SuprSpy79

So my amp makes this soft crackling and white noise, kinda sounds like a camp fire. It gets REALLY bad if i flip the VPR switch. I removed all the pre-amp tubes and it still does it. I used electrical cleaner and cleaned all the sockets and reseated all the tubes. Im suspecting something on the board somewhere but I have no idea how to get access to it. I want to sell this thing but I cant sell it as it is and I dont want to spend goobers of money to get it fixed.

Any help would be GREATLY appreciated.

Marshall Amps

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Marshall Amp Forum

big dooley

maybe some loose solder joints?

stryker59

does it do it all the time or just when you are turning knobs?

__________________

you've been weighed, measured, and found wanting!

SuprSpy79

once the amp is warmed up it does it constantly. It does it with and without and instrument plugged in. I played with all the knobs wondering if it was a dirty pot, but none of them made any noise. The VPR switch makes it REALLY bad, if that helps narrow down where its coming from.

Pete240885

could be a few things, possibly a bad tube, solder joint, is the noise affected by vibration?

How old is your amp?

SuprSpy79

The amp makes the noise while sitting still. The amp is probably about 6-8 years old. The tubes are about a year old, if that, and they haven't been played that much either.

kharvelan

sounds like a bad capacitor to me, normally if a cap goes bad you get crackling, did you try and replace the power tubes? sometimes a bad power tube can do this too.

Pete240885

In my experince caps failing normally produce hum and crackle, but not white noise, but then i've seen some weird problems caused by power supply filter caps failing so i'd start there.

Swapping tubes over is easier to do though provided you know how to bias them

SuprSpy79

I pulled all the preamp tubes. I have not tried pulling the EL34's yet. Is it safe to pull those and turn on the amp still?

as far as caps, i dont even know where to look. Is there a tut anywhere on removing the circuit board from the head etc?

Pete240885

Do you have two or four EL 34s? From the "VPR" swotch i'm guessing this is either a TSL100 or a TSL122? in which case you will have four

If only two (other TSL amps) then pulling these out will be a pointless excercise as you will have absolutely no sound

If i'm right and you do indeed have four valves then try this:

Pull the pair of valves consisting of V5 and V7 out of thier sockets - If there is still a problem Pull V6 and V8, place the valves from V5 and V7 in to V6 and V8. Let me know how this goes, we'll deal with the caps later if necessary

SuprSpy79

yes I do have 4, I will give that a try later today.

Thanks for all your help I appreciate it.

Pete240885

Your welcome

Tinman

I hope no-one (especially the OP) thinks I'm rude for stepping into this thread, but the issue I have is very similar to the OP's problem.

I'm looking to buy a TSL 100. I tried it out last night and the white noise problem is there, but only when a lead is connected to the input socket. The intensity of the noise appears to be affected by operation of the gain control.
The problem seems to be on all 3 channels.
The overall sound quality is not affected by this, but it would be a major annoyance when used live

My question obviously is, whether it's going to be a major (read expensive) problem to fix (if it is then I won't buy it!)

Cheers

Pete

Edit: I should say also that it comes and goes for no reason.

Pete240885

Tinman, is it actual white noise or more of a general buzz?

Hmm as the overall tone of the amp is not affected i would rule out a valve.?

Is it on all channels or just one?

If in doubt don't buy it, have the problem fixed before hand, at the sellers expence, as its not your amp i can't ask you to open it and start poke-ing arround...Intermittent problems can be very difficult to track down also

spikei

if you've tried swapping values and leads/cables and if its not your pots you need a tech

Tinman

It's on all channels and only when you plug a lead in.....I'm thinking a dry joint perhaps.
It's a sort of rushing noise, definitely not a buzz.
I bought it anyway, thinking that it's probably nothing I can't fix myself (I'm an electrician with experience of electronics and soldering)
I'm going to start looking at it this weekend, checking the bias etc.
Is there anything that you gurus think I ought to look for in particular?

Cheers

Pete

SuprSpy79

PROBLEM SOLVED:
Ok so it was definately a bad EL34L. Using the suggestion from Pete of swapping pairs. I was able to narrow it down to the V8 tube. It makes no sound when that tube is removed, and to be sure I put another working tube in that same socket and it went away.

And for the other gentleman having the same issue. The issue happened even if no instrument cable was plugged in, and was WAY more noticeable with the vpr switch on and definately happened on all 3 channels.

Now to replace the tubes and sell this thing. Any takers? lol

Pete240885

yeah first job play with the controls in the master section, any FX controls see if they affect it and how, Gain controls/volume controls for each channel are important scene as it happens only with a lead plugged in, hopefully we can narrow this right down to one section of the amp.

