peavey 6505+ repair need some help

[nonoxxx]

Hello,

I am a little noob concerning tube amps, I am more used to build/modify/repair pedals .

I recently got a free 6505+ Combo that I am trying to fix .
I don't know what really happens cause I don't know the previous owner , but some components were fried
https://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-6505PLUS-112-Schematic.pdf

I replaced the big filter cap ( C32 /C33) , R17 ( the value was 470 instead of 390 Ohms) , I replaced R102/R103
and one of the diode bridge rectifier ( D19,D18,D23,D24).
And also C83 looked damaged -> replaced .

After I tested all the components of the supply stages with a multimeter.

I probably made a noob error, for testing it : I powered the amp whithout tubes, I put the standby on and C33 Fried :)

I would like to know what is the best way for testing it ? and to be sure that nothing will fry again before powering it

Thanks,

[shooter]

 

welcome to the results of things gone bad!
somehow Peavey was able to engineer catastrophic into most fails 
all the repairs I've done have had fried boards n parts.

you have to start with a solid PS, you have to know "how to do that" unloaded AND loaded.  Then add 1 circuit, test, add a 2nd circuit........

and C33 Fried

only way I see from quick look, it was bad, it was wrong VDC value, or it was backward
OR you fed it AC from a rectifier that should be feeding DC

If all that makes sense you have a start, if it don't, you might want to sneak up slowly with a small build to "understand" the normal operations and how each circuit works

[sluckey]

R17 ( the value was 470 instead of 390 Ohms)

Schematic shows R17 to be 470Ω. But R17 is connected to the return jack. It's unlikely that R17 will ever fail. Did you perhaps mean R7?

C33 Fried

Most likely cause would be you installed it backwards.

Why did you replace D19,D18,D23,D24? Were the little tubes not lit up?

You're gonna have to divide and conquer. Evaluate one part of the power supply at a time. Gonna have to measure some voltages.

[shooter]

It's unlikely that R17 will ever fail.

It's amazing what a musician can do
did a repair where they plugged speaker out of one amp to Fx return of another amp 
I charged extra 

[nonoxxx]

Sorry it was the big resistor r7 no r17
The cap was not backward ,
For my test I powered the amp without any tubes and the cap  c33 fried when pushing the standby on

[nonoxxx]

Skuckey : I changed the 1n4003 because there was some trace of burning ,and I had domes 4003 laying around :)

[sluckey]

The cap was not backward ,

OK, next step... Leave the standby switch off (open contacts). Turn on the power and measure the B+ voltage across C32. What have you?

[nonoxxx]

I will check it in one or two hours it.s time for dinner in France and I have to put the childs to sleep lol I will measure it after
Thanks a lot for your help :)

[nonoxxx]

So I tested it and strangely , now the new cap is working fine (no burning ) while putting standby on.
I checked the voltage without any tubes installed I got something like  230 volts at pin 3 and 4 on each 6l6 sockets . (no tubes installed)

[silverfox]

Did you check the D25-D28? Those are, I believe, snubbers for HV transient spikes. It seems to me also in the past, I found the Anode pin on the output tube of a Peavey had arced and burnt the tube socket. It also in the process leaves a carbon track that easily shorts even if the tube is replaced. If it did arc, you should just replace the tube socket.


edit- RE pins 3-4: That is very low as I recall. Should be over 425 volts DC.


silverfox.

[shooter]

230 volts

agree that's pretty low unloaded

what do you read vdc across C24 ?
go back and measure VAC across C33?

have you looked at the bottom of the PCB?  that's where I typically find even more fun with Peavey 

[nonoxxx]

I made an error , after checking correctly , its 530 volts so all seem fine
Thanks for the help,but  I still don't know why the first cap I installed died ...

[shooter]

530 volts

I still don't know why the first cap I installed died

what was it's vdc rating?

you still need to check bias vdc for power tubes.
I would make sure all the voltages are good, like filament string, lo volts DC etc.

[nonoxxx]

Yes I will do that this week ,
The vdc voltage of the cap ils 550v like on the schematic , perhaps this one was a bad one , to short for running the amp without tubes ,It.s a mistery :)