Loud Buzz from Marshall Valvestate 65 (solid state)

[markh99999]

So, it sounds the way a bad chord sounds when plugged into a guitar, only the sound is not from the chord or guitar, I know this much. At any volume, even when volume is cut completely, the buzz is there; in fact the volume knob barely affects the buzzing sound. Sometimes it won't be there at all upon turning on the amp (though it usually is), but then vibration or even a slight bump could start it up again.
I discovered that if I smack the top of it when it's buzzing, it goes away temporarily, but then playing makes it come right back. This has me wondering if it's just something a little loose in the left side of the amp. I opened it up and looked without touching anything (for fear of screwing something else) and couldn't see anything that was obviously loose.
Howver, since the problem can't be too serious, because it sounds perfect at low non-vibrating volumes when the buzz isn't present, I'm notgoing to spend a whole lot of money repairing a mediocre amplifier. If anyone can help... please...

[Enzo]

Resolder the main filter caps.

[markh99999]

OK...

OK... So 'm going to resolder the main filter caps. Now where are they inside and how would I go about doing that? I'm not completely clueless; I understand what solder means.

[Amp Kat]

You may want to send it to a tech as you can create other problems on the PCB if your not extremely careful. Your going to have to pull the main board as the solder joints are on the bottom side. Mainly C-11 and C-12 but I would visually inspect all of the capacitors and power resistors and R-41. Any ground connection that is loose could cause this and even an input jack that came loose from moving the 1/4" phono plug back and forth too much or if it fell with the cord plugged in could cause it.

[markh99999]

On the right track...

So, I did exactly what you both said. Before I soldered it, I held the loose one in place and tried playing - it was perfect. So I know that this one loose thing is the problem. I soldered it as best as I could and it felt tight, but when I went to play, it was as it was. Is there some trick to soldering correctly?

[Amp Kat]

What it sounds like is that the pad broke away from the trace. If you take a razor knife and scrape away the polyurathane and green covering, underneath that is the copper trace. You may have to take a piece of short wire and bridge them together(solder) to complete the contact. After your done if you have a meter you can check contunuity to make sure it is connected.

[markh99999]

Thanks...

Thank you for your help, but I broke the capicator. Anyone know where I can find a Samwha 2200uF 50 volt capicator (K3A)?????

[Amp Kat]

It doesn't have to be a Samwha just a 2200uf 50V Radial. Try Mouser at 1-800-346-6873 and tell the you need part# 140-XRL50V2200-RC and your good.

[Enzo]

If one of the legs came off, that was probably what was wrong all along, and that is why resoldering the broken leg didn't help. DOnt feel bad.

To replace the cap it is EXTREMELY important you don't put the cap in backwards. Each cap udentifies polarity, usually with a wide stripe down one side with "-" (minus sign) inside the stripe. That means the leg on that side - or closest to it, is the - one, while the other is the + one. The pc board should be silk screened on top with a + near one side.

As KB said, any 2200 cap will work 50 volts. 63 volt caps will work just as well if you don't find 50v.

[markh99999]

Thank you very much

I really appreciate the help you gave me; if I can order the part and put this in working order, I will have saved a lot of money thanks to you. So, thanks.