yamaha av receiver repair

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.

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?.

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.

pg 31 of service manual "Display provided when Self-Diagnostic Function started, #2. When the protection function worked to turn off the power." it directs to the P2 protection history. first result was Iprt. I took "prt" to mean protect. the self diagnostic doesn't provide much. "Iprt" indicates the power transistor issue, "current protect". #2-1 says check each transistor before applying power (won't let me do anyway).
unit is dated aug 2013. i bought unit for 10 bucks to try and learn repair. was very clean inside. no sign of any heat damage, no bulge caps, won't power up. little red light blinks a few times when you push power, then shuts down. diagnostics will come on. i've tested a few of the transistors with a multimeter and they test as working. i will test the rest. just the tester i bought indicates they are bad. tester shows them all as diodes. i tested a transistor i removed from something else and it showed as a transistor on the tester?

You need to fault find, randomly checking components isn't how you repair things - with an amplifier the first thing to do is check the voltages on the output transistors - in particular the voltages on the emitters should be very close to zero (within a few 10's of mV). The NPN collectors should be about 60V or 30V (depending on impedance selection), and the PNP's should be -60V or -30V.