Fender Amplifier Transformers

[OlegRadio]

some of these are measurements only. some are winding prints.

Thank you very much for the great work done!
Can this data be transferred to third parties or published?

P.S. I can't put Like! :-(

 

[CJ]

Open season.

 

[Tubetec]

I had a blues junior for repair today , it was redplating after a while on one tube and sounded more like single ended 5W,
The usual complaint , a powertube socket had developed dry joints , meant it was out of the HT circuit , so the other tube soldiered on , luckily they were tough Russian EL84M tubes ,


I know you said you no longer handle these Fender amps ,

This one works fine after re-wetting and plumping up of the solder Joints around the powertube sockets with quality 60/40 .
I have had to bridge lifted tracks from the tube sockets with copper a few times on these amps , but I never failed to get one going again .

While I was in there I took a quick measure to make sure my primary windings were intact
they measured 105 and 106 ohms on the toolbox grade Fluke 177 .
The blues junior seems to be missing from the collection above ,

 

[CJ]

i work on the blues jr, just not on the deville, hot rod stuff,
the bigger spk cab has a horrible resonance problem, like the tacoma narrows bridge that self destructed,


i like the blues jr, put a good speaker in there and some Amperex,

i gotta work on a hot rod deluxe limited edition because it is a house amp, ugh,

we have a blues jr, i will check the OPT,

 

[danfrank]

Thanks for the info! What I find most interesting is how some OTs have decent interleaving and others are primary wound then secondary wound on top.
Thanks again!

 

[CJ]

Output transformers in power amps have enough juice to charge up all the parasitic capacitance without losing to much high end.

 

[Tubetec]

The good balance on the Blues Junior primary seems to point towards a carefully interleaved arrangement ,
often in other transformers Ive measured you find a difference of 10% or more in the primary dc ohms.

 

[CJ]

Marshall has balanced dcr as well.

The Peerless 16431 is probably the most over engineered transformer I have ever seen.

Six different kinds of insulation, reverse winds on the primary, quad fillar wound secondary, 5 section primary, 5 nickel lams added to the center of the core, instructions to wind super tight, used in the Dynaco Williamson amp, considered the best 100 watt OPT out there unless you consider McIntosh stuff.

 

[CJ]

OK I did in fact take apart the blues junior, I think,

https://groupdiy.com/threads/fender-blues-junior-opt.68868/#post-876988

 

[lukas]

...some blue print for Peerless 16431?

 

[CJ]

Yes. In here somewhere>
https://groupdiy.com/threads/marshall-jcm-900-opt-100-watt-dagnall-c3070.57431/

 

[Rusan]

The Peerless 16431 is probably the most over engineered transformer I have ever seen.

Six different kinds of insulation, reverse winds on the primary, quad fillar wound secondary, 5 section primary, 5 nickel lams added to the center of the core, instructions to wind super tight, used in the Dynaco Williamson amp....

Peerless didn't have much choice. Enclosing four tube stages (two of them RC-coupled) and a transformer inside a global NFB loop with 20 to 30dB of NFB isn't a good idea anyway, so it required a near-perfect OPT for any chance of pulling it off without oscillation. Besides the usual phase compensation cap across the feedback loop resistor, my buddy's Heathkit W4-AMs also had two series RC networks to tweak frequency response and phase shift; one across the first stage's plate resistor, and one from the 16 ohm tap (the NFB node) to ground.

IIRC, the original D.T.N. Williamson spec required to theoretically assure stability was something like flat from 3Hz to 160kHz, and I think the Peerless 16431 impressively achieved something like 10Hz to >100 kHz, with very low phase shift. Heathkit and Eico's Williamson amps (both of which used Peerless iron) were still notorious to oscillate once the caps started aging, or if presented with a speaker load they didn't like. Can't imagine why anyone would design an amp with such low phase margin.

 

[CJ]

some of those Williamson's would blow tweeters on a regular basis becuase the OPT was not up to snuff,