Recent Marshall amps - safety issue.

[N Cook]

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the pots
with star washers under the bush nuts or fascia. So even in careful useage
the nuts work loose in a couple of years which is fine inside an electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety issue
there. But not for valve amps - needs a modification to stop each of the
pots rotating and then bare connections touching.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[N Cook]

Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...

Eeyore wrote:

N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.

Irrelevant probably. As long as there's no shock risk to the user, it's
fine.

I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.

I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron

If you must know, replace plain washers with spring washers to reduce chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip, soldered
to each pot case, the sort of enamelled high current wire used in some power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard, 3/8
wide cable-tie with the fastener cut off , bridging the back of each pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his amp,
FFS , well he can cut them off himself. But I am obliged to make some sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed, not pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Gareth Magennis]

"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...

Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:

N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent
models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.

Irrelevant probably. As long as there's no shock risk to the user, it's
fine.

I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.

I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron

If you must know, replace plain washers with spring washers to reduce
chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip,
soldered
to each pot case, the sort of enamelled high current wire used in some
power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard, 3/8
wide cable-tie with the fastener cut off , bridging the back of each pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his
amp,
FFS , well he can cut them off himself. But I am obliged to make some sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed, not pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Well if my car came back from Kwik Fit with all sorts of extra wires and
ties holding the exhaust on "better", I'd wonder WTF the fitter thought he
was doing, and how much he had charged me for the priviledge.


Gareth.

 

[N Cook]

jakdedert <jakdedert@bellsouth.net> wrote in message
news:NBRvk.21665$XB4.6016@bignews9.bellsouth.net...

Gareth Magennis wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent
models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured
the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n
safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.
Irrelevant probably. As long as there's no shock risk to the user,
it's
fine.
I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.
I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept
the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it
being
modified from box standard in any way.

Ron
If you must know, replace plain washers with spring washers to reduce
chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot
is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip,
soldered
to each pot case, the sort of enamelled high current wire used in some
power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard,
3/8
wide cable-tie with the fastener cut off , bridging the back of each
pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his
amp,
FFS , well he can cut them off himself. But I am obliged to make some
sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed, not
pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Well if my car came back from Kwik Fit with all sorts of extra wires and
ties holding the exhaust on "better", I'd wonder WTF the fitter thought
he
was doing, and how much he had charged me for the priviledge.


Gareth.


I'm somewhere in between. Given a real issue with future reliability, I
appreciate the attention paid. OTOH, it's a sales job for the
technician as to the utility of such modification.

Many, many guitars (and other kit--I like that particularly British
term) do indeed exhibit the loose pot--and loose jakc--syndrome. Most
experienced players carry tools to tighten the nuts, forestalling or
eliminating future failure...and consider it to be just another part of
regular maintenance--like adjusting the bridge or filing frets. Less
experienced players either have not seen the problem, or if so, believe
it to be an issue with their particular instrument. They are the ones
who would benefit most, and be hardest to sell.

As for the Marshall amp, again, many bought the unit on the strength of
reputation. They're possibly not ever going to use it enough for the
issue to exhibit. Those who do will either believe their case to be
unique, or at least unusual. Pros will either appreciate the fix, or
move on to more reliable brands (or more solidly constructed vintage
originals).

So, I see the issue as a sales job. Unlike my vehicle (I look under
mine regularly, but how many people do?), the mods made by Mr. Cook are
only going to manifest in the absence of future problems, or in the
telling by him. He'll either have to justify the extra expense, or
simply absorb it.

As to the actual fix, all those outlined sound viable to me. I think
I'd go for a multi-pronged approach. In fact using all of them is not
without merit for a unit which needs to be bullet-proof in daily
professional use--and these are the customers who will appreciate (and
pay for) the extra attention. Additionally, a 'chemical' solution seems
indicated. Applying a thread locking compound to the nuts would help.
'Painting' the nut to the shaft and panel with something like fingernail
polish is an effective, simple fix which requires no removal of the
actual pot hardware...adding little shop time for the tech to justify
the expense of.

jak

These amps have a printed plastic finnish covering over the fascia metal.
With a thread lock chemical approach the plastic can still compress under
the bush nuts ,microscopically, plus metal creep and soon the pots will
turn if the knob is rotated to either endstop.

