Anthon

Making my first transformer. (5f1 Champ OPT)
« on: June 09, 2019, 06:24:25 AM »
After couple of years making various Fender-style clones, cabs etc I finally decided to start making my own transformers.
My tube audio adventure started with a 5f1 Champ clone, so why not start with OPT for this small but legendary amp. It seems to be easy enough.
I'll post some questions and my progress in this thread.

I have this recipe from vaacumbrain.uk (CJ)




Step one: get all the parts. I will be ordering from ascocomponents. I've already contacted them, they are willing to sell me some sample for my prototype.
They don't seem to have El-50 and 12.7mm bobbin like described in the recipe, so I'll take El-48 and 16mm bobbin instead.
Lamination material would be 0.5mm non grain oriented steel.
2 gauges of copper wire: 24ga and 35ga.

Step two: building the transformer.
I have a CNC coil winder. I will start by winding 2988 turns of 35ga wire for the primary, then some isolation tape, then winding 69 turns of 25ga wire for the secondary, then isolation tape.
Strip the isolation from the enamelled wire ends, solder some thicker wire, use some shrink tube, then securing the wires with more isolation tape.

At this point the coil could be dipped in varnish (which one would you recommend?), but would it be okay to skip this step for the prototype, since it would be easier to recycle materials, if something is wrong?
Then put the lams inside and put the U clamp on.
Or should it be dipped in varnish after the transformer is fully assembled? Or maybe both?

That should be it.  Please correct me if I'm wrong.


Re: Making my first transformer. (5f1 Champ OPT)
« Reply #1 on: June 09, 2019, 08:11:20 AM »
I was recomended an aerosol based varnish called Ultimeg anti tracking  , comes in a few different varieties or colours.
Its very  easy to give a quick spray as the layers go down , that locks everything into place
You may want to dip and bake the entire finished transformer too for a tropicalised finish , that will make stripping it down a bigger job later of course .

Seeing as you have the CNC at your disposal , you might be able improve on the simple winding scheme, pri/sec bobbin layout .

Maybe as an exercise would it be worth asking a question , all things remaining the same , ie tube, current, voltage, matching impedence, core etc how would we go about improving the winding geometry to get better frequency response ?


Anthon

Re: Making my first transformer. (5f1 Champ OPT)
« Reply #2 on: June 09, 2019, 09:15:12 AM »
I was recomended an aerosol based varnish called Ultimeg anti tracking  , comes in a few different varieties or colours.
Its very  easy to give a quick spray as the layers go down , that locks everything into place
You may want to dip and bake the entire finished transformer too for a tropicalised finish , that will make stripping it down a bigger job later of course .

Seeing as you have the CNC at your disposal , you might be able improve on the simple winding scheme, pri/sec bobbin layout .

Maybe as an exercise would it be worth asking a question , all things remaining the same , ie tube, current, voltage, matching impedence, core etc how would we go about improving the winding geometry to get better frequency response ?

I guess I could spray varnish as the coil spins, but I don't want to ruin my new coilwinder  ;D
I know spray fumes can travel everywhere, and I don't think it will be good for the mechanisms inside.
I guess the lacquer has to be very thin, to go deep inside the coil.

About the improving the frequency response:
Well, to begin I just want to make a transformer that doesn't melt when I put it in my tube amp  :)
Besides, for a guitar amp FR is not that important. If this is how the original 5f1 OPT was made, then I don't see the reason to alter the design.
But I'll need a lot of transformers for my DIY, so improving the design will be a good exercise. I'll think about it, when I have a simple prototype that functions properly.

Re: Making my first transformer. (5f1 Champ OPT)
« Reply #3 on: June 15, 2019, 01:58:20 PM »
Any progress Anth?

I suppose the easiest thing to do would be to layer the secondary instead of just random wound , that in itself might give better performance , in the olden days sometimes tissue paper/varnish  was used between layers , not so much for insulation as much for spacing .

The nice thing about the spray laquer is its very thin and gets right between the windings easily and it dries quick , the stuff is about 30 euros a can so you'd want to be using it spareingly , for tiny transformers for audio ,you could simply dispense some product into a plastic cup and apply with a small paintbrush , no need to do it while the winder is in opperation  :D

Im due to order my machine next week , are you happy with the quality of everything you got ?
were instructions included or any details of the manufacturer ,or where spares could be found ?

It would be great if you could post a photo with the panel off the machine , from what I can tell it uses a three phase ac motor driven off a VFD as winding motor and stepper motors for the traverse mechanism .

Anthon

Re: Making my first transformer. (5f1 Champ OPT)
« Reply #4 on: June 28, 2019, 08:47:42 PM »
Here are some pictures of the machine.
I haven't tried making a coil yet, I've just ordered the laminations and other parts.

But there is really nothing bad about this machine, from my first impressions. Seems to have very decent build quality, really can't complain at this price point.






Re: Making my first transformer. (5f1 Champ OPT)
« Reply #5 on: June 29, 2019, 04:05:50 AM »
Very interesting 👍

CJ

Re: Making my first transformer. (5f1 Champ OPT)
« Reply #6 on: June 30, 2019, 02:10:07 AM »
you could try two flavors if you have enough parts,

one would be the original Tweed Champ which is random wound,  try about 15 to 20 turns per layer,

the other would be a Black Face Champ, which uses even layers and layer insulation,

then hook therm both up at he same time with a switch on the tube plates to see what is shakin,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


 

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