Fender Twin Reverb OPT

[CJ]

022889 is going down hard....

 

[CJ]

putting out some weird mojo,

 

[CJ]

F vs H is required.

 

[CJ]

Max Level is a DJ at KFJC.org

 

[CJ]

Schumacher    1972

wire is pulled Tight.  granite coil.

 

[CJ]

that shim will keep the coil tight as it stretches with heat,  and maybe let a little bit of air past the coil, or not.

and it will keep the core tube from collapsing due to the intense pressure of accumulated turns, 

looks like 29gaM6 Lap 1

 

[CJ]

three secondary winds, so S-P-S-P-S 

 

[CJ]

10 PB (0 .010" or 10 mil press board) between sec winds is darker in color than primary layer insl,

 

[CJ]

take-a-part complete,

big news is the structure,  S-1/2P-1/2P-S-1/2P-1/2P-S

we thought S P S P S  but there were some splits in there,

this explains balanced DCR,

why was the transformer acting up? everything looked cool, no burnt offerings,

but look at the lead breakout,  that brn wire is close to the red wire, there could be some serious AC voltage between those primary leads when the amp is wide open,

we noticed the leads under the wrapper were kind of close, so there could have been some corona going on which would explain the weird wave form, we will find out after the rebuild.

it is possible that someone yarded on the leads when threading them thru the can, who knows.

got a couple of chunks of PB over the leads under the wrapper>

 

[CJ]

pictures help to fill in missing info from notes,

 

[CJ]

secondary leads,

 

[CJ]

outer secondary, pretty stiff wire, probably #17 AWG

 

[CJ]

unwinding a primary section, spooling it up so we can measure the length to get the MLT (mean length turn) of the wind which allows computation of DC resistance per 1000 ft so we can see how the wire stacks up to the wire chart, older wire usually has less DCR per 1000 ft because the copper is better or the insulation is thinner, or both.

if you just let the wire fall on the floor, it makes measurement a hassle, (bird's nest)

 

[CJ]

inner primary,  all the primaries are 435 turns, so we have  1740:80 ratio = 21.75:1 = 473:1 Z ratio,

473 x 4 ohms = 1892:4 ohms in a perfect world.  DCR will change that ratio a bit as not all the voltage will reach the secondry, so the voltage ratio might be 23:1 = 529:1 Z ratio = 2.1K:4 ohms, but Z changes with frequency, speakers are non linear, the transformer is non linear,  so no big deal.

 

[CJ]

and that is a wrap,  nice coil, no turns missing, no warped core tube, layers were neat and right over the top of each other for low leakage, we will get a real blueprint up now for this Blackface/Silverface Twin Reverb classic transformer which has had a lot of music played through it,

 

[AnalogPackrat]

Excellent job, as always, CJ.  Glad to see you're still running your winder in forward and reverse.

Cheers,
AP

 

[CJ]

that winder is going 24-7, i am about to snap! 

here is the print right here>

 

[Bo Deadly]

How many of these have you done?

You should organize all of the files, pictures and spec-sheet images into directories by transformer and make one big zip file. I can think of multiple scenarios where that might turn out to be a good idea.

 

[CJ]

www.vacuumbrain.uk   

 

[clintrubber]

Nice thread, great info! 

FWIW, some of the Japanese silverface clones from Guyatone took the liberty to add an additional 8 Ohm output-tap.
Curious if that was because the clone-amp didn't have the capability to run at mismatched loads (like the original),
or that Guyatone simply liked to provide an additional feature.
(They didn't use it on all their models though. The snippet shown is of the GA-1100D.)