The anti-rotation lugs are there for chassis mount ring tagged and wired
pots precisely to stop any chance of rotation - up until the point is
reached when the the pot has fallen off , that is.

If the wiring was loomed and laced tight it would be a reasonably
satisfactory alternative .

Kit and kaboodle is the full term but I don't know what a kaboodle is or
was.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Smitty Two]

In article <g9oscu$dv5$1@inews.gazeta.pl>,
"N Cook" <diverse8@gazeta.pl> wrote:

These amps have a printed plastic finish covering over the fascia metal.
With a thread lock chemical approach the plastic can still compress under
the bush nuts ,microscopically, plus metal creep and soon the pots will
turn if the knob is rotated to either endstop.

DAMHIK that threadlock compound eats plastic, too. Definitely not the
anti-rotation scheme of choice around plastic.

 

[N Cook]

Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:vIadnaekxa0PdiLVnZ2dnUVZ8jWdnZ2d@bt.com...

jakdedert wrote:
Gareth Magennis wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:

If someone decided that they would take it upon themselves to 'rewire'
my vintage Gibson, I`d be a might annoyed to say the least.

Ron(UK)

So, say you were non-techie and someone was repairing your vintage Gibson
noticed that some of the rubber insulation over the HT or mains wiring was
perished and cracking off - you would say oh that's fine its of no
consequence, leave it, as its original. ?

I see nothing intrinsically wrong with the vintage bods who remove the
wrappers from ancient leaky paper capacitors, sorry condensers, and replace
with modern functional polypropylene ones covered with the original wrapper.
But safety matters are something else.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Gareth Magennis]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:NBRvk.21665$XB4.6016@bignews9.bellsouth.net...

Gareth Magennis wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent
models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured
the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.
Irrelevant probably. As long as there's no shock risk to the user,
it's
fine.
I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.
I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept
the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron
If you must know, replace plain washers with spring washers to reduce
chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot
is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip,
soldered
to each pot case, the sort of enamelled high current wire used in some
power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard,
3/8
wide cable-tie with the fastener cut off , bridging the back of each
pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his
amp,
FFS , well he can cut them off himself. But I am obliged to make some
sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed, not
pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Well if my car came back from Kwik Fit with all sorts of extra wires and
ties holding the exhaust on "better", I'd wonder WTF the fitter thought
he was doing, and how much he had charged me for the priviledge.


Gareth.
I'm somewhere in between. Given a real issue with future reliability, I
appreciate the attention paid. OTOH, it's a sales job for the technician
as to the utility of such modification.

Many, many guitars (and other kit--I like that particularly British term)
do indeed exhibit the loose pot--and loose jakc--syndrome. Most
experienced players carry tools to tighten the nuts, forestalling or
eliminating future failure...and consider it to be just another part of
regular maintenance--like adjusting the bridge or filing frets. Less
experienced players either have not seen the problem, or if so, believe it
to be an issue with their particular instrument. They are the ones who
would benefit most, and be hardest to sell.

As for the Marshall amp, again, many bought the unit on the strength of
reputation. They're possibly not ever going to use it enough for the
issue to exhibit. Those who do will either believe their case to be
unique, or at least unusual. Pros will either appreciate the fix, or move
on to more reliable brands (or more solidly constructed vintage
originals).

I repair a LOT of Marshalls. I can't remember ever seeing a pot that has
been turned around on its mounting. Plenty that have got bashed from the
front or the shaft broken off, and possibly some that have actually been
turned with too much force, and the pot has disintegrated internally
instead.

Sure, make something better where it is appropriate, and with the
appropriate skills and method, which I often do. Lashing a whole bunch of
pots with a whole bunch of cable ties does not fit in with my version of
appropriate. Sound more like some over enthusiastic bodging. I would not
be pleased to see that on my amp, car, bicycle, chimney stack, cat, etc.



