5150 problem

[BLOODROOT]

need some advice. my 5150 was cutting out in volume. it would go from whatever volume i was at to idle volume. similar to when you are at a bit above zero but can just barely hear the amp. I also had a loud hum. the louder you turned up the amp, the louder the ground hum was. It was not guitar cords, lighting, tubes guitars, speakers or any of that. my Engls work fine as well as all my guitars and cabs.

took the amp apart. all the fuses are ok. no loose wires or anything. I disconnected the footswitch jack from the main board. I heard that was an issue sometimes with this problem. no go.

so after inspection i found that if I pushed on the small brown filter cap that the sound completely cut out. I figured this had to be the problem.

So i ordered another 35 volt 2200 microfarad cap. drained the caps, removed the suspected bad one and replaced it. no go. the odd thing is the new cap was half the physical size of the stock one on the board. also the amp would turn on now. the powertubes light, only one preamp tube lights and none of my leds light up.

so I figured it was due to the cap looking different. so I put the old one back in and still the same thing.

my big question is, all the plugs from the transformer have a plastic end on them and are square on one end and a triangle on the other. they made them plug into the pc board with different parts so you dont plug the wrong one into the wrong plug on the pc board but what if they are turned around the other way. do they all point the same direction or do they go in different directions.

im thinking i have them plugged in incorrectly and the new filter cap may work . but maybe not. thanks for any advice. I hope that is understandable.

Here is a pic i highlighted the plug i was referring to and the original filter cap

[52 Bill]

so after inspection i found that if I pushed on the small brown filter cap that the sound completely cut out. I figured this had to be the problem.

my big question is, all the plugs from the transformer have a plastic end on them and are square on one end and a triangle on the other. they made them plug into the pc board with different parts so you dont plug the wrong one into the wrong plug on the pc board but what if they are turned around the other way. do they all point the same direction or do they go in different directions.

When you pushed on the cap you may have been moving other things on the pc board, causing the sound to cut out. I don't know if the old cap was bad or not, but if you have correctly replaced it, move on and look further for your problem.

I believe that the connectors that you are asking about, are for the ac outputs from the power transformer. Because they are AC they do not need to be polarized and will work in either orientation. Usually when Peavey build these things, the pins themselves are polarized when they have to be and will only fit on in one direction.

[BLOODROOT]

hmmm well at first the amp worked. all the lights and all. it just had to warm up for the sound to not cut off. I replaced the cap. made sure the polarity was correct and that is when the power issue came up. I then put the original cap back and still the power issue. I cant get stuff to power up in order to figure out if it actually needed the cap replaced or not.

[52 Bill]

I cant get stuff to power up in order to figure out if it actually needed the cap replaced or not.

Have you rechecked everything that you did? How about all of those fuses on the board, are they all ok?

[BLOODROOT]

Have you rechecked everything that you did? How about all of those fuses on the board, are they all ok?

yeah they are all good.

[WholeToneMusic]

Try check the Filament wiring for continuity to make sure you have a solid connection. Did you originally unplug the AC you have highlighted in the pic because of the lighting issue?

[drewl]

If it isn't the cap you were pushing on, there's an intermittant pc board connection somewhere.
I've come across this same problem more than once.
Could also be an intermittant ribbon cable between boards.

[BLOODROOT]

Try check the Filament wiring for continuity to make sure you have a solid connection. Did you originally unplug the AC you have highlighted in the pic because of the lighting issue?

i had them unplugged to remove the board. I have a crappy phone cam so I left it unplugged to see the plastic plugs to show what i was describing when asking which way to plug them back in. I have them plugged back in correctly now, someone at another forum took theirs apart and took pics for me. still I get power to the 4 power tubes. but only one preamp tube is lighting up. I tried to plug in the efx return and play and nothing comes out. the leds on the amp dont turn on either. all the the fuses are good. all the ribbon cables are good. its not either transformer either or I wouldnt get power to the power tubes or the one preamp tube. i'll probably take it in somewhere and have them look at it. Im at a loss. thanks for all the comments though guys. I still dont understand it. the amp at least worked before. it just would lose volume from time to time. If i smacked it. it would go back to the correct volume. still had that nasty ground hum. I replaced the filter cap and thats when the problem started so I put the original filter cap back in but it didnt fix the issue. crazy.

[Enzo]

Your preamp tube heaters are stretched between the +24 and hte -24 power supplies. Those are also what runs the LEDs. so I suspect you are missing 0ne of the 24v supplies - or both.

[ahamay79]

Maybe a bad solder joint?