musicman HD150

[goosonique]

nice amp but mines a sad story at the moment ..... The power transformer died after the factory filter caps exploded
did the RG's tube amp debug pages ...and yes its dead
(thanks RG .. )

Tried looking for a replacement but only a 110v primary type is available at mojotone...its 240v here !!

I found the schematic here
and i have got a kind soul to wind me a new replacement but he needs the secondry output voltages and i can't seem to figure it out .... 

Yes the schematic does show the dc required but can't figure out the actuall secondry output and hope you fellas can make my day..... 

Thanks Heaps !!!!

[Mark Hammer]

You should probably refer your question to the Music Electronics Forum (formerly AMPAGE).  It is to amps what this place is to stompboxes.  You'll get smart replies here,to be sure, but you'll get a lot more of them over there, and possibly some local contacts as well.

[brett]

Hi
The AC output required to produce a certain DC voltage is fairly easy to work out.

First, consider that the rectifier turns the sine wave into a series of bumps (any web page about full wave rectifiers will show this).
If the filtering is really, really good, then the DC will be nearly 100% of the peak of the bumps, but usually, it will be more like 95% of that.
The peak of a sine bump is 1.4 times the RMS voltage (ie the usual volts quoted for AC).
(And if you are really fussy, or working with low voltages, you need to allow for the 1.5V lost in a full-wave rectifier)

So, the formula is:

DCout = (ACin - 1.5) x 1.4 x 0.95

e.g. 350 V AC gives 466 V DC.

Rearranging the equation above:

ACin = DCout/1.4/0.95 + 1.5

e.g. 500 V DCout = 377 V ACin

Generally, you should aim high for DC output voltages (5 to 10% over), as they are easily trimmed with a little resistance (and this extra resistance is often said to improve the "feel" of the amp").  However, some MusicMan amps run EL34s at 700V DC.  This is very very high, so please don't use a final B+ voltage exceeding 700V.  EL34s are happier around 500 to 600V.
cheers

[goosonique]

awesome thanks Mark.... i will hop over to ampage and do a search first ....

Hey Brett ...thanks heaps ... feels like back to school  I have learnt something new today....that formula is what i needed!

Just cant wait to have my Mman up runnuin  ....