Gareth.

So, I see the issue as a sales job. Unlike my vehicle (I look under mine
regularly, but how many people do?), the mods made by Mr. Cook are only
going to manifest in the absence of future problems, or in the telling by
him. He'll either have to justify the extra expense, or simply absorb it.

As to the actual fix, all those outlined sound viable to me. I think I'd
go for a multi-pronged approach. In fact using all of them is not without
merit for a unit which needs to be bullet-proof in daily professional
use--and these are the customers who will appreciate (and pay for) the
extra attention. Additionally, a 'chemical' solution seems indicated.
Applying a thread locking compound to the nuts would help. 'Painting' the
nut to the shaft and panel with something like fingernail polish is an
effective, simple fix which requires no removal of the actual pot
hardware...adding little shop time for the tech to justify the expense of.

jak

 

[Arfa Daily]

"Gareth Magennis" <sound.service@btconnect.com> wrote in message >> Gareth
Magennis wrote:

I repair a LOT of Marshalls. I can't remember ever seeing a pot that has
been turned around on its mounting. Plenty that have got bashed from the
front or the shaft broken off, and possibly some that have actually been
turned with too much force, and the pot has disintegrated internally
instead.

Sure, make something better where it is appropriate, and with the
appropriate skills and method, which I often do. Lashing a whole bunch of
pots with a whole bunch of cable ties does not fit in with my version of
appropriate. Sound more like some over enthusiastic bodging. I would not
be pleased to see that on my amp, car, bicycle, chimney stack, cat, etc.



Gareth.

We see a lot of poor design these days, but I think in the end, we just have
to live with it. Today, for instance, I had a 'modern' version of the Vox
AC15 on the bench. For a start, you can't even get at the output valves,
without removing the chassis, so that's not too clever for 'on the road'
maintenance for a start. The problem with this particular amp was that the
sound was very 'thin', and there was a substantial amount of hum
continuously present. When I had the chassis out, it was clear that one of
the output valves was seriously distressed, with its anode glowing red hot.
I reached for my meter and probed the control grid pin on the affected
valve, and the wire just fell off. These are chassis mounted valve bases,
with wires going back to the nearby pcb, and what sort of wire have they
used ? Thin single strand, about like telephone extension wire. The wire had
neatly broken just at the end of the insulation.

Now I know these Voxs are built in China now under license, but they are
designed in the UK for goodness sake. Who in their right mind, would use
thin rigid single strand wire in a bit of kit that is going to be bounced
around on the road as part of its normal natural working life ? And what on
earth was the designer's team leader thinking of, when he signed off on this
to production ? I think that the inaccessibility of the output valves, and
the use of this type of wire for internal hookups, are both inexcusable
design errors, and not the sort of thing that serious users would be
expecting from a (formerly) reputable name like Vox. The wiring issue is a
good example of what *could* be done by a service engineer to improve future
reliability. He could replace all of those flying wires to the valve sockets
with multistrand ones, but should he ? Would it be worth it ? Would the
owner appreciate and pay for it ? I think I'm with everyone else on this
one, and the answer is "no" on all three counts ...

Arfa

 

[N Cook]

Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:Yx%vk.108293$le1.20177@newsfe11.ams2...

"Gareth Magennis" <sound.service@btconnect.com> wrote in message >> Gareth
Magennis wrote:


I repair a LOT of Marshalls. I can't remember ever seeing a pot that
has
been turned around on its mounting. Plenty that have got bashed from
the
front or the shaft broken off, and possibly some that have actually been
turned with too much force, and the pot has disintegrated internally
instead.

Sure, make something better where it is appropriate, and with the
appropriate skills and method, which I often do. Lashing a whole bunch
of
pots with a whole bunch of cable ties does not fit in with my version of
appropriate. Sound more like some over enthusiastic bodging. I would
not
be pleased to see that on my amp, car, bicycle, chimney stack, cat, etc.



Gareth.

