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From: N_Cook on 29 Jun 2010 03:17
Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message
news:47bWn.34349$9c1.22170(a)hurricane...
>
>
> "N_Cook" <diverse(a)tcp.co.uk> wrote in message
> news:i0abre$2i3$1(a)news.eternal-september.org...
> > Definitely PbF, resoldering the usual suspect points.
> > I realised I was using the wrong gauge of cut down sewing needle and 2
of
> > the preamp valve socket pins are highly suspect. Those glossy white
> > ceramic
> > mounts with holes just bigger than the valve pins.
> >
> >
> If it continues to cut out, a generator, a 'scope and a meter should tell
> all. Valve circuits are very simple and very straightforward to trace
> signals in, and troubleshoot. Even if it is a bad PbF joint, it should be
> easy enough to pin it down to at least a stage, and possibly to a specific
> component, based on valve voltages.
>
> Arfa
>

Coincidence or action of high V on springiness of the socket metal?
One valve base, pin 1 , the other pin 6 , both anodes so killing throughput
if connection fails.

While on valve stuff , has anyone come across any output transformer or
mains transformer ,for that matter, in any equipment , where there is
failure of PbF joint inside the transformer where tail meets magnet wire?


From: Arfa Daily on 29 Jun 2010 04:49


"Phil Allison" <phil_a(a)tpg.com.au> wrote in message
news:i0bgp3$f5c$1(a)news-01.bur.connect.com.au...
>
> "Arfa Daily"
>>
>> If it continues to cut out, a generator, a 'scope and a meter should tell
>> all. Valve circuits are very simple and very straightforward to trace
>> signals in, and troubleshoot.
>
> ** You don't service that many valve guitar amps - do you ??



Er, that would be a yes then ... Probably three or four a week, most every
week, and have been doing them for around 40 years ... Whilst some faults
are a little obscure, most are very straightforward, and I'm sure that you
don't have any more trouble fixing them, than I do Phil. I would pick a
fault on a valve amp over a transistor one, every time, as would probably
any engineer who has ever worked with valves. Every stage is pretty much
independent, and troubleshoot-able as a separate entity. You can't say that
about most transistor amps.



>
> The ones that were originally well made are now so old they have strange
> faults most techs have never seen before - while the ones made more
> recently have designed in faults never seen before by anyone.
>
> A few examples.
>
> 1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
> when hot - output valve bias goes crazy and even the phase splitter
> stage goes way out of DC balance in normal operation because of leakage
> from anode tracks to grid tracks. There is simply no fix for this
> problem.


Care to give me a model for that behaviour ? I see a lot of Marshall combos,
as they are built just a few miles from where I live. I have not seen any
similar problems here. I used to visit Jim Marshall in his factory in the
early days. He was a very good friend of a friend of mine. As to the problem
with a - g leakage, I would have thought that you might have been able to
get away with isolating the affected tracks by cutting or even removing them
from the board completely, and then hard wiring.


>
> 2. Recent Gibson /Trace Elliot amps that develop mysterious crackling
> noises all over the circuit due to the use of water soluble flux that was
> never properly washed of the PCB. Removing the main PCB entirely and
> washing it thoroughly in solvent is the only fix.
>
> 3. Same amps as above use 9 pin PCB mount sockets that SHRINK - yep,
> the plastic material used to make the socket shrinks under the heat from
> EL84s, reducing the pitch circle diameter so much it is impossible to fit
> a new tube in the socket. Replacing all the output valve sockets is the
> only fix.
>
> Then there are all the issues with the valves themselves - all new
> production now comes from China or the former USSR and most of the valves
> have designed in faults of kinds that were never seen previously. Eg.
> nearly all 12AX7s now crackle and pop if tapped with the back of a
> screwdriver and/or have bad heater cathode hum or are very microphonic -
> while octal power types often suffer from bad soldering (PbF ?) on the
> pins causing all manner of weird intermittents when the solder joint lets
> go.


