Tracing noise problem, TwinRev.

[Sea Chief]

Maybe you would be best served by taking the amp to a shop.
nosaj

Im very rural. Nothing for hundreds of miles. Amp alone is Massively heavy to post to/ fro & damage possible. This option is n/a.

and If I have skills enough to build it, & it worked great before, then it's quite possible I can fix it.

I just need help, how to locate what the problem is.

Thanks, SC

[catalin gramada]

Understand this. But Ive never had one bad solder joint, ever (& often get the impression that because its known my amp knowledge is limited, that my joints are likely sub par). And isn't it just as likely, if I were to just blanket-redo them all, that I'd make one bad solder joint anyway?

I would prefer to look at components first tbh; not only bc it is a far smaller prospect in terms of workload/ it does seem logical to go for the easiest avenue first, whatever it might be to attempt fixing... no?

Furthermore if the amp worked great before, doesn't that suggest the solder joints are indeed fine? IE how would a solder joint degrade, in such a relatively short time? This avenue therefore just from logical pov, doesn't seem -that- plausible. Like the possible conductive board, Im not discounting it though.

If I could just concentrate on the component tests, before more complicated avenues, that would be great.

Thanks SC

A bad solder joint is not a joint which looks bad . An oxided terminal may be well integrated in a nice solder spot. That meant those joint may be partial conductive or not at all. Sometimes is very hard to diagnose and better to recover the flow.

[Chuck H]

A bad solder joint is not a joint which looks bad . An oxided terminal may be well integrated in a nice solder spot. That meant those joint may be partial conductive or not at all. Sometimes is very hard to diagnose and better to recover the flow.

But he's never had one before. So that can't be what's wrong. Why entertain the idea further.

[Sea Chief]

Anyone know if generally 1M is likely the value of my vol pot? (Different TR circuits have this). I do have a new cts 1meg audio pot I can swap in.

But Im still not understanding: if the noise remains with v1 pulled.. doesn't that rule out this Normal channel vol pot?

( & so swapping in a new one seems a bit illogical no-?).

Thanks, SC

[Helmholtz]

.. doesn't that rule out this Normal channel vol pot?

Kind of, yes. But then the pot should have no influence on the noise with V1 pulled.

Anyway pot value should be 1MA (maybe with a special taper like 30% or so).
You should be able to measure pot resistance from end to end with your Ohmmeter.

You could try to swap vol.pots between channels.

Could also be a bad plate resistor. Those can cause all kind of noises.
You might try freeze spray to localize a bad component.

[pdf64]

---
, is it not the case that if pulling V1 & the noise still being there.... is that not proof that Normal vol pot is ruled out as culprit?
…

So of the 9pin valves, only V6 the LTP phase splitter would be remaining?
If so, then yes.
Yes the vol pot should be 1M audio.
I recall dave h suggested replacing the pot, which given symptoms, I agree as being a good next step

[Sea Chief]

But he's never had one before. So that can't be what's wrong. Why entertain the idea further.

Thanks for the patronising sarcasm Chuck. Helpful that.

My point is simple. Resoldering all 535 solder joints takes me 2 weeks. Rebuilding the whole amp using a new board takes me 4 weeks.

So if the possibility of ONE bad component hasn't first been ruled out, as any of you would do first up if this was your faulty amp ( certainly you wouldn't just go ahead taking the whole hog & rebuild the amp with a new board without ruling out a single component first, not would you resolder all 535 solder joints without first ruling out a single component at fault either: you just wouldn't ).......

......... then for goodness sake, ruling out one solitary bad component MUST be done before these two hugely comprehensive " solutions" are even considered.

That, is just common sense. And this, is all I am asking for help on. It's not alot to ask. I know only that it's a case of going across the circuit, pulling tubes or spmething as you go ( this approximate path is all I understand). Page one stuff for you guys. NOT for me. Hence asking for help.

SC

[Sea Chief]

Kind of, yes. But then the pot should have no influence on the noise with V1 pulled.

Anyway pot value should be 1MA (maybe with a special taper like 30% or so).
You should be able to measure pot resistance from end to end with your Ohmmeter.

You could try to swap vol.pots between channels.

Could also be a bad plate resistor. Those can cause all kind of noises.
You might try freeze spray to localize a bad component.

THANK YOU HELMHOLTZ. And pdf64.

Your replies, & pdf's ( as always ) on this thread are helpful, without taking to picking at me. Appreciated.

Ok I understand that if pulling v1 ( with all remaining tubes in ) & noise continues, then even with v1 & v6 in ( & the preamp tubes between pulled ) & wiggling the Normal vol pot seemingly creating noise... then it cannot be the Normal vol pot, if simply, the noise is still there after pulling v1. I think because the first section of the circuit is completely negated once v1 is pulled**.

But just because Im only 95% sure of this**.. I replaced v1 with an identical CTS 1M-A. No difference, as expected really, noise exactly the same.