We see a lot of poor design these days, but I think in the end, we just
have
to live with it. Today, for instance, I had a 'modern' version of the Vox
AC15 on the bench. For a start, you can't even get at the output valves,
without removing the chassis, so that's not too clever for 'on the road'
maintenance for a start. The problem with this particular amp was that the
sound was very 'thin', and there was a substantial amount of hum
continuously present. When I had the chassis out, it was clear that one of
the output valves was seriously distressed, with its anode glowing red
hot.
I reached for my meter and probed the control grid pin on the affected
valve, and the wire just fell off. These are chassis mounted valve bases,
with wires going back to the nearby pcb, and what sort of wire have they
used ? Thin single strand, about like telephone extension wire. The wire
had
neatly broken just at the end of the insulation.

Now I know these Voxs are built in China now under license, but they are
designed in the UK for goodness sake. Who in their right mind, would use
thin rigid single strand wire in a bit of kit that is going to be bounced
around on the road as part of its normal natural working life ? And what
on
earth was the designer's team leader thinking of, when he signed off on
this
to production ? I think that the inaccessibility of the output valves, and
the use of this type of wire for internal hookups, are both inexcusable
design errors, and not the sort of thing that serious users would be
expecting from a (formerly) reputable name like Vox. The wiring issue is a
good example of what *could* be done by a service engineer to improve
future
reliability. He could replace all of those flying wires to the valve
sockets
with multistrand ones, but should he ? Would it be worth it ? Would the
owner appreciate and pay for it ? I think I'm with everyone else on this
one, and the answer is "no" on all three counts ...

Arfa

A fudge fix there would be replace the defective wire and dabs of RTV on the
exposed ends of the remaining ones.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[Gareth Magennis]

"jakdedert" <jakdedert@bellsouth.net> wrote in message
news:MMcwk.23347$Ep1.5398@bignews2.bellsouth.net...

Michael A. Terrell wrote:
N Cook wrote:
A fudge fix there would be replace the defective wire and dabs of RTV on
the
exposed ends of the remaining ones.


The proper repair would be to replace all the questionable wire while
it is on your bench.


Doing that--especially if the entire unit is 'questionable'--is not always
proper. Well, it's 'proper' in the sense that it's the right way to
repair something; but improper if the client is not willing to pay for the
bench time. On most gear the cost would exceed the value of the finished
product. As a business, you can't afford to re-engineer every piece of
gear that comes across your bench, at your own expense.

Better to fix the obvious problems, explain that it may reoccur and hand
it back...or forgo any repair at all. With just about *everything* these
days being engineered to the bottom line, you've just hit on the reason
for the demise of the local repair shop.

jak

But the advantage to the customer is that he can buy a "Vox AC30" for 500
quid. Anyone know how much, in todays terms, an AC 30 cost in the 60's?
I saw an old price list of the HiWatt range a while back but can't find it
on the Net now. Anyway an amp and cab I'm pretty sure came in at over
Ł3000. And that was 1970's prices.



Gareth.

 

[Arfa Daily]

"boardjunkie" <boardjunkie@techie.com> wrote in message
news:4bc58128-c7e9-4126-84a5-ba19b4582121@m73g2000hsh.googlegroups.com...
On Sep 4, 9:01 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

We see a lot of poor design these days, but I think in the end, we just
have
to live with it. Today, for instance, I had a 'modern' version of the Vox
AC15 on the bench. For a start, you can't even get at the output valves,
without removing the chassis, so that's not too clever for 'on the road'
maintenance for a start.

Ugh.....don't get me started on those China reissues......

Which are, never-the-less, still supposedly designed here in the UK by a
company who should know better, after how long they've been in the business,
would you not agree ?

Arfa

 

[Eeyore]

N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the pots
with star washers under the bush nuts or fascia. So even in careful useage
the nuts work loose in a couple of years which is fine inside an electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety issue
there. But not for valve amps - needs a modification to stop each of the
pots rotating and then bare connections touching.

Irrelevant probably. As long as there's no shock risk to the user, it's fine.