Whilst I would agree that valve quality is not as good as it was when the
likes of Mullard and Brimar etc made them, I also don't think that they are
quite as bad as you seem to find them, if you buy decent quality ones, or
manufacturer's originals, which have been vetted by the amp manufacturer as
being of the required quality. The Ruby HG (Hi Grade) 12AX7s that I use,
don't crackle and pop, and are no more microphonic than any high gain
triodes have ever been. I also don't find the h - k leakage bad either -
certainly not enough to identify as being a predominant source of unwanted
hum. And as to bad soldering on octal base pins, I honestly can't say that
I've ever seen this problem on any amp that's been across my bench, or on
any replacement valves that I have fitted, which may have had their bases
connected to the leadouts by PbF. Perhaps I've just been lucky ...


>
> Yep - fixing valve amps is pure joy.
>
>
> .... Phil
>
>

Well, I find it so ...

Arfa

From: Phil Allison on 29 Jun 2010 08:32

"Arfa Daily"
> "Phil Allison"
>>
>>> If it continues to cut out, a generator, a 'scope and a meter should
>>> tell all. Valve circuits are very simple and very straightforward to
>>> trace signals in, and troubleshoot.
>>
>> ** You don't service that many valve guitar amps - do you ??
>
>
> Er, that would be a yes then ... Probably three or four a week, most
> every week, and have been doing them for around 40 years ... Whilst some
> faults are a little obscure, most are very straightforward, and I'm sure
> that you don't have any more trouble fixing them, than I do Phil.


** I fix them all - of course.

But there is plenty of trouble with most of them.


> I would pick a fault on a valve amp over a transistor one, every time, as
> would probably any engineer who has ever worked with valves.


** Solid state gear is far easier to fix and make stay fixed - IM long E.



>> The ones that were originally well made are now so old they have strange
>> faults most techs have never seen before - while the ones made more
>> recently have designed in faults never seen before by anyone.
>>
>> A few examples.
>>
>> 1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
>> when hot - output valve bias goes crazy and even the phase splitter
>> stage goes way out of DC balance in normal operation because of leakage
>> from anode tracks to grid tracks. There is simply no fix for this
>> problem.
>
>
> Care to give me a model for that behaviour ?


** Yep - the JCM2000: TSL100 combo series.

Easy to find many stories about the same problem on usenet and web forums.


> I see a lot of Marshall combos, as they are built just a few miles from
> where I live. I have not seen any similar problems here. I used to visit
> Jim Marshall in his factory in the early days. He was a very good friend
> of a friend of mine.

** Nice guy - who never designed or built an amp in his life.


> As to the problem with a - g leakage, I would have thought that you might
> have been able to get away with isolating the affected tracks by cutting
> or even removing them from the board completely, and then hard wiring.

** Tried that idea with the very first example I ever came across.

The PCB wound up looking like a piece of Swiss cheese and still the problem
was not cured.

The only "treatment" that helped at all was to install a fan to keep the
valves and hence PCB cooler.

Colleagues have complained to me about the exact same problem.



> Whilst I would agree that valve quality is not as good as it was when the
> likes of Mullard and Brimar etc made them, I also don't think that they
> are quite as bad as you seem to find them, if you buy decent quality ones,
> or manufacturer's originals, which have been vetted by the amp
> manufacturer as being of the required quality.


** The BAD valves are already fitted in the amps that come to me for
service.

There are NO " manufacturers originals" available in Australia AFAIK.


> The Ruby HG (Hi Grade) 12AX7s that I use, don't crackle and pop, and are
> no more microphonic than any high gain triodes have ever been.

** Yaaawwwnnnnnn.....

You compare the particular with the general.

How tedious.


> I also don't find the h - k leakage bad either - certainly not enough to
> identify as being a predominant source of unwanted hum.

** How odd then that so many new generation valve amps use DC supply for
heaters JUST because of this issue.


> And as to bad soldering on octal base pins, I honestly can't say that I've
> ever seen this problem on any amp that's been across my bench,


