No sound at all from Peavey 6505 Plus 112 combo

[10mesp]

Hi everybody. This is my first post here and I am pretty inexperienced with tube amp maintenance, so please let me know if you need any additional information.


I have a Peavey 6505 plus 112 combo that I bought used about 6 months ago. There were no issues with the amp according to the previous owner. It has been a great amp and I fell in love with the lead tone, until just recently.


I think I may have left the amplifier on for a few days last week. I'm not 100% sure about that. But there was a big storm the night before I found this problem. I don't think we lost power in the storm, but perhaps there was a quick power surge I didn't notice. The day after the storm, I went to turn the amp on and there was no power whatsoever. I checked the fuse that is accessible in the back of the amplifier and found it was blown. So I replaced it, and now it powers on. However, there is absolutely no sound coming from the amp. No hum, static, nothing. Not even noise from the reverb springs when I shake it lightly.


I have tried different speakers, plugging guitar into the effects return, placing a patch cable from the effects send to return, all with no results. All of the tubes are glowing when turned on.


What are some other things I should check for before taking it into a tech? I am pretty electronics savvy, I just have not really ever had to mess with amplifiers besides replacing tubes.

[Enzo]

OK, th voltages inside can KILL YOU, so be careful.

Check the high voltage fuses inside, OH just check ALL the fuses inside. Outside fuses are ONLY the mains.

Does the green power light come on? And the status (standby) light?

[10mesp]

Thank you. Checking the internal fuses was my next plan. What are the precautions I need to take before checking them? And do I just pull them out to check them like the main fuse?

[Enzo]

You get out your volt meter to determine if 480 volts is sitting in a cap all charged up.

Yes, pull them one at a time, you can't reliably check fuses in their clips.

[10mesp]

So I took the board out to take a peek and noticed the F2 fuse is visibly blackened. Looks like it probably blew. The other fuses are crystal clear.



F2 fuse in bottom right





Whole board


How would I go about draining the voltage? I watched a video that said to connect an alligator cable from pin 1 on the 1st preamp tube to the chassis and wait. However I can't seem to find any pins for the preamp tubes.


EDIT: Nevermind, I found the pre-amp pins. They were smaller than I expected.


Are these fuses able to just be pulled out and plugged in? Or is it something I'd have to solder?

[Enzo]

Those fuses are soldered in, they are called "pigtail" fuses by most techs. I should have recalled they were not clipped in in this model.

High voltage fuses usually blow from bad power tube or tubes. Other reasons are possible though, like shorted rectifier diode or filter cap.

[SoulFetish]

I think Enzo's right about the shorted rectifier. It looks like there is some carbon on the board at the top of the first pic you posted; right in between the 4 diodes and filter caps.

[SoulFetish]

I blew it up the best I could but it looks like there's some burned PCB here I would look into it.
But, like Enzo said please be careful , some of those caps may still have a charge in them

[10mesp]

Thanks for all the replies.

I bought some new fuses today that are the correct ampage and voltage and are fast blow just like the stock fuse, but they are slightly longer than the stock fuses. I guess there is a "short" version that Peavey uses in the amp. Would I still be able to attach this fuse, provided I can get the legs to the soldering points?

And I was successfully able to drain the voltage, so I shouldn't wind up electrocuting myself to death, hopefully! Thanks for the warning though.


I did not even notice the carbon near the diodes. I will check tomorrow to see if it's actually there or just the picture. But I have heard that rectifier diodes go bad in this amp. Would this cause the fuses to blow? And is there any way I can check them with this multimeter?

[SoulFetish]

Thanks for all the replies.

I bought some new fuses today that are the correct ampage and voltage and are fast blow just like the stock fuse, but they are slightly longer than the stock fuses. I guess there is a "short" version that Peavey uses in the amp. Would I still be able to attach this fuse, provided I can get the legs to the soldering points?

And I was successfully able to drain the voltage, so I shouldn't wind up electrocuting myself to death, hopefully! Thanks for the warning though.


I did not even notice the carbon near the diodes. I will check tomorrow to see if it's actually there or just the picture. But I have heard that rectifier diodes go bad in this amp. Would this cause the fuses to blow?

The fuses are probably 2AG type fuses.

[Enzo]

High voltage fuses usually blow from bad power tube or tubes. Other reasons are possible though, like shorted rectifier diode or filter cap.

From post #6

[SoulFetish]

Thanks for all the replies.

I bought some new fuses today that are the correct ampage and voltage and are fast blow just like the stock fuse, but they are slightly longer than the stock fuses. I guess there is a "short" version that Peavey uses in the amp. Would I still be able to attach this fuse, provided I can get the legs to the soldering points?

And I was successfully able to drain the voltage, so I shouldn't wind up electrocuting myself to death, hopefully! Thanks for the warning though.


I did not even notice the carbon near the diodes. I will check tomorrow to see if it's actually there or just the picture. But I have heard that rectifier diodes go bad in this amp. Would this cause the fuses to blow?

Also, the fuse in the bottom right of the first picture(the one that looks cooked), is a time delay fuse it looks like from the label on the board.
You should be able to check the diodes with the diode function on your meter. It's the symbol that looks kind of like an arrowhead on your meter. Make sure you put the leads oriented the right way when you put them across the diodes, or else....

[g1]

Also, the fuse in the bottom right of the first picture(the one that looks cooked), is a time delay fuse it looks like from the label on the board.

Yes. The "T" marked on the board (T1.6AL) means time delay/slow blow.
You need a 5x20mm T1.6A (slow blow) with axial leads (pigtail).
Like this:
http://ca.mouser.com/ProductDetail/B...G3CIp6Mg%3d%3d

[DrGonz78]

[ATTACH=CONFIG]42145[/ATTACH]

I blew it up the best I could but it looks like there's some burned PCB here I would look into it.
But, like Enzo said please be careful , some of those caps may still have a charge in them

Almost appears as if the glue holding the capacitor secure has browned up. I have heard about the glue material possibly becoming conductive, and was wondering if that browning look is a clue to it happening.