Iain Churches wrote:
"Rob" wrote in message
...
Fleetie wrote:
Hi.

While I'm here, does anyone know the usual cause for a valve amp
constantly "rustling" out of one channel? Mine is doing it
intermittently and sometimes loudly, out of the left channel.
Is it likely to be a resistor burning up, or something about
the valves? Is it likely to be in the output stage valves or
cathode resistors, or...? It's starting to drive me nuts!

Is this the kind of symptom that tends to always have the same
cause?

Thanks for any pointers.
In my limited experience (er, once), it was down to a faulty valve. One of
the big ones.

It can be all manner of things, so you need to make a list and start at
the beginning. It might be a dry joint somewhere. Whatever it is, it
can be found with systematical searching. The hi-tech methods of
a) wiggling and b) tapping usually provide the answer.


Agreed. The beginning for me, though, is to look at the valves, see if
one looks a bit peeky, and change if there's doubt. As I say, it worked
for me so it may work for Fleetie. One of the big chunky valves rather
than one of the tiddlers in my case. That, along with the wiggle and
reseat, is the extent of my system.

Rob

"Rob" wrote in message
...
Iain Churches wrote:
"Rob" wrote in message
...
Fleetie wrote:
Hi.

While I'm here, does anyone know the usual cause for a valve amp
constantly "rustling" out of one channel? Mine is doing it
intermittently and sometimes loudly, out of the left channel.
Is it likely to be a resistor burning up, or something about
the valves? Is it likely to be in the output stage valves or
cathode resistors, or...? It's starting to drive me nuts!

Is this the kind of symptom that tends to always have the same
cause?

Thanks for any pointers.
In my limited experience (er, once), it was down to a faulty valve. One
of the big ones.

It can be all manner of things, so you need to make a list and start at
the beginning. It might be a dry joint somewhere. Whatever it is, it
can be found with systematical searching. The hi-tech methods of
a) wiggling and b) tapping usually provide the answer.


Agreed. The beginning for me, though, is to look at the valves, see if one
looks a bit peeky, and change if there's doubt. As I say, it worked for me
so it may work for Fleetie. One of the big chunky valves rather than one
of the tiddlers in my case. That, along with the wiggle and reseat, is the
extent of my system.

Yes. Your methodology is sound. I have the luxury of two
AVO Mk IV valve testers in the workshop which I share,
but still, a visual inspection is a good first step. In my experience,
rustling is usually associated with small signal valves, (miniature
nine pins in particular) so "swoppin an' listenin' usually finds the
culprit.

Iain

In article ,
Fleetie wrote:
While I'm here, does anyone know the usual cause for a valve amp
constantly "rustling" out of one channel? Mine is doing it
intermittently and sometimes loudly, out of the left channel.
Is it likely to be a resistor burning up, or something about
the valves? Is it likely to be in the output stage valves or
cathode resistors, or...? It's starting to drive me nuts!

One guess would be a leaky capacitor.

--
*Happiness is seeing your mother-in-law on a milk carton

Dave Plowman London SW
To e-mail, change noise into sound.

As said, leaky capacitor, bad contact on sockets and valves
themselves, plus dry joints.

Dry joints have been the commonest cause in my experience. If you use
point to point wiring and ANY older parts (tag strips, sockets), you
are at the mercy of the metal surfaces - these can be oxidised, dirty
or even just plain badly made from metal that won't solder properly.

Since all the above can be found in valve amplifiers of a certain age,
you sometimes need to re-solder all the contacts to eliminate a
stubborn rustling. Could be a hairline crack in a joint, could be
virtually invisible. The rustling is presumably some sort of bad or
intermittent contact in these cases. I've usually cured this by re-
soldering the joints around where the rustling comes - you can
generally localise it by a certain amount of trial and error. Mostly
it was valve bases.

Fleetie wrote:

While I'm here, does anyone know the usual cause for a valve amp
constantly "rustling" out of one channel? Mine is doing it
intermittently and sometimes loudly, out of the left channel.
Is it likely to be a resistor burning up, or something about
the valves? Is it likely to be in the output stage valves or
cathode resistors, or...? It's starting to drive me nuts!

Is this the kind of symptom that tends to always have the same
cause?

Thanks for any pointers.

Does it contain any carbon composition resistors ? Or ancient leaky
coupling caps ?

Graham

Does it contain any carbon composition resistors ? Or ancient leaky
coupling caps ?

Graham

It's only 4 years old so caps should be fine, I think.

This is one of the ultra-cheap Chinese jobs, so manufactured on
the serious cheap.

It sounds nice when it's behaving itself, but it's a PITA.

A bit like a high-maintenance girlfriend.


Martin

In article ,
Fleetie wrote:
It's only 4 years old so caps should be fine, I think.

This is one of the ultra-cheap Chinese jobs, so manufactured on
the serious cheap.

Caps can be one of the first things to suffer quality wise when things are
made on the cheap. Especially considering some of the voltages involved.

--
*Your kid may be an honours student, but you're still an idiot.

Dave Plowman London SW
To e-mail, change noise into sound.

Fleetie wrote:

Does it contain any carbon composition resistors ? Or ancient leaky
coupling caps ?

It's only 4 years old so caps should be fine, I think.

This is one of the ultra-cheap Chinese jobs, so manufactured on
the serious cheap.

Don't rule out any 'iffy' passive components then. The quality of Chinese
parts varies from excellent to abominable.

At only 4 years I'm very doubtful about any ideas relating to corroded
valve bases unless you stored it in a basement for ages.

Of course, valve swapping should sort out any possibilities there.
Remember to only swap one at a time.

Graham

Eeyore wrote:

At only 4 years I'm very doubtful about any ideas relating to corroded
valve bases unless you stored it in a basement for ages.

Of course, valve swapping should sort out any possibilities there.
Remember to only swap one at a time.

Agreeing with this advice is a section on troubleshooting problems in a valve amp manual I translated for a German manufacturer last week:

"Noise, crackling or similar undesirable noises can be caused by residual gas or other residues in the tubes. This kind of noise does not often reach a level that could be considered annoying, although the nearer to the "front" the particular tube is, the more it will tend to make itself felt. In the V 80, this would be tube V 6. As it is rare for both systems in a double triode to be equally affected, the noise levels in each stereo channel will be different. If you experience noise that is louder on one channel than on the other, the first thing to do is to change the V 6 tube (ECC 81/6072)."

Stephen

"Stephen McLuckie" wrote in message
et...
Eeyore wrote:

At only 4 years I'm very doubtful about any ideas relating to corroded
valve bases unless you stored it in a basement for ages.

Of course, valve swapping should sort out any possibilities there.
Remember to only swap one at a time.

Agreeing with this advice is a section on troubleshooting problems in a
valve amp manual I translated for a German manufacturer last week:

"Noise, crackling or similar undesirable noises can be caused by residual
gas or other residues in the tubes. This kind of noise does not often
reach a level that could be considered annoying, although the nearer to
the "front" the particular tube is, the more it will tend to make itself
felt. In the V 80, this would be tube V 6. As it is rare for both systems
in a double triode to be equally affected, the noise levels in each stereo
channel will be different. If you experience noise that is louder on one
channel than on the other, the first thing to do is to change the V 6 tube
(ECC 81/6072)."


Yes., The front end is definately the place to start with
such a fault.

Many amps use Chinese ceramic valve bases. They are
variable, and poor pin contact is a common cause of
crackling/rustling.

Changing over valves in pairs is a very quick way to
locate a faulty one.

Iain