Fender Hot Rod DeVille Output Transformer Teardown

[CJ]

Thanks1 Happy New Year to you and everybody else!

 

[CJ]

it is hard to drill a hole dead center, so if you slot the mandrel, you can use threaded rod to adjust things
,

 

[dougsta]

look how close the primary center tap (red) is to the business end of one of the primaries,
which is another good reason to put the secondary leads on the back. you can put more distance between the primary leads also.

View attachment 87812

Nice work on the OT teardown, very few out there.
If you need to keep the leads all on one side due to the chassis, would an inch or 2 of heat shrink on all the leads in addition to the tape be ok?

Doug.

 

[CJ]

they have been doing leas all on one side for years, but lately i have noticed that sometimes things are getting sketch, the pressboard with the staples is the way to go, like they did back when.

vinylglass sleaving works pretty good, high voltage, good for about 5 KV. and more puncture resistant, they call it by different names depending on who makes it, kind of a rubberized fiberglass mesh,

if you are careful you really do not need any extra insulation, just make sure your anchors are good , and a good varnish bake session does not hurt either.

 

[soapfoot]

Very interesting to follow this--

Is your goal to make it sound exactly like the original, or do you expect it to be improved?

 

[dougsta]

they have been doing leas all on one side for years, but lately i have noticed that sometimes things are getting sketch, the pressboard with the staples is the way to go, like they did back when.

vinylglass sleaving works pretty good, high voltage, good for about 5 KV. and more puncture resistant, they call it by different names depending on who makes it, kind of a rubberized fiberglass mesh,

if you are careful you really do not need any extra insulation, just make sure your anchors are good , and a good varnish bake session does not hurt either.

View attachment 87955

Yes, reinforced is a better idea, heat shrink can easily get solder spikes breaking through.

I've had good results rewinding 100v audio line transformers and reusing the terminals for small 6V6 or EL84 pp amps.

 

[CJ]

done rewinding this guy, used a bifilar wind for the 4 ohm secondary 68 turn wind instead of doing two winds and connecting in parallel,

had a mistake on the print, sec turns s/b 28 on the top wind, not 34, so P-P Z goes to 4K which is more typical for Fender for a pair of 6L6GC's.

and we attached a build chart which has outside dimensions of the coil as you wind. you really have to smash the arc out of the heavy #21 secondary layers to get everything to fit, that wire really ants to bow out and cause problems. i bet they had a wooden clamp for squeezing those layers at the factory. but you have to be careful not to damage the small primary wiry layers.
winding those speaker layers really puts a lot of torque on the coil, so the primary insulation has to be taped down tight. some folks use super glue to minimize leakage inductance by lessening tape volume. I will nuke the other print.

 

[CJ]

and the build chart which is used to keep an eye on the overall dimensions of the coil as you wind.
numbers are loose in tolerance as measuring is never exact due to varnish buildup and operator error.

 

[mjrippe]

@CJ - You are a MONSTER!

 

[SwedishWings]

and the build chart which is used to keep an eye on the overall dimensions of the coil as you wind.
numbers are loose in tolerance as measuring is never exact due to varnish buildup and operator error.

View attachment 88033

Hope I don't get burned to ashes for necroposting...

Thanks a million for all the information!

With regards to insulation, did they use interlayer insulation or just interwinding insulation?

 

[CJ]

yes, layer insl 0.003" Kraft Paper (brown paper they wrap your steaks in) transformer grade probably dried out, maybe treated, or not,

 

[SwedishWings]

yes, layer insl 0.003" Kraft Paper (brown paper they wrap your steaks in) transformer grade probably dried out, maybe treated, or not,

Many thanks, will try this on my next build! I have tried to figure out if old Dagnals used interlayer insulation like this. Do you know?

 

[CJ]

No they did not.

I have a blown C3070 on the rewind station right now.

 

[SwedishWings]

No they did not.

I have a blown C3070 on the rewind station right now.

Thank you so much for all info!

Does C3070 has 5 interleaved layers, like the image (from RDH, chapter 5)? I used this a few times and it sounds good, but never examined an original Dagnal

 

[radardoug]

CJ, somehow we have to save your brain. What an awesome repository of knowledge. And your writing style is classic!

 

[CJ]

Too much varnish has fried my brain. Two cells left and one is flickering.


https://groupdiy.com/threads/marshall-jcm-900-opt-100-watt-dagnall-c3070.57431/

 

[SwedishWings]

Too much varnish has fried my brain. Two cells left and one is flickering.


https://groupdiy.com/threads/marshall-jcm-900-opt-100-watt-dagnall-c3070.57431/

Wow, thanks, that is exactly what i needed! Beers on me if you are in the Manila area some day

 

[CJ]

Maybe, I want to play Efren Reyes!

 

[Walter66]

Great and educational rewind, thanks for showing!
How long do they have used those Dagnall OPT? Is the newer amp series the same OPT (JCM900 combo shown here), it looks different? Do they use chinese parts instead nowadays? I read that about Ampeg, all chinese parts today.

 

[CJ]

early drake, radio spares, partridge,