Marshall JCM 2000, 1998

[N_Cook]

Blown primary of the mains Tx, isolated removed from chassis, draws 1.2 amp
at 20V variac "mains" and temp climbs 20 deg C in 4 minutes or so.
Secondaries measure l27V, 16.3V and 2V so that side presumably ok.
DC of primaries measure 1.2R and 2.2R, would they use 2 bifilar primary
windings where stressed midpoint would show half way short and half measured
ohms?. I will poke around in the winding/ try delaminating out of curiosity
but
stock fault/ batch fault ? Other than "marinating" in paint stripper , any
tips on delaminating ?
Are replacements available from Marshall ? or a grey market source UK ? or
anyone use 2 or 3 separate Tx ? Googling Tx model
Dagnall, TXMA 00061, D2105
only shows up suspiciously low priced dollar quotes

 

[Meat Plow]

Blown primary of the mains Tx, isolated removed from chassis, draws 1.2
amp at 20V variac "mains" and temp climbs 20 deg C in 4 minutes or so.
Secondaries measure l27V, 16.3V and 2V so that side presumably ok. DC of
primaries measure 1.2R and 2.2R, would they use 2 bifilar primary
windings where stressed midpoint would show half way short and half
measured ohms?. I will poke around in the winding/ try delaminating out
of curiosity but
stock fault/ batch fault ? Other than "marinating" in paint stripper ,
any tips on delaminating ?
Are replacements available from Marshall ? or a grey market source UK ?
or anyone use 2 or 3 separate Tx ? Googling Tx model Dagnall, TXMA
00061, D2105
only shows up suspiciously low priced dollar quotes

http://www.mercurymagnetics.com/pages/mainframe.htm

Should ship internationally.

 

[N_Cook]

We get parts direct from Marshall. Used to be a Marshall dealer, but we are
not any more, and they still supply us with parts ok, so it must not be a
requirement. It may be that you have to be a 'legitimate' business though,
and not just 'Joe Punter'.

Arfa

Any ball-park idea of cost for a Marshall replacement ?

 

[N_Cook]

At least its the outer 120V primary at fault and a split bobbin so once the
laminations are apart , easy to inspect. Tomorrow I will try a 125W iron
concentrating on the central sliver of the first "E". Laid thin ptfe sheet
heat insulation under the other 3 slivers. What will be the softening
temperature of the lacquer and any guesses as to time of heat application at
the exposed end only ? At least I can monitor the other end with a
pyrommeter.

 

[N_Cook]

seconf attempt

Ball park between £20 and £30 inc P&P and VAT.

Did you leave out some zeros? 200 to 300 GBP
eg
http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_CLASSIC_AMPS_15.html

 

[Phil Allison]

"Nutcase Kook"

Did you leave out some zeros? 200 to 300 GBP

** The Dagnall brand trannies that are fitted to modern Marshalls are all
made in India or Shi Lanka by starving children.

The design is way under sized for the job and quality is non existent.

Spares are cheap, IME.

Shame the fucking amps are not.





...... Phil

 

[N_Cook]

Normal single filament winding. Normal failure mode , for slapdash wound Tx
these days. Slipped turn at one end of a layer dropping into a lower layer,
then presumably chaffing of lacquer to marginally spot weld. Not at all
obvious "weld" point , about 80 turns from lead out of outer primary. 195
turns in all of .75mm wire for one 120V primary. Not a problem here as 240 V
use, but would be for this Tx used in USA . There is tape covering the inner
primary but not extended at the leadout point of the inner primary so first
turn of the outer primary directly crosses that point so a full short is
very likely there with a bit of normal in service vibration/ chaffing. For
240V use those 2 points are at near enough same mid-mains potential (2 tails
to options bridging point on pcb)
At least I now know how to delaminate the E/I iron laminations.

 

[Phil Allison]

"Nutcase Kook"

Normal single filament winding. Normal failure mode , for slapdash wound
Tx
these days. Slipped turn at one end of a layer dropping into a lower
layer,
then presumably chaffing of lacquer to marginally spot weld.

Not at all
obvious "weld" point , about 80 turns from lead out of outer primary. 195
turns in all of .75mm wire for one 120V primary. Not a problem here as 240
V
use, but would be for this Tx used in USA . There is tape covering the
inner
primary but not extended at the leadout point of the inner primary so
first
turn of the outer primary directly crosses that point so a full short is
very likely there with a bit of normal in service vibration/ chaffing.

** The turns wound on that transformer do no move or chaff - you wanker.

Those Dagnall power transformers ( TMXA00061 etc) are made with low temp
grade enamel coating the copper and the tranny is under sized for the job it
has to do - not to mention working in a very high ambient temp from the heat
of the output valves.

As a result the windings run DAMN hot, the enamel gets soft and when two
soft spots meet under pressure you can get a short.

I have THREE dead ( internally shorted) examples of the exact same tranny
sitting here right now.


