Repair of a Sony STR-K900 Receiver: Part 2 

A couple tips on Sony receivers. Output transistor shorting is fairly common, thankfully the protection seems to engage quickly enough to stop additional damage. But be aware that slightly older Sony home theater receivers have a major issue with bad solder joints at the driver ICs due to high temp operation and always need to be reflowed even if the receiver is working. I have a good supply of output darlingtons due to keeping boards from otherwise scrapped Sony receivers. Sometimes they are just beyond repair due to other failures.

Worked on many similar to this. You really need to check the quality of the repaired channel; often there is a burned resistor or two or three, could cause distortion or make it go into protect when the volume is raised. Also if those outputs are counterfeit, they could play for a while and go out. At least check the bias as measured across the pins on the top of the emitter resistors. Compare to the other channels.

I love your videos, great details, thank you so much for sharing.

1:25 “they looked identical to me.” - The number eight (8) on original one has bigger circle on lower half, the spacing between text, edge... the size of the font.

They don't make them like they used to. That's a dinky little transformer for what's supposed to be a 90W x5 amplifier. Though the rating is 90W 0.7 THD which is awfully high. My 24 year old JVC RX701V is 100W/ch 20-20K no more than 0.007. They don't make them like they used to. All that being said, congrats on bringing this unit back to life and keeping it from the landfill!

Hi there, kinda late comment to this video (4 years late) , anyway I own a similar receiver, it's the STR-K1600 which is 6.2 channels (2 subwoofers) and everything is fine with it, no issues at all except for one kinda annoying detail: HDMI input can't handle audio. It's not a flaw, the thing was just designed that way. So if you hook something like an android tv box, the audio signal must get into the receiver through the coax digital input or the optical input. Had to buy an HDMI audio extractor to split audio and video coming from the HDMI source (the android tv box), then connect the HDMI video output of the extractor directly to the tv and the audio (via optical cable) to the STR-K1600. Beside that annoying design everything is fine, works as intended. Very educational video, thanks!

Hi! Thank you very much for this video. My Sony STR-KM3 (Argentina model) is turning off right after power on, displaying a "USB FAIL" error message, despite the model DOES NOT having any USB connector? (I have once repaired the same model, but with USB. The problem was a faulty relay (RY901)). Any suggestion or hint? Thank you.

my receiver stopped giving me sound. what should i do? my optical is working fine

That extra channel could have been a center channel as well

i ask. how to relpeir sonny STR-DK 5? the damage thay have received audio. please i newd the answer. that my ask.

where do you get schemetics from

I have the same receiver, but mine is making a ticking/popping noise like a clock and it's really annoying. any idea what it could be?

Do the numbers 41p or 67 p mean anything?.

Hi man , by making a vidéo people are trying to share their knowledge ; according to me your approches of troubleshooting that device is wrong. The block diagram of power supply is very clear , and by understand it you could fixed your device by explaining it first.