[[email protected]]

does anyone know where to find a replacement output transformer for th
mesa boogie mark iv, what the frequency response is, or how to
calculate it?

[Phil Allison]

wrote in message
ups.com...

** Desperate Groper Alert


does anyone know where to find a replacement output transformer for th
mesa boogie mark iv,


** It is a custom made part and MUST come from Boogie - ie Mesa Engineering.

The only alternative is to get the old one rewound by an expert.


what the frequency response is, or how to
calculate it?


** It is a custom designed transformer - you boob.

http://www.tubefreak.com/mk4-4.gif




........ Phil

[[email protected]]

On Mar 7, 7:05 am, François Yves Le Gal wrote:
On 6 Mar 2007 18:29:48 -0800, wrote:

does anyone know where to find a replacement output transformer for th
mesa boogie mark iv

Ask Mesa or any Mesa service station, or get some third party iron from
Mercury or TAD.

BTW, there's usually a very good reason why an output tranny has fried or
shorted...

http://www.amplifier.cd/Tutorial/Fre...y_Response.htm

[Phil Allison]

"François Yves Le Gal"

does anyone know where to find a replacement output transformer for th
mesa boogie mark iv

Ask Mesa or any Mesa service station, or get some third party iron from
Mercury or TAD.


** It is a custom designed transformer - you wog boob.

http://www.tubefreak.com/mk4-4.gif

See the primary side PLATE trappings for the pairs of tubes.




........ Phil

[Jim]

wrote:

does anyone know where to find a replacement output transformer for th
mesa boogie mark iv, what the frequency response is, or how to
calculate it?


The problem is the Simu-class setup, and the taps on the primary.
You're locked into an oddball transformer. I'd grit my teeth and call
Mesa. I'd also check Mercury Magnetics, but their often more money than
OEM. But be SURE you really need the OPT before buying, it ain't gonna
be cheap. How did it get fried?

[Phil Allison]

"François Yves Le Gal"

"Phil Allison"


** It is a custom designed transformer - you wog boob.


See the primary side PLATE trappings for the pairs of tubes.

See the schemo for the TAD version :


** OK - you wog ****head.

Next time you want to refer to a parts supplier - use their **actual
name** !!!!!

Not some invented, mysterious bloody acronym.

**** off.



...... Phil

[Phil Allison]

"François Yves Le Gal"


Next time you want to refer to a parts supplier - use their **actual
name** !!!!!

What part of TAD is unclear Bozo?



** All of it -

you stinking, ASD ****ed, pile of frog **** .




...... Phil

[Jim]

Bret Ludwig wrote:

On Mar 7, 3:22 pm, Jim wrote:

wrote:

does anyone know where to find a replacement output transformer for th
mesa boogie mark iv, what the frequency response is, or how to
calculate it?

The problem is the Simu-class setup, and the taps on the primary.
You're locked into an oddball transformer. I'd grit my teeth and call
Mesa. I'd also check Mercury Magnetics, but their often more money than
OEM. But be SURE you really need the OPT before buying, it ain't gonna
be cheap. How did it get fried?


It's simply a generic Schumacher transformer with taps, like screen
taps,

Yeah, and

at different percentage of the plate to center tap.

^^^ BINGO, that's what I was talking about.

If you get a new one or have access to another SimulClass, do us a
favor. Tell us what the taps are at. Put a known 1 kHz audio voltage
at the secondary and tell us the AC reeading of the five primary
windings (with the center tap at ground.)

[Phread]

"Bret Ludwig" wrote in message ups.com...
On Mar 7, 3:22 pm, Jim wrote:
wrote:
does anyone know where to find a replacement output transformer for th
mesa boogie mark iv, what the frequency response is, or how to
calculate it?

The problem is the Simu-class setup, and the taps on the primary.
You're locked into an oddball transformer. I'd grit my teeth and call
Mesa. I'd also check Mercury Magnetics, but their often more money than
OEM. But be SURE you really need the OPT before buying, it ain't gonna
be cheap. How did it get fried?

It's simply a generic Schumacher transformer with taps, like screen
taps, at different percentage of the plate to center tap.

If you get a new one or have access to another SimulClass, do us a
favor. Tell us what the taps are at. Put a known 1 kHz audio voltage
at the secondary and tell us the AC reeading of the five primary
windings (with the center tap at ground.)

I just happened to have a Mk IV on the bench so I took some measurements
this morning which seem to indicate that in fact it's a conventional xfmr with 2
leads at each end, rather than separate taps for the inner 2 tubes. With 1 VRMS
on the 8 ohm secondary, the voltage at all 4 plate leads (relative to the center
tap) was exactly 7.087 VRMS. The DC resistance between the leads on each
end of the primary was 0.02 ohms, about right for a few inches of lead wire but
not for any significant fraction of the primary winding, which measured 35.5 ohms
from CT to either plate lead on one half and 44.6 ohms on the other.

Perhaps the OP could open up the blown xfmr and see if the wires are actually
connected to 5 points on the primary or only 3. I'm thinking there will be only
3.

