possible power transformer solution for champ type build

[theroundhousernr]

Hello all..  New to this forum and amp building. Ive always been into electronics and gizmo and building circuits but never anything tube related.. I have been reading a bunch and studying up and have decided to take the plunge. Mainly cuz i need a smaller practice amp and i enjoy building.. SO anyway... I have found a neat old chassis at a local fleamarket. It was some type of DC generator/ AC power supply. It wasnt used for anything audio. The tubes used where a 5651, 6AU6, 6A57 and a 5U4 rectifier. I bought it because i liked the thought of recycling older parts and it has a neat look to it.

  Now to the question at hand. I will be sticking to the 5F1 schematic fairly religiously being this is my first build and starting out. So looking at the schematic i need a transformer that provides my high voltage secondary at 650 volts with center tap for ground and 5 volt winding to feed the 5y3 rectifier to provide my roughly 325 plate voltage. Also a 6.3 volt winding for filaments to the pre and output tubes (12ax7 and 6v6 ) . In effort to preserve most of the chassis parts from the previous chassis i would love to use the power transformer.. Its big and heavy duty and has a great look to the rest of the chassis...but i will not sacrifise looks over performance.

  So my issue is as so....original transformer outputs are....800V secondary with center tap, a 370V output and a 5.4V output. Hidden on the bottom side of the chassis is a second transformer wired in parallel to the mains putting out about 7.5 volts which i believe supplied the heaters in the tubes. All these measurements have been taking with no load on the transformer.. So being everything in unregulated so to speak i realise transformer tend to read much higher voltages...

  SO big question is.. are these readings to high on the secondary with center tap for my amp build?? Ive seen readings from fender champ power transformer reading as high as 750 with no load. But this baby is rather large and of a much higher amp reading. Im afraid the small load of a champ circuit wont pull it into an exceptable range. Can i alter transistors to fix that???doubt it since the secondary is wired straight to the 5y3..
  Second question...is using a second tranformer to provide my filament and heater current asking for noise and other issues i cant see present due to my lack of knowledge in this world???
 
  If this is just a bad idea...i will just opt for purchasing the correct power transformer beings that i have to order the output transformer anyway....sorry for the long post.. I hope i was clear... Thanks in advanced for any help!!  Kyle
 

[shooter]

can you re-check the 6A57, could it be 6AS7?
from tube data can't find 6A57, but 6AS7, 6au6, 5651, they all seem to like ~250 - 300vdc.

have you tore it apart?

[sluckey]

...i will just opt for purchasing the correct power transformer beings that i have to order the output transformer anyway

That's a good idea.

[theroundhousernr]

There was not much to see....there where big huge caps covering most of the tube sockets and wiring and there was no board...Everything was just soldered to the tube sockets and a few gang terminals. I did however leave all the power leads wired to the tube sockets... but all the OLD caps and resistors where removed... Please excuse my grammar error earllier in asking if transistor values could be changed... i meant resistors....And yes 6AS7 is the correct number.. The previous builder had labeled everything very well... the 350 leads off the transformer where wired right to outside terminals and labeled as such... and then there where DC terminals on the outside of the chassis... there was a POT for what i beleive was to adjust DC voltage....I did however take picture before i gutted the chassis..

[theroundhousernr]

https://ibb.co/iQAKRH   picture of chassis

[theroundhousernr]

https://ibb.co/cNJZtx   Picture of underneath

[ALBATROS1234]

definitely save the other power transformer for your next build. it will be simpler to build something if you just order all the right parts off of a list like hoffman has. it seems usually the pt has all of the windings included in one but i cant see 2 separate transformers creating extra noise. i am new as well but a bit unconventional in that i just got some parts and pieces together and experimented until i got something that i liked. at first i built a overdrive with back to back step down xfrmrs and a separate 6 volt wall wart and my first amp started off with a control xfrmr for high voltage with a bridge rectifier and 2 wall warts for heaters. its was and is very quiet even though now i am down to 2 transformers. i ended up with something champ like except different tube types and i have a tone knob and 2 volumes pre and post the second triode stage. these guys are great they helped me with my design issues.

[PRR]

It is an adjustable 100V-400V ~~200mA DC power supply.

_I_ think it is quite valuable as-is (fixed), as a bench supply for general amplifier work.

That PT may be plenty for a 50 Watt Marshall; way over-size for a Champ.

[theroundhousernr]

Sounds like everyone is saying order the new power transformer... I do like to preserve things however this is not factory made.. It most likely home brew bench power supply... The wiring is kinda shotty and there is no mains fuse. The chassis has two extra cut outs for tubes. It almost seems like it was for something else or part of a kit of sorts.. So I guess I will just save the power transformer for something else and order a new one. Glad to have a little insight. I do believe I can make this setup work but again since this is my first build and I would like to use it regularly. I want it right.

[ALBATROS1234]

i would take some quick pictures of the wiring in case you ever want to study haow things were wired on the existing circuit.