Peavey C30: noise forever ?

[ricci]

Hi guys,
to reduce the hum I shielded my strat (guitarnut docet) but I have not solved anything. The power transformer of the C30 is still very noisy when playing the single coil even at 2 meters away. Anyone has solved the problem of hum ( transformer replacing? ) or there is no hope?

Have a good time

[Don Moose]

How good is your guitar cable?
How secure is the C30's input jack's ground connection?

[ricci]

I use original fender cable and the input jack's ground connection it's ok.
When I play in small pubs, I am forced to stay close to my C30 and the problem is annoying when I use the crunch channel or a overdrive pedal in the clean channel with master volume at about 6 / 12. But it seemed to me a common problem in all C30.Anyway,mine is an old release.
Do you say that those built now do not have this problem?
(sorry for my english)

[cminor9]

what makes you think it's the power transformer?

has it always been noisy? Did it just start?

What happens when the amp is on but no guitar or guitar cable is plugged in? Is it still noisy? Does the hum get louder with your guitar's volume knob? Is it only noisy when plugged into certain outlets?

This kind of info is good to know if you're troubleshooting hum.

[ricci]

what makes you think it's the power transformer?

has it always been noisy? Did it just start?

Yes,always noisy.
With no guitar and cable plugged,I just hear a light hum constant and increasing the volume i hear to increase just the hiss.
The annoying hum occurs only with the crunch "channel" or with an overdrive (plexitone) in the clean channel and obviously this hum increases in proportion to the volume and proximity to the power transformer.I thought that the transformer was not well shielded(laminations?) and its magnetic field to interfere (rightly so) but too much with that of the single coil.
Possible ?

thanks!

[cminor9]

Yes,always noisy.
With no guitar and cable plugged,I just hear a light hum constant and increasing the volume i hear to increase just the hiss.
The annoying hum occurs only with the crunch "channel" or with an overdrive (plexitone) in the clean channel and obviously this hum increases in proportion to the volume and proximity to the power transformer.I thought that the transformer was not well shielded(laminations?) and its magnetic field to interfere (rightly so) but too much with that of the single coil.
Possible ?

thanks!

Here's what I would do. Follow the process of elimination in the signal chain. Plug your guitar and cable into a different amp. Plug a different guitar and cable into your amp. That'll tell you pretty quickly where the hum is coming from. Also, pay attention to which knob make more hum. If turning up the guitar increases the hum, then it's your guitar, for example. If it's your guitar, then play a guitar with humbuckers. It might be just good old fashioned 60 cycle hum, which single coil pickups naturally generate.

If you find it's the amp that's hummy, then try different tubes. Then, if it's getting old (>10 years) it might be a good idea to think about changing the filter caps.

In my experience, higher gain amps will generally be noisier (save for some top end ones, which I think you know will not have a Crate or Peavey nameplate on them.) Since there is more gain going, that means there is more amplification of the original signal happening. So even a small amount of hum will get louder when you crank up the gain. I'd concentrate on the clean channel for now, since I am assuming you get the hum on the clean channel too.

Bottom line, try the process of elimination on simple things before you jump and replace the power transformer. That's a somewhat expensive surgery, and probably not necessary.

Hope that helps.

[ricci]

I have already done all the tests that you said
It remains only the polarized capacitors that are located after the bridge of the Graetz (?).

Indeed,one year ago I was thinking of replacing all polarized capacitors beginning with those larger and I had begun to replace C45 and C46 but I have not had time or desire to continue.


Or will it be the fault of my drummer that forces me to play full

[cminor9]

I have already done all the tests that you said
It remains only the polarized capacitors that are located after the bridge of the Graetz (?).

Indeed,one year ago I was thinking of replacing all polarized capacitors beginning with those larger and I had begun to replace C45 and C46 but I have not had time or desire to continue.


Or will it be the fault of my drummer that forces me to play full

So then it sounds like you are sure it's the amp. One rule of thumb that I read here once is that hum is occurring before the knob that affects it. So I'd try twiddling the knobs on the amp to pinpoint the problem. Filter caps are certainly suspect if they are relatively old.

Might be a good idea to search this forum for similar issues too, or search the net to see if others complain about the same amp being noisy. Even though changing filter caps isn't the most difficult thing in the world, any unnecessary repair is a WOMBAT (Waste Of Money, Brains, And Time). Know that it can be dangerous to mess with filter caps (or anything in the amp) if you don't know how to discharge the filter caps. Depending on the layout of your amp, they could be tricky to get to. And of course, if they are mounted to a PC board it can be tricky to remove them without damaging the board. Not sure how experienced you are with soldering or amp repair, so forgive me if I am telling you stuff you know already.

Hope you get it worked out though. If you have tried swapping guitars, etc, and have determined that your amp is the problem, and new tubes didn't help, it just might be time to think about the caps.

And yes, tell your drummer to quiet down If your playing small pubs and so on, there is no reason to run a 30 watt amp full out! I have a hard time making my 15 watt amp quiet enough!

ooh, just noticed that you said you were replacing caps with larger values? Don't do that unless you know exactly what you are doing! Just replace with something as close as you can find in terms of capacitance and voltage. And you shouldn't have to completely recap the whole amp. Just the filter caps, the big ones with high voltage ratings (400-600vdc) and high capacitance ratings (22uF, 40uF, 100uF, or whatever they are)

[ricci]

I'm trying to search,although apparently this is a problem common to all owners of this amp.
Thank you again for your suggestions.

[bluesfreak]

I had some C30 which did have issues with hum but mainly this was caused by the Power Tranny itself (screws loose!). Did you check C44 on the bias supply ? The problem is that the caps do suffer from the heat (cheap chinese crap) so I would replace C39-C46, balance the heaters using 2x100 Ohm and replace the whimpy OT with the Marshall DSL 401 type.

[ricci]

Hi,Blusfreak

Unfortunately i had already checked and the screws were tight enough.
I will try to replace the caps.

[Enzo]

If your guitar pickups are picking up the magnetic field from the power transformer, that is not something "wrong" with the amplifier.

[ricci]

Hi Enzo,glad to hear you after so long
My strat is shielded but probably I demand too much from the single coil.

best regards

[Gtr_tech]

Single coils pick up hum....thats just the way it is. The loudness of the hum is relative to how much preamp gain is used and the guitar's proximity to the amp or anything else that radiates EMI. You may need to go to a hum cancelling type like a Dimarzio HS3 or similar.

Try a different guitar with humbucking pickps. Problem gone/lessened? There you go....

[ricci]

Try a different guitar with humbucking pickps. Problem gone/lessened? There you go....

I do not need to try a guitar with humbucking because in position 2 (bridge + middle) and 4 (middle + neck) the noise disappears. So I think it is an inherent problem of single coil and I can also understand it !!
But when i am forced to play close to the amp is a disgrace and then becomes a frustration.