yamaha av receiver repair

[kelvin marsden]

yamaha rxv673 won't power up. self diagnostics indicate power transistors problem "Iprt". removed power transistors and tested on 15 dollar tester. all transistors test as diodes. i don't know what that means. does that mean all transistors are shorted? what could cause all the power transistors to shrort.
any help would be appreciated.

 

[Nigel Goodwin]

I can't see anything in the service manual about self diagnostics checking power transistors?, or any mention of 'lprt'?. I'm dubious about any such function?.

Transistor amplifiers are like rows of dominoes, anything fails and the output stage is catastrophically destroyed. This isn't a gentle occurrence, burnt components and fuses blown to bits are highly likely.

I'm also a bit concerned about randomly removing all the output transistors, the chances of much greater damage have become vastly greater.

Even assuming some output transistors have failed, it would almost certainly only be one channel - and you shouldn't touch any other channels.

What was the exact self diagnostic function that caused you to remove the transistors?.

 

[ahsrabrifat]

Test between Base and Emitter, Base and Collector, Collector and EmitterFor BJTs, you should see diode-like readings from base to emitter/collector but open circuit in reverse polarity. Any low-resistance reading across collector-emitter is a clear sign of a short.