..... Phil

 

[N_Cook]

Marshall replacement £46 , same duff construction as this one?

 

[Phil Allison]

"N_Cook"

Marshall replacement £46 , same duff construction as this one?

** Of course.

Only way to fix the problem is to find someone willing to rewind the
original transformer with high temp enamel wire - ie 180C rate instead of
the 120C rated stuff used by Dagnall.

Or you could fit a small fan blowing on the tranny....


...... Phil

 

[Phil Allison]

"Gareth Magennis"
"Phil Allison"

I'll go with Arfa's suggestion.

** Makes you as big a fucking halfwit as he is.

Pay the £46 and when it breaks in 13 years time,

** HUH ???

What sort of madness makes do you think the problem has a 13 year delay
built in ??????

That POS tranny can fail in the first few hours of use !!!

Only has to overheat enough to soften the enamel on the wire - and overheat
it surely will cos it is not correctly sized ( in terms of VA rating) for
the job it has to do.



...... Phil

 

[Phil Allison]

"Arfa Daily"


** Please come to Sydney - Arfa.

Just buy a one way ticket, cos that is all you will need.

Go straight to Circular Quay from Mascot airport and then into any pub with
your stupid, whiny pommy voice and tell everyone there all your brilliant
thoughts.

The sharks in Sydney harbour will be picking your bones by nightfall.



...... Phil

 

[N_Cook]

I would expect it to probably be a ringer for what was already in there. If
the amp is really from 1998, then duff construction or not, it ain't done
bad, and if the new one does another 13 years, it's not going to come back
on you, is it ? And, if in the intervening 13 years since it was made,
Marshall have had a lot of them fail, then maybe they've taken this up with
Dagnell, and got them to improve the situation ? I would stop agonising over
it, and just stick the new one in, and write out the hundred quid bill for
the owner ...

Arfa

What is the point of CE "compliance" testing etc if 2 layers of lacquer to
resist 120V av . At one time, before CE marking, all these Tx tails had
extra sleeving over them to avoid this problem.

 

[Phil Allison]

"Gareth Magennis"

That may be more of a problem in the heat of Shark Infested Sydney than
the cold wet miserable UK,

** So it is always " cold wet and miserable " INSIDE a venue in summer
plus INSIDE a Marshall valve amp playing " Death Metal " riffs to hundreds
of head bangers in the UK - is it ??

God, what a fuckwit you are.



** The easy and engineering wise final solution is the re-wind I suggested.

**** head.



..... Phil

 

[N_Cook]

What indeed? agreed. Unfortunately, that's just the world that we live in
now. Long ago, I gave up trying to change the situation, got over it, and
just got on with making a living ...

Put the new tranny in, write up the bill, and move on to the next one

Arfa

For balance I got a quote from proper tx winders Majestic , just down the
road
http://www.transformers.uk.com/brochure.pdf
for a one off , custom/semicustom build from scratch , to specified V & A of
the 3 secondaries. Somewhere between 50 and 70 GBP plus VAT plus carriage,
about 2 week turn around

 

[Phil Allison]

"Nutcase Kook "

For balance I got a quote from proper tx winders Majestic , just down the
road
http://www.transformers.uk.com/brochure.pdf
for a one off , custom/semicustom build from scratch , to specified V & A
of
the 3 secondaries. Somewhere between 50 and 70 GBP plus VAT plus carriage,
about 2 week turn around

** That is a very reasonable price.

But did you ask them to make a new tranny with the exact same stack size and
through chassis design as the Dagnall ones ??

Were they offering you a custom toroidal tranny by any chance??


...... Phil

 

[Phil Allison]

"Gareth Magennis is an utter ASS "

Just gone through my database.

** Go shove you stupid fucking database up you stupid fat arse !!

Engineering facts are F A C T S !!

You pathetic, pommy DUMBASS !!



..... Phil

 

[Phil Allison]

"Gareth Magennis"


** Bullshit stats YOU INVENTED are not engineering facts !!

YOU GOD ALMIGHTY KNOW NOTHING POMMY ****

 

[William Sommerwerck]

Or perhaps he'll get his head stomped on by an irate kangaroo...

Disembowelment from a kick is more likely.

Herbivores are more dangerous than carnivores.

 

[N_Cook]

Added a 12V 1.5 inch fan at the Tx. Using the unused heater tag for main
mount of the fan to solder a solder tag then that bolted to the fan.
Setting fan at 20 degrees to the horizontal and cutting and fitting a
shroud from that red impregnated cardboard stuff to direct the flow into one
side , up, over top and back out the other side between windings and bobbin.
As secondary side gets hotter than primary , fan positioned mainly on that
side
Air flow checked using a joss stick. Perhaps next time using some DC from
the amp rather than bridge rect and cap off the heater supply as light
current drops in the diodes bring it down to less than 9V . Retained the
template for the shroud for the next one of these to attend to.