Bad solder joint doesent sound like an unreasonable prediction, how does your guitar perform when the noise is present? have you tried other instruments/cables? or have you tried your guitar/cable on another amp?

spikei

ok now you got it working why do you want to sell it? you can't blame the amp for a dodgy tube.

SuprSpy79

I wanted to sell it anyway, but I couldnt sell it making noise, so i wanted to make sure it was working first. I need to downsize, im too tired lugging it around lol.

Tinman

SuprSpy79, I'm well pleased for you man, nice one.
Thanks for your patience with me jumping into your thread and with your permission I'll continue.

Pete: Without a lead connected it makes a gentle rustling noise, that is not affected by any of the controls. Once a lead is plug in: the clean channel makes a strange hissing/crackling noise and the two other channels make a roaring sound. The noise from all 3 channels is affected by the gain controls and the volume controls (turning the volumes to zero makes it silent as expected)
No other controls seem to affect the symptoms at all.

Ideas?

Cheers

Pete

Tinman

Right....I've had the back grille off. The power valves seem to be lighting up evenly, but only one of the pre-amp valves is lighting up and that's the one closest to the power valves.
I've swapped the 'good' valve into the other positions and it lights up, so it looks like I need some preamp valves then.
I'll get them and see.

Edit: Scratch that, the preamp valves are lighting up, but only faintly (are they supposed to be bright?)

Thought I'd found the problem then dammit

Tinman

So.....so far I'm wondering if I need 3 new preamp valves. The reason I missed them lighting up was because the are so faint. I'm sure they're supposed to be brighter than that.

I'm sure a guru will come along and blow that theory out of the water but hey ho.

Cheers
Pete

Pete240885

ok, try tappping each tube (lightly) with a penci when its channel is operation, check the power tubes in this manner too.

There should be some sound from them when you do this, a light amplification of the tapping, but if they screech or howl they need replacing.

If they seem ok on this test pull the pair of valves consisting of V5 and V7 out of thier sockets - If there is still a problem Pull V6 and V8, place the valves from V5 and V7 in to V6 and V8.

How does the VPR switch affect your noise?

Tinman

I must admit to not trying the vpr switch at all.
What I did notice with the preamp valves was that, although the one closest to the power valves is an ECC83 as opposed to the 12AX7's that the rest are, when I swapped the ECC83 into the other positions, it lit up brightly. The others stayed dimly lit.

I'll try that test tomorrow.....btw you say V6/V8 etc.....which are these valves?

Edit: I know that you're talking about the power valves, I meant which positions are they.

Pete240885

don't have one of these amps my self so i can't tell you, they should be labeled on the PCB i would guess that they are in and outer pairs

Tinman

ok......firstly:SuprSpy79, if you're still reading this thread, could you confirm the positions of the power valves. Someone has been in there before and marked the plate as follows: as you look at them from the back of the amp, V5-1st from the left, V7-3rd from the left. V6-2nd from the left and V8 furthest right. Pete suggested they were supposed to be inner and outer pairs, but that's not how they're marked (didn't look at the PCB btw)

Pete: ok...the VPR switch as in SuprSpy79's fault makes the noise noticeably louder.
Did the trick with the pencil and couldn't hear any amplified tapping at all.
Pulled the power valves as you suggested and it made no difference at all (that's assuming I pulled the right ones at the right time)
What I did notice though, with V8 (furthest right) was that the top of the valve was a completely different colour from the other 3. Whereas the other 3 had a nice silver end to them, V8 looked grey. Is this significant?
To recap, nothing made the noise go away (except switching the damn thing off)

Pete240885

hmm is V8 the same make and model as the others?


do you have any electronics experience/knowledge

Pete240885

That was a guess, look at the PCB it WILL be right

Tinman

All the power valves are JJ EL34's.

As for electronics experience/knowledge.....25 years ago I trained as a RAF aircraft electrician. Part of the training was in electronics (no valve theory though). Since then I've mainly concentrated on the wiring side of things, so any of the knowledge gained will be in the dark recesses of memory.
I can read a circuit diagram with no problem at all and the use of a soldering iron comes quite naturally.

I'm assuming from your question, that you feel the problem may be a bit more complicated than just a duff valve?

I'll uncover the pcb tonight and check that I got the power valves right. It does concern me however, that the one I'm calling V8 looks to me to be damaged.....it still lights up though, but I'm guessing that doesn't make any difference.

Cheers

Pete