MESA BOOGIE BLOWN PT

[etarist]

Hello tube masters;

I am by far not part of your league but found this forum in search of help.

I have a Mesa 20/20 tube power amp with a blown
mains power transformer and wonder if it can be resurrected?
Mesa Boogie wants $300.- plus shipping for the original.
That's an impossible number for me.
The amp is only 1rack unit high,
so it's difficult to find a slim replacement transformer.
I wonder if it would be feasible to have the trans re-wound?

Here's a link to the amp shem.:
 http://music-electronics-forum.com/attachments/11767d1290877369-mesa-20-20-poweramp.pdf

Edcor offers some trans' that may work.
Would somebody please take a look which one may be closest in your opinion, also
concerning filament current and some advise on swapping it out with the old.

- I'm not so worried about it sticking out above the 1rack highth; it will be mounted in a rack)
- I'd prefer 240V input because I take it to Europe quite often and use a "step-up" here.

So here the list in the order of my preference:
1. http://www.edcorusa.com/p/746/xpwr144_120-240  (200mA/3.5A)
2. http://www.edcorusa.com/p/889/xpwr047_240  (120mA/2.5A)
3. http://www.edcorusa.com/p/644/xpwr051_120 (125mA/4A)


Thanks and happy thanksgiving y'all, Stephan

[stratele52]

You are absolutely shure power T is burn ? 

You are qualified to say that ?

[etarist]

Thanks for the quick reply, Stratele52!

The PT is scorched, swollen and smells=certainly burned.

[jjasilli]

Note that if the PT is blown, this may have been caused by some other circuit fault which is the real culprit.  If so, a new PT might fry too.  It's a good idea to test the circuitry with a bench poer supply or other PT temporarily; and monitor current draw for a quick shutdown if needed.  Finaly, in case a circuit problem is intermittent, you might install fuses on the PT secondaries.

[stratele52]

Thanks for the quick reply, Stratele52!

The PT is scorched, swollen and smells=certainly burned.

+1000 jjasmill

You did not mentionned if amp is working with this transformer ? Or you just smell it and switch OFF ? Fuse burn ? 
Test voltage at the PT output first. if voltage too low , disconnect PT from the circuit and test with no load.

Amp circuit / output tubes could be short

[PRR]

> The amp is only 1rack unit high

That's 1.75 inches.

None of those will fit because they are all 3.22" the short way.

Electrically, only the XPWR144-120/240 is likely to carry four EL84.

[stratele52]

Thanks for the quick reply, Stratele52!

The PT is scorched, swollen and smells=certainly burned.

NO. this could mean , it is dirty OR it work hard ( short inside amp ? ) or because too small iron and not enough vent.

You did not answer to my question ; Is the amp is working or not ?

[phsyconoodler]

And blown fuses can mean bad rectifier diodes,not necessarily bad PT.

 Swollen? How? Out the sides? Bad smells:burnt diodes,fuses and resistors all smell pretty bad.


" I love the smell of napalm in the morning"

[etarist]

Thank you PRR for looking at the shem and
helping me with the choice of a transformer.

Thanks everybody;
I see that I have to get it checked thru more
thoroughly and not just go with the first service-guy
I asked. The amp does not turn on,
blows fuse when mains switch flipped.

Thanks again all for helping me figuring out
what next step to take;
now I know that there is a transformer that
would work (I don't mind if it sticks out into the rack space above)

So much for now; I may poke into this thread again later
with an update.
Have a nice christmas season;

www.etarist.com

> The amp is only 1rack unit high

That's 1.75 inches.

None of those will fit because they are all 3.22" the short way.

Electrically, only the XPWR144-120/240 is likely to carry four EL84.

[birt]

you might want to look at a marshall 20/20. they are also EL84 and 1 rack unit. those PT's are available on various websites. i don't know how close schematic and voltages are so check that.

here's a link with a modification and a schematic for the mesa: http://www.scribd.com/doc/6690230/Mesa-Mod

on this schematic the PT part number is not clear but it is 561020. maybe you can get one from mesa.

[stratele52]

on this schematic the PT part number is not clear but it is 561020. maybe you can get one from mesa.

etarist write ; "  Mesa Boogie wants $300.- plus shipping for the original.
That's an impossible number for me.  "

[birt]

the marshall has a plate voltage of 410V (not indicated on the schematic, found this online, another source says 380V), the mesa 390V. i think this could work.

stratele52, there is more than one source for mesa transformers...

[stratele52]

stratele52, there is more than one source for mesa transformers...

+1

[etarist]

WOW, thanks all for the kind and continuous advice.
Actually I have "plexi50" on it now; so the thread continues here:

http://www.el34world.com/Forum/index.php?topic=14719.0

Thanks plexi50; funny to now meet you here :-)

[plexi50]

The world and this transformer is getting smaller by the minute*   

[etarist]

;-)