Possibly bad plate resistor? Ok now I'm cooking. You see I can, in 1 hour, change these one by one. Not in 2 fkn weeks already!!!!!!

They might not be the cause, but it's a sensible & logical next thing to do. If I rebuilt it using the original resistors.... further logic to looking at them.

( REbuild the fkn board already!!! As if ANY of you guys would even be contemplating this at such an early stage, if this amp was yours ).

Thanks, SC

[Sea Chief]

So of the 9pin valves, only V6 the LTP phase splitter would be remaining?
If so, then yes.
Yes the vol pot should be 1M audio.
I recall dave h suggested replacing the pot, which given symptoms, I agree as being a good next step

Hi pdf. Sorry I can't make sense of this reply, the wording is slightly confusing. For eg, I don't know what LTP is ( never heard of this ever ).

Ok just to reitterate. If I have all the tubes in, apart from one/ pulled, that being v1..... does this mean that a chunk of the circuit is not " live " as a result of pulling out ghis tube? (presumably looking at v1 wires, where they go to the board etc gives me indication of which physical section might now be " dead ") & also knowing that the Normal channel controls, & inputs are all " dead " too IE not working due to v1 being pulled, it tends to suggest something has changed. But what exactly I have no idea.


And is it definitive proof that these components within this " dead " v1 area are not under suspicion, IF the noise remains after pulling v1?

You see apart from the Normal channel not working having pulled v1, & presuming that doing so negates a proportion of components in & arounfd this general area... knowing precisely which ones are " turned off " or now " dead " as a result, is impossible for me to tell. Therefore I do not know if these are still in consideration as culprits, or, have been ruled out as culprits.

Thanks, SC

[nosaj]

You don't have to resolder the whole board just the area that correlates to the problem area. no need to resolder areas not in the problem section.
nosaj

[pdf64]

Seachief, I’m finding it difficult to follow what you’re reporting, sorry.
You’ve replaced the normal channel volume control, yes?
If so, please remove all 9pin valves apart from those in V1 and V6; now describe in detail any issues with the normal channel.

[Sea Chief]

You don't have to resolder the whole board just the area that correlates to the problem area. no need to resolder areas not in the problem section.
nosaj

Hi nosaj. But the problem area hasn't been isolated down, whatsoever though. If its been suggested as it has so far by a consensus ( Im sorry, but absurdly early & only bc I mentioned it had a conductive board before, not here, but where it lived a hundred miles away, for 41 years ) that the problem is a conductive board or a bad solder joint, IE without narrowing anything at all down.. then this -implies- nothing but blanket resoldering every solder.

If it had implied resoldering less than the whole amp, why hasn't this been suggested-? Because Im left high & dry. Apart from the helpful suggestion of heat drying the board, which I did, which itself implied the board - wasn't- perhaps conductive after all. Suggested. It did not conclude this I realise.

It is this narrowing down, even by 95% to start with.... which is the very very path both I know to be the correct way any amp's problem is usually done, &, what Im desperately & specifically asking for help on this thread, because I have no idea how to proceed on this path.

So, you say only a certain area needs resoldering, the one that correlates to the problem area. But if the problem area is still ' the whole amp' wuthout narrowing down - any- particular area..... Im still completely left bereft of what to do ( apart from resoldering every single joint on the amp ).

How then, how, do I isolate the amp down to the " problem area " ??? This would at least be a start !!

This is after all exactly what Ive been asking from #1.

Thanks, SC

[Sea Chief]

Seachief, I’m finding it difficult to follow what you’re reporting, sorry.
You’ve replaced the normal channel volume control, yes?
If so, please remove all 9pin valves apart from those in V1 and V6; now describe in detail any issues with the normal channel.

Hi pdf. In #53..

" I replaced v1 with an identical CTS 1M-A. No difference, as expected really, noise exactly the same. "

And I stated v1 in & v6 in, all the other preamp tubes pulled out. Noise description Ive outlined a good few times in the thread.

Thanks, SC

[Sea Chief]

pdf64 apologies as Im reading my own quoted bit in italic, it should have read thus:

" I have replaced (Normal) volume, with an identical CTS 1M-A, no difference, noise remains ".

---

So far this one component swap is all I've tried, plus fan drying the board. Nothing has changed/ noise remains.

I think the next step might be putting tubes back in, then by pulling one by one, going across, thus isolating the noise down from ' the whole amp area ' to a smaller area. But I have no idea once a tube pulled & if the noise should cease.. what / where this might signify to focus on.

So there is little point me just doing this, if I don't really know what Im doing.

SC

[nosaj]

Ok when you have all tubes in. start at V1 pull it noise still there? yes pull v2 noise still there? yes Solder area between v1 and v2. Replace tubes noise still there yes pull v1 noise still there? no solder area near v1. Simple as that. If none of that works, you possible have plate resistors to contend with. Nobody ever said this was easy or that anybody can do it as you are finding out.. There are amps I've run across that are above my limited skills you just have to know your limits.
nosaj