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Sony STR-DE915 Needs Repairs

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Jolt

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I need help with a Sony STR-De915 surround sound audio/video reciever.

I get no sound output except the left and right rear surround channels work in surround mode. Im not sure about the center channel cause it only puts out sound in some modes like video/dvd.
I havent tested that.

This is a pretty good reciever and everything seems to work in the display but the A and B main front channel amps seem to be blown. It doesnt give me protect mode in the display or anything just no sound when tested with a good speaker In A,A+B,B and surround or no surround mode.

I look at the boards with the cover off and dont see any problems (only see one fuse near the power supply which looks good) and hear the proper clicks when its switched on or different modes are selected.

The only problem I see is some browning on the upper amp board, near a chip looking element thats not on the heatsink with the FETs, but on the same board. Its a wide black rectangular part with a half circle chip on each side and has about 7 terminals going out into the board right where its browned. This part says NEC uPC 258 1V and 9727B on it and has IC701 on the board near it.

I dont see any smoke or anything just this browness near this part so I think it is what is bad. I think I saw this part is called an output or something like that? Is it an op-amp? Does anyone know what this part is because I can only find an NEC PC258 with 8 or 10 legs and I only see 7 legs on mine from the only angle I can see from with the heatsink mounted.

I was also looking for a place to buy a complete replacement board but the only place I found didnt have the same part number for the board.
The board is the upper amp board with 4 FETs on it that are mounted to the heatsink. There are 6 FETs or so on the lower board but that all looks ok. I think the NEC258 on the upper board where its browned is what is the problem because I think all of the FETs go through it because there isnt one with the FETs on the lower board. ..Is this correct?

The upper board says Sony amp 2F 1-665-778-11 but I cant seem to find these parts in a search. at Parts Solver they had something called a rear amp board complete, but it had a different part number. I didnt see the IC701 part, and the ordering guy there said they didnt find a 1-665-778-11 but he did see a 1-667-775-11 that sounded close to my number but it was called a video board. Would the service manual or parts sheet tell me some different numbers or parts that would make it possible to find a replacement that would work?

What do you think is wrong with this amp? Do you think all of the FETS are bad? I there mabey a bad breaker somewhere because I dont see any fuses. I was hoping to replace the upper board but is there a way I can test the FETs when they're on the board?

Could someone please help? I want to get this fixed but I dont want to spend nearly the cost to buy a new one on service manuals, shipping and parts that I dont need.
Thanks
 

nevada143

New Member
STRDE 915 Sony Receiver

Unfortunately the least of your problems is the fuses for the
DC supplies. They are on the bottom side of the circuit board connected to big iron core transformer. You will probably find one or more open fuses. The chances of the unit needing only the fuses is pretty small. The components that failed caused the fuses to go.

Second...If the rear speakers work as described the top board is fine. The lower board is the front left and right power amp.
Most likely you have lost one or more output mosfets that are heatsinked. When they fail they usually short often taking other compents with them before the fuse opens. I reccommend professional help.
 
Unfortunately as the bloke above me said
Unfortunately the least of your problems is the fuses for the
DC supplies. They are on the bottom side of the circuit board connected to big iron core transformer. You will probably find one or more open fuses. The chances of the unit needing only the fuses is pretty small. The components that failed caused the fuses to go.

Second...If the rear speakers work as described the top board is fine. The lower board is the front left and right power amp.
Most likely you have lost one or more output mosfets that are heatsinked. When they fail they usually short often taking other compents with them before the fuse opens. I reccommend professional help.
:twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted:
 
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