First of all my STR-DE845 started having the protector problem about 6 months ago and I bought this receiver back in 2001. This is what I found wrong with mine. After searching online I found a service manual for the receiver, this came in handy when diagnosing the problem. The first obvious thing was discoloration of the board around the IC 501, 601, and 701 Op-amps. When looking at the receiver from the front these are the three vertical NEC ICs to the right of the main amplifiers. Even with no load these amps get very warm. Sony failed to add any heat sink to these ICs so eventually they can de-solder themselves, specifically the 701 IC which is the one closest to the back of the unit. With mine I was able to slightly push the 701 more vertical, since it was leaning, and I believe it has helped it make a better contact. The protector circuit will kick in if it senses the Op-amps are shorted or not making contact. The best solution is to add some copper heat sink to these ICs, they already have screw slots for a heat sink. If they ever fail you will have to get new op-amps and re-solder them to the board. Hope this helps.
Thank you for posting this, it solved my problem too! In my case it was IC601 - I just pushed it over a bit and the receiver started working. I'll leave it and see how long it works; if it fails soon I'll remove the main and rear amp boards and re-solder the ICs. I found the service manual athttp://www.epanorama.net/sff/Sony/Audio/...
×
I had a mechanical problem with the relay on the 1st power supply board. The relay right next to the small transformer. The blac cover for the relay just comes right off. Make sure that the little black plastic piece is still in position (you'll see what I mean when you open it.) and check the contacts on the relay.
See my response to kj4bhp above. The service manual is currently available at this link: http://www.epanorama.net/sff/Sony/Audio/STR-DE835,%20DE935.pdf
Determin if the speakers are at fault first. un-hook them and turn on the unit if it stays on one of the speakers is bad. if it remains in protect, the output transistors are shorted. there are a pair for each output. they are located on the large heatsink in the center of the unit.
5 channel suround means 5 output pairs. check for the ones that are shorted, use an ohm meter to test them. only one pair may be at fault, if the over current is detected by the microprocesor the system goes into protection. in other words if there is a short on only one pair, the system detects this as an over current draw and shuts down the ON command. if you use the reciever with only 2 speakers (front left/right) than check those pairs. that at least narrows it down. I'm still tring to fine a link for a service manual for you.
×
Register and download the manual for free at retrevo.com
http://www.retrevo.com/support/Sony-STR-DE945-Receivers-manual/id/387dj982/t/2/
The far left optical connector on the back is an output.
2,102 views
Usually answered in minutes!
could you send me a picture or schematic showing output transistors?
there are 5 ,how could all 5 go out at the same time?
Sony STR-DE845 5.1 Channels Receiver is stuck in protect mode, I found a set of outputs bad and replaced them, prior it would only blow the main output fuses, with no operation. Can I get a skematic of the unit to diagnose further. Can someone get it for me?
×