Transformer locations

[genewiseman]

I have been working on a 5f1 champ clone that I built a long time ago. I am making a new chassis and trying to lay everything out just like Fender did. When I originally built the amp I layed it out all wrong and I would like to get all the hum out of it. The only thing that I haven't been able to find is a view of the power and output transformers as they are installed on the chassis. I have a good idea of what will work but I would like to see just how Fender did it.
Thanks a lot,
Gene

[Jazz P Bass]

Some good points to consider here: How to Layout and Build a Guitar Amplifier Chassis - GuitarKitBuilder

[DRH1958]

I found an original Fender layout drawing and a Champ clone kit which is consistent with the drawing. Obviously, the two larger holes close to the edge are the OT. On Fender's drawing, the OT holes are where pin 3 of the 6V6 and the speaker jack are. The OT lengthwise sits perpendicular to the lenghth of the chassis.

[guitician]

Here's a pic of a tweed champ chassis...

[überfuzz]

... I would like to get all the hum out of it...

Unfortunately you can't blame al hum on the topology. For instance, 12AX7 filament wiring is actually quite a challenge when it comes to hum free wiring (there is similar tubes with better pin out if you're really digging deep into hum less).

[Enzo]

The transformers are probably down the list a good ways on the hum chart.

Note in your schematic for the 5F1, one side of the heaters is grounded, rewire that for twisted pairs of wires, and then make a virtual center tap.

Those tiny 8uf and 16uf filter caps are marginal, beef those up some.

Look at the B+, the first filter goes right to the output transformer. That might be OK in a push pull, but by its nature, you will have a hard time keeping hum from that out of the power tube. Fender even issued a service bulletin on Champs telling us single ended amps like that have a natural level of hum, and don't try to"fix" it under warranty, it is normal.

Look at the 5C1, see there are two stages of filtration by the time we get to the output transformer. The 5E1 is even better, it adds a choke, so you have a CLC filter before the output tranny. Those two will have superior hum rejection in the power stage.

Once you have a center tap, virtual or real, on the heater supply, then grounding that helps, but connecting the center tap to the cathode of teh powr tube will help even more. That will elevate the preamp tube heaters.

There are a zillion sources of hum, and each one has its own countermeasures. Adding filter caps will not remove ground hum, and moving the transformers will have no effect on power supply ripple, for example.

[bluto]

One trick I used on a scratch built amp was to mount the OT on the underside of the chassis, from what I've read this was common on hifi tube amps back in the day....also did this on a Gibson BR6 I converted from field core to a regular speaker (FWIW the BR6 was a train wreck when I got it, did NOT hack up a good example)

[Chuck H]

I built a little single ended amp for a guy and did the heaters exactly as Enzo described. Including referencing the filaments false CT to the 6V6 cathode. I had very good results. As in leaning my ear close to the cabinet to be sure it was on! This amp knew the words. No humming.

[genewiseman]

Thanks for all the help. I am building a new chassis because I built the first one with the preamp tube right next to the power transformer. I just figured that I would play it safe and lay everything out just like the original. I think I can get it pretty quiet just by laying it out in a already proven manner.
Thanks again,
Gene