I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from some of
the best. Since around 1987. You might say it makes the product unreliable ?
Nought to do with safety.

Graham

 

[Ron(UK)]

Eeyore wrote:

N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the pots
with star washers under the bush nuts or fascia. So even in careful useage
the nuts work loose in a couple of years which is fine inside an electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety issue
there. But not for valve amps - needs a modification to stop each of the
pots rotating and then bare connections touching.

Irrelevant probably. As long as there's no shock risk to the user, it's fine.

I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from some of
the best. Since around 1987. You might say it makes the product unreliable ?
Nought to do with safety.

I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron

 

[Eeyore]

"Ron(UK)" wrote:

Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the pots
with star washers under the bush nuts or fascia. So even in careful useage
the nuts work loose in a couple of years which is fine inside an electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety issue
there. But not for valve amps - needs a modification to stop each of the
pots rotating and then bare connections touching.

Irrelevant probably. As long as there's no shock risk to the user, it's fine.

I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from some of
the best. Since around 1987. You might say it makes the product unreliable ?
Nought to do with safety.

I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Besides they mount with 3 terminals presumably to a pcb these days. That satisfies
just about everyone I know.

Graham

 

[Ron(UK)]

N Cook wrote:

Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.
Irrelevant probably. As long as there's no shock risk to the user, it's
fine.
I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.
I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron

If you must know, replace plain washers with spring washers to reduce chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip, soldered
to each pot case, the sort of enamelled high current wire used in some power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard, 3/8
wide cable-tie with the fastener cut off , bridging the back of each pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his amp,
FFS , well he can cut them off himself.

But I am obliged to make some sort of remedial works.

Personally, I dont think you are. Whilst I might agree with you about
the spring washers, modifying the construction method of an item of kit
which has already passed whatever required regulations, could in my view
leave you open to liability if something goes pearshaped in the future.

What say you Graham, you know a lot more about this than me?

Ron

 

[Eeyore]

"Ron(UK)" wrote:

N Cook wrote:

If the owner does not like the appearance of such on the INSIDE of his amp,
FFS , well he can cut them off himself.

But I am obliged to make some sort of remedial works.

Personally, I dont think you are. Whilst I might agree with you about
the spring washers, modifying the construction method of an item of kit
which has already passed whatever required regulations, could in my view
leave you open to liability if something goes pearshaped in the future.

What say you Graham, you know a lot more about this than me?

Don't bugger about with it is my advice. You could negate the safety approvals.

If it was born shit it will die shit.

Graham

 

[jakdedert]

Gareth Magennis wrote:

"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent
models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.
Irrelevant probably. As long as there's no shock risk to the user, it's
fine.
I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.
I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron
If you must know, replace plain washers with spring washers to reduce
chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each pot is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip,
soldered
to each pot case, the sort of enamelled high current wire used in some
power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard, 3/8
wide cable-tie with the fastener cut off , bridging the back of each pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of his
amp,
FFS , well he can cut them off himself. But I am obliged to make some sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed, not pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Well if my car came back from Kwik Fit with all sorts of extra wires and
ties holding the exhaust on "better", I'd wonder WTF the fitter thought he
was doing, and how much he had charged me for the priviledge.


Gareth.


I'm somewhere in between. Given a real issue with future reliability, I

appreciate the attention paid. OTOH, it's a sales job for the
technician as to the utility of such modification.

Many, many guitars (and other kit--I like that particularly British
term) do indeed exhibit the loose pot--and loose jakc--syndrome. Most
experienced players carry tools to tighten the nuts, forestalling or
eliminating future failure...and consider it to be just another part of
regular maintenance--like adjusting the bridge or filing frets. Less
experienced players either have not seen the problem, or if so, believe
it to be an issue with their particular instrument. They are the ones
who would benefit most, and be hardest to sell.

As for the Marshall amp, again, many bought the unit on the strength of
reputation. They're possibly not ever going to use it enough for the
issue to exhibit. Those who do will either believe their case to be
unique, or at least unusual. Pros will either appreciate the fix, or
move on to more reliable brands (or more solidly constructed vintage
originals).

