Peavey 5150 problems!

[spiderman2812]

I have a 5150 head that had beer spilled in it. The problem is that it blew one of the 6l6 tubes in it and also blew the 2a fuse that controls the stand by cicuit . When i replaced the standby fuse(2a) and plugged it in to check it the main 5a fuse blew immediately. I'm goin to take the boards out this morning to check them and their components and also see if i can get some voltages on the transformer. Has anyone ever had this experience with one of these if so i could use a little advice. Thanks Kevin

[Enzo]

Unfortunately your question sorta assumes that beer spilling inside an amp will somehow do predictable standard things. It won't.

If there is still beer hiding under parts, use plain warm water and a Q-tip to wipe it away. Water will evaporate clean, beer leaves a residue with plenty of crap to carbonize and cause arcs.

Once teh wet is clean, we have to make sure it is dry. If an arc has already formed, it may have ruined the socket or whereever tthe arc was. Make absolutely sure there is not a little bead of water under a part somewhere. A heat gun or hair dryer might help.

[spiderman2812]

Hey thanks . Do you know of any way to get the power board out aside from desoldering the sockets cuz it seems to be rivited in place. I'll probably have to desolder it though. Also i took some readings on the load side of the 2a fuse circuit. The pre amp drawing shows on j72 and j79 the 220k resistors between both sets of capacitors were getting declining readings meaning it would start out at 220k and slowly decline below 160k and kept falling. would it be possible that the resistors are fried cuz i've never seen a resistor do that before. The diodes and caps seem to check out per schematic though. do you think it would be worth replacing the 220 k resistors and possibly one trannie that seemed to feed off the diodes too? Thanks alot Enzo! Oh the link to the schematic is http://www.blueguitar.org/new/schem/peavey/5150evh.pdf

[Keystring]

If you're popping the 5amp main fuse immediately, then I would suspect you have blown diode in the rectifier circuit.

Happened on my Fender Twin. For the exact same reason.

[spiderman2812]

would you suspect it's in the circuit off of j72 and j79? they all seemed to test good?

[Keystring]

would you suspect it's in the circuit off of j72 and j79? they all seemed to test good?

Did you test cr8 cr9 cr10 and cr11 which is the full bridge rectifier?

You need to lift one end of each diode and test individually. I'm not familar with the circuit components so I am assuming they are 'discreet' and not a rectifier 'block'.


That's where my problem was.

Another thing you could try is to 'break' the connect from the rectifier going to the first filter cap c34 and then apply power. If the fuse doesn't blow, then check the voltage from the rectifier.
It will read a little higher than normal but should still tell you if that part of the circuit is ok.

If that checks out then pull the power tubes and power the amp up again. If no fuses blow, then suspect a shorted screen resistor. If not then you need to look at the caps in the power supply section for a short.

If you can isolate each supply section (Plate ,screen and bias) then you should be able to narrow it down a little better.

I have a Peavey VTM 60 and the only way I'm able to do that is pull components (resistor,cap) etc.. to remove the voltage from the circuit.

It can be a pain, but it's generally the only way to know for sure which section is bad.

[spiderman2812]

I didn't lift one end of each diode but i'll give it a shot. The only bummer is that i have it all tore apart and i'll have to put it back together with c 34 lifted to check it out. I'm hoping it's just one of those diodes. That's kind of where i suspect the problem to be. Also Theres a trannie off of one of the diodes in the rectifier set do you think it could have gotten sizzled i think just the collector or emmitter is hooked to the rectifier circuit though. Thanks alot for your help!!

[Keystring]

I didn't lift one end of each diode but i'll give it a shot. The only bummer is that i have it all tore apart and i'll have to put it back together with c 34 lifted to check it out. I'm hoping it's just one of those diodes. That's kind of where i suspect the problem to be. Also Theres a trannie off of one of the diodes in the rectifier set do you think it could have gotten sizzled i think just the collector or emmitter is hooked to the rectifier circuit though. Thanks alot for your help!!

Once you've check the diodes and ruled them out as the problem, then I would test the transformer for a short. If you don't find a shorted winding then put the diodes back in and see what you get for voltage and then go from there.

I know trouble shooting can be are real PITA.

Good luck.

[spiderman2812]

Thanks a million!!

[Enzo]

There are only 8 rivets, drill them out with a 1/8" drill bit. Then when it is time to reassemble it, you install 8 new pop rivets with a pop rivet gun. They are not expensive and rivets are cheap, and they are handy for a number of purposes anyway. Time your shop had one. Unsoldering all those socket legs is silly and impossible to get them all back in the holes afterwards.

Resistors in a circuit that clowly drop in resistance are fine, the current from your meter is slowly charging a cap somewhere in the circuit.

To test the four diodes, just lift the 2A fuse, F1. Now measyre across each of the four diodes. Unless C32 is shorted, eacg diode should be testable in curcuit.

Try powering up with the power tube board disconnected. Pull the ribbon. If it no longer blows fuses, the trouble must be on that board or the OT. Frankly, the OT shouldn't have been under any stress. The primary already has the 500 volts on it. If beer shorts the B+ to ground somewhere, all it will do is remove it from the tranny. Unless the beer got up into the tranny. Not likely with the holes pointing down.

FOr that matter with the tube board connected, pull the three wire conector on the end of the board. That disconnects the OT only.

If you want to test the power tranny, then lift all four inner fuses from their clips. Leave the mains fuse in of course. Now power up the amp. If the mains fuse holds, the tranny is OK.

In the center of the power tube board are two diodes. Make sure neither is shorted. A simple way is to remove all power from the amp. And with everything connected, measure resistance to groind from each power tube socket pin 3. None should be conected to ground. Or from the inside, at the end of the power tube board is the three wires to the OT. Make sure neother the blue or brown wire is shorted to ground.

[Rick Erickson]

it seems to be rivited in place.

Another brilliant move by Peavey - not that they have the market cornered on that kind of thing, but service-ability does not seem to be one of their major concerns.

RE

[Enzo]

Actually I think PV stuff is very servicable. We can look at the nightmare inside the Classic 30, but they only made two models that way. The rest are laid out like everyone else's.

As to the 5150, how often do the power tube sockets have to come out. I can drill out the rivets in a couple minutes and reinstall them in less time. On the occasion I have to replace a screen resistor, I unsolder it on the solder side facing me, poke it out through the holes and let it fall in, where I remove it with needle nose, then I solder the new resistor ON TOP on the foil side. Neat as can be. Other than those resistors, work on that board is rare.

Lining up a 5150 next to a TSL100 and assigning me to demount and reinstall the power tube sockets, believe me I'll take the 8 rivets and a board right in front of my face over the Marshall spaghetti mess any day.