Pioneer VSX520 No power

[smk279]

I trash picked this receiver and it has no power It's very dusty inside I took out the power board How can I find out what's wrong with it? I notice when I plugged it into the wall or when I press the power button there's no click It only has one fuse it shows continuity

[wasedadoc]

I put 'Pioneer vsx520 service manual' into Google and the first hit was to a free download.  Did you not do the same?

[Zucca]

I would check with a DMM is the main voltage arrive to the board.
If you are lucky it is just a bad mains cable.

Please be careful mains voltage can kill you.

[smk279]

Yes I downloaded it yesterday

[Jeff eelcr]

How would you know if something was burnt open, not by looking, clean it first.
Jeff

[smk279]

I found this av receiver had modular design so I took the whole thing apart, I even removed the power transformer from the chassis Can I plug the power board into the transformer and plug it in without connecting the amplifier board so I can see if the relay clicks when I plug it in, although I don't know if it's supposed to It would surely be supposed to click when I press the power button which I could also connect

[smk279]

Yes, I have to check resistors at their bases because above that the leads are brown rust color and I don't get any reading at all Testing them at their clean bases where they haven't oxidized with my DMM set to beep for continuity some of them show readings ranging from 600 to 1900 instead of beeping

[Jeff eelcr]

I am guessing you do not have a variac, plug and pray is not a good troubleshooting method.
The service manual was a good start, next a good visual inspection then what voltages are there and which voltages are not?
These are the ones that have to be there before power up that I am refering to.
Is the relay good? Is its drive circuit good?
Take your time, be careful, get more experiance, check grounds, check current draw of unit.
Jeff

[smk279]

Thanks but why do some of the resistors show a reading instead of causing the DMM to beep?

[Jeff eelcr]

The beep is for (shorts) a direct connection not to gage resistors.
Higher value resistors will not beep low value ones will.
Jeff

[FIXITNOW2003]

Have you done the reset on page 47 ?
to clear errors summery as bellow

If the unit is automatically shut off after a DC error is detected, no key input will be accepted afterward.(The power will not be turned ON.)Simultaneously holding the [ADVANCED SURROUND] and [STANDBY/ON] keys on the front panel pressed for 2 seconds will cancel Key Input Inhibition mode after a DC error detection and turn the unit ON.

[smk279]

I already took the whole thing apart

[smk279]

I think it's too late for me to try that with the entire unit disassembled

[smk279]

The transistor in the center of the photo is shorted and so is the brown metal oxide capacitor showing above it How do I change them do I have to bend all of the leads on all the transistors cause I'll be bending the board so I don't have to unscrew all of the transistors Is that the way to do it?

[wasedadoc]

No, that is not how you do it!

Give it a proper clean up.  It looks like the transistor leads are soldered at the board edge and you can desolder each lead of that transistor one lead at a time and bend them slightly away from the board.  There appears to be an hole in the board for screwdriver access to remove the transistor from the heatsink.

It is very unlikely that the ceramic capacitor is shorted.  Probably it is across a junction of the shorted transistor.

If you do have to remove the board, free all the transistor leads as above and leave them mounted on the heatsink.

To be brutally frank, you have not yet instilled any confidence in me that you have sufficient competence to bring this attempted repair to a successful conclusion

[smk279]

Do I need to put fresh heatsink plaster when I put the new transistor on? I'll have to order it cause I don't have any

[wasedadoc]

It is not "plaster".  It is called heatsink paste or heatsink compound.  You should remove the remains from the heatsink and apply a small amount forming a thin layer over all the metal back of the new transistor.

When you have removed the old transistor, check if the capacitor still appears shorted.

[smk279]

I removed the transistor and the ceramic capacitor no longer shows a short

[smk279]

Is it different from the stuff used for computer CPU's

[wasedadoc]

Is it different from the stuff used for computer CPU's

No.