What do you think is wrong with my amp? Bad buzzing noise...

[spuds]

I've got a silverface fender amp (super six reverb) and its been buzzing badly ever since I've gotten it, and now I wanna solve the problem.

The hum is almost not noticable at low volumes. But if I turn the master volume up past 3 (which I have to) the buzzing becomes obvious - and the more i turn it up, the louder the buzz gets. It buzzes even when my guitar isn't plugged into it... and I noticed it also gets a bit worse when I turn up the treble, or the reverb.

What do you think it is? Transformer? Tubes? Wiring? I haven't retubed it since I've gotten it and so I have no idea how old those tubes are.

I'll definately take it into an amp repair shop but i'm overseas at the moment and would like to know what you guys think it is.

Thanks!

 

[kevlar3000]

Re: What do you think is wrong with my amp? Bad buzzing noise...

Have the filter caps been replaced in the past 20-30 years? A bad tube can do it. I would start with the basic stuff...

Is it the same with different outlets or locations?

 

[shredaholic]

Re: What do you think is wrong with my amp? Bad buzzing noise...

I'd say it's likely to be a bad capacitor leaking DC. It could also be things like a bad tube, or even something wierd like a ground wire that's come loose.

 

[Scott_F]

Re: What do you think is wrong with my amp? Bad buzzing noise...

Listed cheapest to most expensive fix, if you look at Kevlar's thread...

1. Try a different AC outlet, make sure you're not standing too close to the amp with your guitar. Is it on humbuckers as well as single coils? How about with nothing plugged in at all? Still buzz? If so...

2. Find a known good preamp tube and start to replace each tube one at a time, power back up and check for hum. Even though V3 and V6 are normally 12AT7, for this test you can still use the same known good 12AX7 you are using for the other 4 spots. Still buzzing?...

3. Take it to a tech to check for bad caps. Caps are generally thought to only last 10 years or so. When I was overhauling my 68 Pro Reverb, a lot of the caps just crumbled when I touched them. You can take the dog house cap cover off the underside of the chassis. Just lift it straight up and don't touch the cover to any of the filter cap leads (BE CAREFUL). If you see bubbling on the ends of the caps, they gotta get replaced.

 

[ES350]

Re: What do you think is wrong with my amp? Bad buzzing noise...

After all the above, lead dress might be a consideration. The wiring in SF Fenders tended to get pretty sloppy as time went on...

 

[spuds]

Re: What do you think is wrong with my amp? Bad buzzing noise...

Thanks for your help guys.
So it pretty much could be anything...

I've tried it at different locations and it still buzzes. It buzzes the same with or without a guitar plugged into it. I haven't changed anything on the amp since I picked it up about 4 years ago... And it looked like the previous owner didn't really care much for it either.

I guess I'll just have to take it into the shop... but i'll give Scott's preamp tube test first.