So, I see the issue as a sales job. Unlike my vehicle (I look under
mine regularly, but how many people do?), the mods made by Mr. Cook are
only going to manifest in the absence of future problems, or in the
telling by him. He'll either have to justify the extra expense, or
simply absorb it.

As to the actual fix, all those outlined sound viable to me. I think
I'd go for a multi-pronged approach. In fact using all of them is not
without merit for a unit which needs to be bullet-proof in daily
professional use--and these are the customers who will appreciate (and
pay for) the extra attention. Additionally, a 'chemical' solution seems
indicated. Applying a thread locking compound to the nuts would help.
'Painting' the nut to the shaft and panel with something like fingernail
polish is an effective, simple fix which requires no removal of the
actual pot hardware...adding little shop time for the tech to justify
the expense of.

jak

 

[Ron(UK)]

jakdedert wrote:

Gareth Magennis wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:
N Cook wrote:

Certainly for a model 1987X from 2006 and probably other recent
models.

To save cutting small holes in the front fascia, to take the pot
ant-rotation lugs, they've cut them off and then not even secured
the
pots
with star washers under the bush nuts or fascia. So even in careful
useage
the nuts work loose in a couple of years which is fine inside an
electric
quitar , just a rat's nest of knotted signal wires, no elf 'n safety
issue
there. But not for valve amps - needs a modification to stop each of
the
pots rotating and then bare connections touching.
Irrelevant probably. As long as there's no shock risk to the user,
it's
fine.
I am a fairly experienced safety (and EMC) 'expert' btw. Ilearnt from
some of
the best. Since around 1987. You might say it makes the product
unreliable ?
Nought to do with safety.
I was quite wondering just how Mr Cook was intending to 'modify' the
mounting of pots - if the anti rotation peg is broken off, surely he`s
going to have to replace all the pots, and drill the panel to accept
the
peg. Either that, or bodge something up? Either way I can`t see the
proud owner of a nice new Marshall amp being too chuffed about it being
modified from box standard in any way.

Ron
If you must know, replace plain washers with spring washers to reduce
chance
of nuts slackening in the first place.

The 1mm tinned copper wire earth strap soldered to and across each
pot is
not enough to stop, wire breaking and the pots rotating.

If in an electric guitar I replace the wire with flat copper strip,
soldered
to each pot case, the sort of enamelled high current wire used in
some power
transformers, with the enamelling stripped off..
In these sorts of cases, not wishing to add to any electrical hazard,
3/8
wide cable-tie with the fastener cut off , bridging the back of each
pot,
and then 1/8 inch cable ties around each pot and the wide nylon.

If the owner does not like the appearance of such on the INSIDE of
his amp,
FFS , well he can cut them off himself. But I am obliged to make some
sort
of remedial works.

Traditional chassis mounted pots ie with loose wiring, not loomed,
not pcb
mount ones.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Well if my car came back from Kwik Fit with all sorts of extra wires
and ties holding the exhaust on "better", I'd wonder WTF the fitter
thought he was doing, and how much he had charged me for the priviledge.


Gareth.

I'm somewhere in between. Given a real issue with future reliability, I
appreciate the attention paid. OTOH, it's a sales job for the
technician as to the utility of such modification.

Many, many guitars (and other kit--I like that particularly British
term) do indeed exhibit the loose pot--and loose jakc--syndrome. Most
experienced players carry tools to tighten the nuts, forestalling or
eliminating future failure...and consider it to be just another part of
regular maintenance--like adjusting the bridge or filing frets. Less
experienced players either have not seen the problem, or if so, believe
it to be an issue with their particular instrument. They are the ones
who would benefit most, and be hardest to sell.

As for the Marshall amp, again, many bought the unit on the strength of
reputation. They're possibly not ever going to use it enough for the
issue to exhibit. Those who do will either believe their case to be
unique, or at least unusual. Pros will either appreciate the fix, or
move on to more reliable brands (or more solidly constructed vintage
originals).

