Fender Champ 5C1 Transformer Specs help for Newbie

[Guitam]

Hi,

I'm hoping someone can help me with some information.

I've been doing some minor servicing on my amps and thinking about building one for a while. The other night when I pulled the chassis out of my 54 Champ to replace a burnt resistor - I had that "I can build one of these" moment! So a Champ 5C1 circuit it is.

Now my question is, what are the specs I should look for in both the power and output transformers?

Any help would be much appreciated.

Mat

[jimipage]

I'd suggest using a Hammond 270CAX for the PT and a Hammond 125CSE (or even the DSE) for the OT. You'd also have enough juice there to use two 6v6's in parallel. You can check out the specs here:
http://www.tubesandmore.com/

and for good reference:
http://www.angela.com/
go to the "How To Section" and read about the Angela single-ended and Super single-ended amps. This should help answer a lot of questions you may have.
good luck!

[Manoteal]

I would think that you would need a power transformer that would supply at least 40 mA @ 300+ volts for the high voltage, 6V at about 1 amp for the filaments of the two audio tubes, and 5v @ 2 amps for the rectifier if you stick with a tube recto. Remember that there will be a voltage drop of 40-50 volts for the 5Y3 that is specified in the Fender schematic. So you would want a higher voltage to start with to allow for this drop and perhaps 350 @40 mA would be good for that use.
A 6V6 gives you about 5 watts single ended and the output transformer that would be closest to what you want would be a 7.5K- 8K ohm to voice coil @ 5 watts or larger. Use the higher value for 350 volts and the lower one for 300 volts. That should get you into the ball park. Use whatever output you want for your speaker, or get multiple taps for more flexibility.
If you want to get everything at once, check out-

http://store.triodestore.com/singleendedbundle.html

Hammond also has many options as well as other transformer builders.
Anyone had a good experience building one of these?


M

[Phil_S]

This should give you a pretty reliable idea of what you need:
http://www.mercurymagnetics.com/pages/mainframe.htm
Scroll down to the Champ section.

This is a single ended amp, meaning that the 6V6 is "on" all the time. A 6V6 requires about 40mA to operate, but the class A type circuit is rather inefficient. Therefore, it is wise to derate and buy something that can support more than the rating. I would look for something around 80mA, otherwise it will run quite hot (physically).

[harpo]

For the Champ PT you need 275-0-275 around 50mA rating with a 5V winding for the 5Y3 and 6.3V winding for the heaters. A Hammond 270BX would work or if you want a more "authentic" looking unit the Mojo Tweed Champ replacement unit would work well too.
I've used the MM OT and frankly, it is not worth the money IMHO. Again, if you want more authentic vintage clone performance the Mojo OT is a good choice especially for around $30. For "better/non-vintage" performance the Hammond 125CSE or 125DSE would be good choices.
Hope this helps,
John

[Alexo]

A 5C1 was my first scratch build, cool little amp...

Here's what I would have done differently:

I think I ordered a 300-0-300 or maybe even 325-0-325 PT, well where I live Hammonds put out about 12% over what they say, so I recently measured a "275" transformer and found it to put out something like 312 volts! SO I would suggest getting a 275-0-275 PT if you're getting a Hammond.

Also I would suggest getting a big beefy 125ESE output transformer, using a 10 watt cathode resistor, 2 or 5 watt grid resistor and at least a 50 volt rated cathode cap, tie pins 1 & 8 together on your 6V6 socket and you can drop in pretty much any tube you want - EL34, 6L6, 6V6, 5881, etc., I set mine up with a 5K:8 ohm setting on my OT and a switch to go to 2.5K:8 when I want to use an EL34. Oh yeah... you will also need a PT that can handle at least 100ma to do this.

A champ is an interesting first build, you'll get it going stock and then start checking out the voltages and get confused because these amps tend to run things beyond the limits stated on tube datasheets and such. Just check that your voltages match this layout and you should be good.

[Guitam]

Hi,

Thanks to everyone. Plenty of information there to get my head around. If anyone has any other thoughts on this I'd love to read them.

Cheers,

Mat