** What planet do you live on ???



..... Phil




From: Arfa Daily on 29 Jun 2010 11:59


"Phil Allison" <phil_a(a)tpg.com.au> wrote in message
news:i0cp5t$5t2$1(a)news-01.bur.connect.com.au...
>
> "Arfa Daily"
>> "Phil Allison"
>>>
>>>> If it continues to cut out, a generator, a 'scope and a meter should
>>>> tell all. Valve circuits are very simple and very straightforward to
>>>> trace signals in, and troubleshoot.
>>>
>>> ** You don't service that many valve guitar amps - do you ??
>>
>>
>> Er, that would be a yes then ... Probably three or four a week, most
>> every week, and have been doing them for around 40 years ... Whilst some
>> faults are a little obscure, most are very straightforward, and I'm sure
>> that you don't have any more trouble fixing them, than I do Phil.
>
>
> ** I fix them all - of course.
>
> But there is plenty of trouble with most of them.
>
>
>> I would pick a fault on a valve amp over a transistor one, every time, as
>> would probably any engineer who has ever worked with valves.
>
>
> ** Solid state gear is far easier to fix and make stay fixed - IM long
> E.
>
>
>
>>> The ones that were originally well made are now so old they have strange
>>> faults most techs have never seen before - while the ones made more
>>> recently have designed in faults never seen before by anyone.
>>>
>>> A few examples.
>>>
>>> 1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
>>> when hot - output valve bias goes crazy and even the phase splitter
>>> stage goes way out of DC balance in normal operation because of leakage
>>> from anode tracks to grid tracks. There is simply no fix for this
>>> problem.
>>
>>
>> Care to give me a model for that behaviour ?
>
>
> ** Yep - the JCM2000: TSL100 combo series.
>
> Easy to find many stories about the same problem on usenet and web forums.
>
>
>> I see a lot of Marshall combos, as they are built just a few miles from
>> where I live. I have not seen any similar problems here. I used to visit
>> Jim Marshall in his factory in the early days. He was a very good friend
>> of a friend of mine.
>
> ** Nice guy - who never designed or built an amp in his life.
>
>
>> As to the problem with a - g leakage, I would have thought that you might
>> have been able to get away with isolating the affected tracks by cutting
>> or even removing them from the board completely, and then hard wiring.
>
> ** Tried that idea with the very first example I ever came across.
>
> The PCB wound up looking like a piece of Swiss cheese and still the
> problem was not cured.
>
> The only "treatment" that helped at all was to install a fan to keep the
> valves and hence PCB cooler.
>
> Colleagues have complained to me about the exact same problem.
>
>
>
>> Whilst I would agree that valve quality is not as good as it was when the
>> likes of Mullard and Brimar etc made them, I also don't think that they
>> are quite as bad as you seem to find them, if you buy decent quality
>> ones, or manufacturer's originals, which have been vetted by the amp
>> manufacturer as being of the required quality.
>
>
> ** The BAD valves are already fitted in the amps that come to me for
> service.
>
> There are NO " manufacturers originals" available in Australia AFAIK.
>
>
>> The Ruby HG (Hi Grade) 12AX7s that I use, don't crackle and pop, and are
>> no more microphonic than any high gain triodes have ever been.
>
> ** Yaaawwwnnnnnn.....
>
> You compare the particular with the general.
>
> How tedious.
>
>
>> I also don't find the h - k leakage bad either - certainly not enough to
>> identify as being a predominant source of unwanted hum.
>
> ** How odd then that so many new generation valve amps use DC supply for
> heaters JUST because of this issue.
>
>
>> And as to bad soldering on octal base pins, I honestly can't say that
>> I've ever seen this problem on any amp that's been across my bench,
>
>
> ** What planet do you live on ???
>
>
>
> .... Phil
>


Apparently, a very different one from you ...

But then, of course, I was forgetting who I was trying to have a reasoned
discussion with. It had completely slipped my mind that anyone who looks at
anything from a different point of view to you, must be wrong. I suppose
you'll start in on the hysterical abuse hurling next. Well, if that's what
you need to do, go right ahead. I really don't care. And I suppose you know
Jim all the way from upside down land do you ?

Arfa
>
From: Geoffrey S. Mendelson on 29 Jun 2010 15:24
Arfa Daily wrote:
> Er, that would be a yes then ... Probably three or four a week, most every
> week, and have been doing them for around 40 years

If you are such an expert, please tell us how they got that volume
control to go to 11, while (whilst?) everyone knows they only go to 10?

:-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm(a)mendelson.com N3OWJ/4X1GM
I do multitasking. If that bothers you, file a complaint and I will start
ignoring it immediately.
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