So, I see the issue as a sales job. Unlike my vehicle (I look under
mine regularly, but how many people do?), the mods made by Mr. Cook are
only going to manifest in the absence of future problems, or in the
telling by him. He'll either have to justify the extra expense, or
simply absorb it.

As to the actual fix, all those outlined sound viable to me. I think
I'd go for a multi-pronged approach. In fact using all of them is not
without merit for a unit which needs to be bullet-proof in daily
professional use--and these are the customers who will appreciate (and
pay for) the extra attention.

Additionally, a 'chemical' solution seems
indicated. Applying a thread locking compound to the nuts would help.
'Painting' the nut to the shaft and panel with something like fingernail
polish is an effective, simple fix which requires no removal of the
actual pot hardware...adding little shop time for the tech to justify
the expense of.

Which is the approach I myself adopt.

If someone decided that they would take it upon themselves to 'rewire'
my vintage Gibson, I`d be a might annoyed to say the least.

Ron(UK)

 

[Ron(UK)]

N Cook wrote:
<snip>

These amps have a printed plastic finnish covering over the fascia metal.
With a thread lock chemical approach the plastic can still compress under
the bush nuts ,microscopically, plus metal creep and soon the pots will
turn if the knob is rotated to either endstop.

The anti-rotation lugs are there for chassis mount ring tagged and wired
pots precisely to stop any chance of rotation - up until the point is
reached when the the pot has fallen off , that is.

If the wiring was loomed and laced tight it would be a reasonably
satisfactory alternative .

I`d put the star washers on the inside - metal to metal - and lock with
varnish or glue also on the inside. I use pva adhesive as it holds fast,
is slightly flexible so doesnt crack yet can be easily removed if need be.

If you're determined to stop the pots rotating, how about soldering a
length of stiff copper wire right along the tops of all the pots,
directly to the cases? that`s often done any way to bond them all together.

Kit and kaboodle is the full term but I don't know what a kaboodle is or
was.

Kit meaning equipment comes from kitbag. caboodle means property

Ron(UK)

 

[Ron(UK)]

N Cook wrote:

Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:vIadnaekxa0PdiLVnZ2dnUVZ8jWdnZ2d@bt.com...
jakdedert wrote:
Gareth Magennis wrote:
"N Cook" <diverse8@gazeta.pl> wrote in message
news:g9oin3$so3$1@inews.gazeta.pl...
Ron(UK) <ron@lunevalleyaudio.com> wrote in message
news:zKudnfrkAOO9IyLVnZ2dneKdnZydnZ2d@bt.com...
Eeyore wrote:


If someone decided that they would take it upon themselves to 'rewire'
my vintage Gibson, I`d be a might annoyed to say the least.

Ron(UK)


So, say you were non-techie and someone was repairing your vintage Gibson
noticed that some of the rubber insulation over the HT or mains wiring was
perished and cracking off - you would say oh that's fine its of no
consequence, leave it, as its original. ?

Well, firstly Gibson guitars don`t have much in the way of mains or HT
wiring.

However say it was a vintage amplifier I was repairing, of course I
would replace defective wiring with new, but I`d try to keep it in the
spirit of the original, I certainly wouldn`t chop and change it around
on my own personal whim or paranoia.

I see nothing intrinsically wrong with the vintage bods who remove the
wrappers from ancient leaky paper capacitors, sorry condensers, and replace
with modern functional polypropylene ones covered with the original wrapper.
But safety matters are something else.

Indeed, some guys will happily pay for you to go to the trouble of
reusing the old condenser casing and carefully fitting new caps inside.
I did a WEM Copycat some time ago in such a fashion with those yellow
and red caps and I have a fair stock of the old Mullard brown blobs.
When rewiring say, a Stratocaster the customer wants the same varnished
cotton covered black and white wire as original. I've even heard of
someone making dummy replica 'death caps'for those US ampss!

It`s important to some people that it looks as original as possible
inside and out.

However. as you say, safety is paramount.

RonUK