No sound output. (1 Viewer)

[Tod Golden]

I have a Sony STR-DE635 receiver that went into protection mode. After cycling power there is no sound output from the speakers. Since it is past the warranty period I took the cover off an noticed two blown 1.5 amp fuses were blown. I replaced these and turned the power on and they blew instantly. Obviously this did not fix the problem and there is something else wrong. I think it may be some sort of output transistor is blown.

My guess is that the cost to repair it is more than the thing is worth. I would like to fix it so I can retire an outdated Kenwood reciver that has been a workhorse for the last 15 years. Does anybody know where I can get my hands on some schematics for this receiver? The receiver is only about 18 months old and I would hate to just toss it.

Tod

 

[Dave Milne]

I assume that you made sure that speaker leads were not shorted when you powered back up.

If so, then you're probably right... blown output transistor(s). Assuming this product uses discrete output transistors, you have likely blown two (both transistors in the push-pull pair). This is a common scenario: one blows (fails shorted)... gobs of DC appear at the output... negative feedback causes the other to drive hard to correct - effectively shorting the supply rails together... the second fails shorted... power supply goes to max current into a dead short... fuses pop.

I'm not sure where to go for a schematic. Sometimes the manufacturer's website has links to schematics for download or purchase.