old fender amp making weird noises

Hi! I forgot to say sorry to everyone, about the fact I did not come here for a long time, but I've been really busy and had internet provider problems too.

Here my problem... Some weeks ago my Fender Bandmaster (blackface, born '64) started makink some noises when idle. They seemed random low-frequency growls, somehow. Anyway, after some time they got more and more loud, and less rare. last time I switched it on, after 20 minutes these noises became continuous and pretty loud too. Swithced it off, to avoid any kind of damage.
Now: I think that the power valves could be dead, at least one of them, even if they did not seem to produce strange colours or else. Has anyone an idea of what it could be? Keep in mind that condensers are still original. I do not know if these noises are due to dead valves, dead condensers, maybe a dead resistor.....
Thanks for your help!

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My money goes on the output valves, whatever you do dont throw away your old ones, they could be a fabled set of Mullards or like.
it would be worth your while getting a new set of matched output valves to see if this is the problem. But in the meantime, I'll hand you over to our in house Valve amp specailist 1bassleft.

Drum roll ............ ... .. .. ... ... .. .. ... ....

Did i give you enough of an introduction bass? i did'nt want to overdo it.

sadly, they're not old cool tubes... just teslas... replaced them a year ago, but got "injured" when the bias resistor (or something like that) got broken...
I'll try to put new ones there then. I'll wait for some advice from 1bassleft anyway...

Best wait for the BASS. What he doesnt know about valve amps is'nt worth knowing.
Lets hope it's not the output transformer.

well should not be the transformer, I am quite shure about not having done anything so dangerous to damage that. well, at least I hope...

Hi again. It looks like it is some kind of combined problem.
Yesterday I put new power tubes in the amp, and everything seemed fine. The loud growl-crack-buzz that was coming out before is not there anymore (now I remeber: it came out only after a while the amp was working).

But now a lighter crackling is there anyway, this as well coming out after some time, when the amp has been warmed up well.
There are some really quiet weird electronic noises as well, but they could be due to the bad electric system in our rehearsal room.
At this point, I think it could be some resistor..... but like I said before, I know nearly nothing about this things, so...
If anyone can help with a suggestion or hypothesis, you'll be welcome!

Hi,

I repaired a Marshall 25th nniversary combo for a client about 18 months ago, making noises, crackling banging etc.

After finding worn valve bases on the preamp, and resoldering several suspect joints, the main culprits were the EL34 output valves, but only after it had warmed up, as you have replaced the O/p valves, I'd look at the valve bases and make sure they are holding the valves tight.

Having the valves mounted upside down as in most guitar amps tends to put more heat on the valve bases. I replaced the ones in the Marshall with good quality ceramic ones.

Regards

it looks like this could be the solution, thanks wiz!
well, i hope. in fact, trying to move a bit the output valves caused some crackling, on one especially.
I'll try to fix this according to your suggestion a write back what happened.
THANKSSSSS

But I used to own a Kenwood Reciever that would from time to time pick up noise and even sometimes transmission when used at above 5 volumes from what turned out to be a neighbors ham radio set up approxamatly 3-400 meters removed from my house.

I know... There is this really low noise coming out, but it might be something due to the bad electrical system of the building, or something like that. Moving the ground switch from one position to the other does not change that at all, so I don't know. I'll try to hear that somewhere else too, just to be shure.

Welcome to the forum, Whizz, and thanks for your post. Riz, there are a number of points, and Whizz has mentioned one. I'll give you some of my ideas, but it's impossible to really solve a valve amp problem by email. A good tech is your best bet. Here are some points, though:

1. Replacing valves requires a re-bias. You can't just put another pair/quad in and expect them to work as the previous did.
2. Whizz is absolutely right. As valve bases get older, they can build up carbon gunk. This can then lead to "sparking" which is bad for your sound and the amp. They can be cleaned up or replaced with new, ceramic, bases as Whizz suggests.
3. The other thing that sounds like a problem is one or more of your filter capacitors (the "condensers" you mention). These big canisters smooth out the humps in a 50Hz or 60Hz alernating current from the mains. They were only expected to last about 15 years but many amps still have their originals after 40 years. The more an amp is used, the longer they will last, but they will fail eventually.

A good way of inspecting them is to have a look with the chassis out of the amp case. Take a good look at those cylindrical cans; top and bottom (ie, where the wiring leads in). If there is any sign of white, powdery substance around the capacitors - they must be replaced IMMEDIATELY. If not, they will explode, throwing nasty puff all over the insides of your amp. And they'll possibly bugger up several components down the line.

You really could do with a tech taking a look. At least, post some photos up here if you can.

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