Newbie's power supply woes

[ScottTracy]

Hi there everyone, I really hope I'm not wasting anyone's time with this one. In fact I was determined to work it out on my own rather than trouble you but I don't have anyone else to consult so:

basically, this is my first build and although I can find 2 or 3 designs that i'm confidant I could build, I can never find suitable transformers for the projects because I live in the uk. For example, I wanted to build Mikael's KT88 SE and use this power supply but I cant find a transformer with a 5v winding rated at 3A only ones rated at 2A. and so on.

So finally I have settled on building the SE amp which can be found here but I cant find a 230/290 transformer with a high enough current rating and so I was wondering if I could use this 350-0-350 transformer with a GZ34 rectifier, but i dont know how to work out the voltage lost across the valve (and thus the output HT+ voltage). I'm guessing that the GZ34 substituted in place of the bridge rectifiers, I should get about 380-370v but i dont know how to calculate it for certain and if it was 5-10V high, would it do any damage?

Thanks for bearing with me. One last thing, if I substituted in a Sowter output transformer meant for pp/ul with a tap at 43% in place of the Lundahls would I have to make any alterations/ is it do-able at all?

Thanks in advance, this has been driving me crazy and dont pull your punches if I'm making some huge errors here.

[Tony_T]

Hi

With this mains transformer, GZ34 and similar choke (RDC 200Ohm) you should get about 380-390V.
5-10V high wount do any damage, can be dropped with some series resistance. Say one RC stage after LC, if needed.

As for output transformer, you can`t use PP transformer in SE amp.

[Zen Mod]

http://www.duncanamps.com/


software-PSU designer........

[ScottTracy]

great. thanks a lot guys.

[Eli Duttman]

Scott,

Your being located in the UK is NOT a problem. AAMOF, it may be a blessing. Sowter, an old established English firm, can wind just about any power trafo you care to mention and the cost will not be outrageous.

Sowter

BTW, Sowter is not the only UK magnetics builder. Stevens and Billington is another resource.

[Sherman]

Originally posted by ScottTracy
... I wanted to build Mikael's KT88 SE and use this power supply but I cant find a transformer with a 5v winding rated at 3A only ones rated at 2A. and so on.

...

That PS was the one I designed for my build of Mikael's amp. I wouldn't worry about exact matching. If the 3A winding isn't available then look for a different tube rectifier that takes only 2A for the heater. (Or use SS rectification and use no 5V secondary at all.)

As mentioned below go to Duncan Amps and download the PSU Designer and TDSL personal edition. With those two programs you can easily find different tubes and design a power supply to fit your amp.

Good luck and have fun!