Making my first transformer. (5f1 Champ OPT)

[Anthon]

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.

 

[Tubetec]

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]

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.

 

[Tubetec]

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 

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]

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.

 

[rock soderstrom]

Very interesting

 

[CJ]

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,

 

[Whoops]

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.

Do you have the model and name of that machine?

thanks

 

[abbey road d enfer]

Seems to be one of these:
https://fr.aliexpress.com/item/1005...8-42&pdp_ext_f={"sku_id":"12000024452568675"}I must admit I don't really understand the different options, though...
Seems to be different types of wire tension control.

 

[warpie]

So they are like 1,900 euro?

 

[abbey road d enfer]

The basic model is about €800.

 

[Whoops]

Friend Moby sent me this link, it looks the same machine but selling for 400€:

https://www.ebay.de/itm/Micro-Compu...2349624.m46890.l49286&mkrid=707-127634-2357-0

 

[abbey road d enfer]

Good find! And shipping is cheap.

 

[Tubetec]

The brake is solenoid operated and bolts onto the main motor shaft , it simply holds position while the machine is stopped The tensioner seems like it worth having for best precision , they are also available seperately on ebay .
The 404 euro machine is indentical to mine , I payed around 525 euros if memory serves me correctly , do check if your liable for tax or import duty to prevent getting hit with surprise charges .

 

[Moby]

Friend Moby sent me this link, it looks the same machine but selling for 400€:

https://www.ebay.de/itm/Micro-Compu...2349624.m46890.l49286&mkrid=707-127634-2357-0

Yes, that machines are all more or less the same. But also, tax goes on top of that price because it's exported from the Swiss.
Edit:
I have one machine like that and I use it for the prototypes or some rewindings. It serves great for the value.

 

[abbey road d enfer]

Friend Moby sent me this link, it looks the same machine but selling for 400€:

Another possibility:
https://fr.aliexpress.com/item/3273...t_f={"sceneId":"3339","sku_id":"61500776424"}It's not CNC, but it has the automatic wire guide.
Shipping is more expensive than cost of machine...

 

[lukas]

...maybe from Schweiz CNC automatische Spule Winder große Drehmoment Winding Machine Draht für 0.03-1.2mm Draht | eBay

 

[abbey road d enfer]

The brake is solenoid operated and bolts onto the main motor shaft , it simply holds position while the machine is stopped The tensioner seems like it worth having for best precision , they are also available seperately on ebay .

What I can't figure is how the wire guide functions. Is it fixed and the bobbin-holder shaft moves laterally?

 

[Tubetec]

Hi Abbey,
The main winding shaft is fixed and directly coupled to the spindle motor .
The wire guide push rod mounts onto a ball screw , belt driven from a stepper motor with a pair of linear rail rods with bearing guides for support . Its not a closed loop stepper , but you can program it to return to zero periodically , then have it dial back in the offset or start point to help minimise compound errors or drift .
The machine I got doesnt have the brake , but does have the mounting plate and a socket on the board for the supply , as well as a brake on /off button on the control panel .

I did look at reviews of the NZ-2 winder which is same as NZ-160 only has a clockwork counter instead of electronic. More or less everybody said it was pig of a thing and wasnt capable of winding fine wires without constant breakages .

Hi Moby ,
Have you done any demo videos with the cnc machine ? be great to see .
Good to know its capable of fine results , you've carved yourself out a nice niche there with the mic transformers . Ive had my CNC a while already , but lifes complications meant I didnt make much progress on my designs.
Be interested also if you can recommend a good source for lams and bobbins in relatively small quantities.

 

[abbey road d enfer]

Hi Abbey,
The main winding shaft is fixed and directly coupled to the spindle motor .
The wire guide push rod mounts onto a ball screw , belt driven from a stepper motor with a pair of linear rail rods with bearing guides for support . Its not a closed loop stepper , but you can program it to return to zero periodically , then have it dial back in the offset or start point to help minimise compound errors or drift .

Thanks for the explanation; it makes sense, however I don't relate it to the pictures...
These machines are sold by many vendors; not one has thought of posting a video...