

I have a Sony STR-DE335 that keeps coming up with "PROTECT"
I checked the center pin on all the Emitter Resistors and they all show a high voltage ( 46vdc ) and I know they should read low-voltage. I have been searching and searching for bad components and I haven't found any yet. I tested all of the output transistors and they all appear fine. Any help with this would be appreciated. I should also add that when I was testing , I accidentally blew the 12v regulator before I discovered that the unit would power up with no " PROTECT " error and all of the voltages on the emitter resistor read low voltage, but I was not getting any audio out. After replacing the 12v Reg, protect came back as well as high voltage.

[R_J]

Re: Sony STR-DE335

When you "blew" the regulator you likely also blew the fuse resistors.

[CapLeaker]

Re: Sony STR-DE335

Usually Sony amps have transistor pairs for each channel. I doubt that all channels are showing bad at the same time usually it is just one. If the output stage and the big resistors are showing good, the problem has to lie before that, like a driver or pre driver ic. I also would take the board out and check for dry solder joints on high heat areas. It may be just as simple as that. Another idea I got is the area of the power amp ic. Hope it helps...

[PMan976]

Re: Sony STR-DE335

Thanks for the input. I tested all of the Transistors and the resistors and they are all within spec. I also went through all of the solder connections to see if there were any cold solder joints, and there weren't any obviously bad ones. I resoldered all of them anyway to be safe. I found it odd as well that all of the resistors show high voltage. I found a service manual for this unit and will dig deeper ( available here if anyone wants a copy- )

[CapLeaker]

Re: Sony STR-DE335

What about the driver ic?

[R_J]

Re: Sony STR-DE335

I found it odd as well that all of the resistors show high voltage.

Do you mean the emitter resistors like R616, R766?
Do you have the B- voltage getting to the outputs, Q604/Q754 should have -39v
You may have checked the output transistors but IC701,IC702 or IC501 may be at fault.

I accidentally blew the 12v regulator

You mean ic801? if yes, did it short to ground or did it short input to output?
Do you now have + and - 12v as well as + and - 5 volts?

[PMan976]

Re: Sony STR-DE335

Do you mean the emitter resistors like R616, R766?
Do you have the B- voltage getting to the outputs, Q604/Q754 should have -39v
You may have checked the output transistors but IC701,IC702 or IC501 may be at fault.
You mean ic801? if yes, did it short to ground or did it short input to output?
Do you now have + and - 12v as well as + and - 5 volts?

Yes, the emitter resistor are R616, R766, and R666 and R716.

I get on Q604
B= -44.7v
C= -76.2v
E= -44.2v

I get on Q754
B= -45.2v
C= -76.4v
E= -44.8v

Q 501,701,702 appear fine.

While checking out the answers to your question, I found I am getting -12v on IC802 but not getting my +12v on IC801, and my 5v line is only 2v but as it is fed by my +12v it is to be expected. I am not getting my B+( 18.1v)for my +12v Regulator. I will take some time and see why.

[R_J]

Re: Sony STR-DE335

Goto #2 (R810,R811)
Having -45v on the output base's could indicate a bad ic (such as ic701 or ic 702)

[PMan976]

Re: Sony STR-DE335

Goto #2 (R810,R811)
Having -45v on the output base's could indicate a bad ic (such as ic701 or ic 702)

I found the 12v regulator problem, I found that I forgot to reconnect one connector CN5702 . I now have all my voltages 12v +and - ,5v, are all good now.

I checked IC 701 and 702 and yes it appears bad , I have high voltage on almost all of the pins on both IC's Now I have to get replacements before I can move forward.

[PMan976]

Re: Sony STR-DE335

I found the 12v regulator problem, I found that I forgot to reconnect one connector CN5702 . I now have all my voltages 12v +and - ,5v, are all good now.

I checked IC 701 and 702 and yes it appears bad , I have high voltage on almost all of the pins on both IC's Now I have to get replacements before I can move forward.

I replaced both IC 701 and 702 and still the same. It might be going to the trash heap soon.

[CapLeaker]

Re: Sony STR-DE335

You forgot to check another driver. IC501. We don’t know which channel is blown. Look at the pdf page 13 / 14 block diagram. You have to figure which channel is blown.