There was no sign the tranny I measured was anything but original or that it had
ever been replaced, and it had the right markings for an original xfmr - 562004R-1,
Mesa Eng, Simul-Class, EIA 606-230.

Fred

[Phil Allison]

"Phread"

I just happened to have a Mk IV on the bench so I took some measurements
this morning which seem to indicate that in fact it's a conventional xfmr
with 2
leads at each end, rather than separate taps for the inner 2 tubes. With
1 VRMS
on the 8 ohm secondary, the voltage at all 4 plate leads (relative to the
center
tap) was exactly 7.087 VRMS. The DC resistance between the leads on each
end of the primary was 0.02 ohms, about right for a few inches of lead
wire but
not for any significant fraction of the primary winding, which measured
35.5 ohms
from CT to either plate lead on one half and 44.6 ohms on the other.

Perhaps the OP could open up the blown xfmr and see if the wires are
actually
connected to 5 points on the primary or only 3. I'm thinking there will
be only
3.


** I have seen the five wire primary version many times.


There was no sign the tranny I measured was anything but original or that
it had
ever been replaced, and it had the right markings for an original xfmr -
562004R-1,
Mesa Eng, Simul-Class, EIA 606-230.


** Mesa have two versions of the output stage, one using mixed EL34 and 6L6
tubes and the other with all 6L6.

I posted schem this earlier in the thread.

http://www.tubefreak.com/mk4-4.gif

So maybe when they ran out of five wire OTs one day they just used what they
had.

Expect *anything* for the " Messy Bodgie " company.



........ Phil

[Phread]

"Phil Allison" wrote in message ...

"Phread"

I just happened to have a Mk IV on the bench so I took some measurements
this morning which seem to indicate that in fact it's a conventional xfmr with 2
leads at each end, rather than separate taps for the inner 2 tubes. With 1 VRMS
on the 8 ohm secondary, the voltage at all 4 plate leads (relative to the center
tap) was exactly 7.087 VRMS. The DC resistance between the leads on each
end of the primary was 0.02 ohms, about right for a few inches of lead wire but
not for any significant fraction of the primary winding, which measured 35.5 ohms
from CT to either plate lead on one half and 44.6 ohms on the other.

Perhaps the OP could open up the blown xfmr and see if the wires are actually
connected to 5 points on the primary or only 3. I'm thinking there will be only
3.


** I have seen the five wire primary version many times.

This one had all 5 wires, it just measured like a standard 3 wire
xfmr with 2 extra wires tacked on to the ends. I've never seen a
Mesa Simul-Class that didn't have 5 wires, but I've never had a
reason to actually measure one of their trannies until Bret
suggested it in this thread. I've always assumed they were
similar to a UL xfmr with the taps moved out closer to the ends,
but I see once again that assuming is just another word for
guessing, or maybe hoping. Perhaps their xfmrs had taps at one
time but the bean counters eventually nixed it as too costly.

There was no sign the tranny I measured was anything but original or that it had
ever been replaced, and it had the right markings for an original xfmr - 562004R-1,
Mesa Eng, Simul-Class, EIA 606-230.


** Mesa have two versions of the output stage, one using mixed EL34 and 6L6 tubes and the other with all 6L6.

Yeah, I've seen them both ways. This one was fitted with 4 6L6's,
all Mesa Boogie branded. My schematic, like yours, says EL34 or
6L6 for V6 & V7. Like most of the Mk 4's I've worked on, the 2.2K
grid stop resistors for V6 & V7 weren't there, which means it's at
least a few years old - Mesa figured out several years ago that
leaving those 2 resistors out could cause loud pops or shrieks at
turn on in some amps when all 4 tubes were on, because V6 & V7
could break into oscillation. I put the missing resistors back into
the amp. Long live the bean counters! I've earned a lot of money
fixing their stupid mistakes!

I posted schem this earlier in the thread.

http://www.tubefreak.com/mk4-4.gif

So maybe when they ran out of five wire OTs one day they just used what they had.

Expect *anything* for the " Messy Bodgie " company.

What's that song say? Don't try to lay no Boogie Woogie on the
King of Rock & Roll! ;-)

Fred


....... Phil

[Phil Allison]

"Phread"
"Phil Allison"


** I have seen the five wire primary version many times.

This one had all 5 wires, it just measured like a standard 3 wire
xfmr with 2 extra wires tacked on to the ends. I've never seen a
Mesa Simul-Class that didn't have 5 wires, but I've never had a
reason to actually measure one of their trannies until Bret
suggested it in this thread. I've always assumed they were
similar to a UL xfmr with the taps moved out closer to the ends,
but I see once again that assuming is just another word for
guessing, or maybe hoping. Perhaps their xfmrs had taps at one
time but the bean counters eventually nixed it as too costly.


** That is very interesting.

The next example I see will have its OT checked carefully.

What a devious bunch of cretins Mesa are.


As Sylvester the Cat famously said, many times :


" I hate those Mesas - to - Pieces ...... "




......... Phil