Fender Super Reverb Power Transformer

[CJ]

this thing right here is out of the same amp as the OPT ,

never hacked one of these before,

toughest transformer i have ever had to take apart, i thought it was sealed up pretty good and escaped the salt water but the variac blew a 3 amp fuse so we are out of luck,

trying to get the lams apart with the heat gun did not work,

 

[CJ]

this thing was impregnated with gray epoxy, everything was locked together, lams were impossible to get apart, so we had to take the xfmr out back , at night, and hack the top off the lams with a cutoff saw which had the neighbors wondering what all the sparks were about,

you can see the heat affected zone from the cutoff saw, which we used from both directions,
then we used a hacksaw to finish the job, thus the difference in color in the middle,

the coil was still bonded tight to the lams, that epoxy got in between the coil former and the lams,
so we had to put the coil on wooden blocks and used a sledge hammer to knock out the lams, swinging it pretty good, no wonder these transformers never break down or buzz,l wrapper with it on the way out,

that outer winding was pretty close to the core, the epoxy took the coi

 

[CJ]

leads all come out of one hole, nice Premier Twin 12 we get to work on also,

 

[CJ]

had to sand the coil down til we hit cardboard, then spray the whole mess with some pb blaster,
then use a piece of scrap steel to punch those lams out, even then, the outside lams were still stuck to the coil, but we got er done, Heyboer is sending me some 138 EI and a bobbin,

 

[CJ]

you can see the indentations of the lams in the epoxy, no wonder those pecker heads wouldn't come out, if anybody asks you to rewind a fender pwr trans like this one, take a pass, tell them to get a pos hammond for $109

 

[Matador]

tell them to get a pos hammond for $109

Not to derail too much, but are the Hammond transformers of a quality commensurate with their price? I've bought a few power transformers as one-offs from Alibaba, and visually they appeared identical to the Hammonds, and tested fine, for like 1/4 the price.

Can't wait to see if there's anything magical with these Fender transformers!

 

[CJ]

I bet they use the same factory, it is hit and miss with the budget transformers,

 

[GussyLoveridge]

tell them to get a pos hammond for $109

I had no idea that Hammond didn't make a quality transformer.

 

[CJ]

they are alright if you like 6.8 volts on your heaters,

 

[CJ]

tearing into this coil, it is wound old school, with the secondary finish being the CT splice, this helps shield the high voltage emf, since the ct is grounded, the outer layer acts as a shield,

they also put the two business ends of the secondary right on top of each other, this requires care as you have about 340 volts times 2 next to each other, which means 680 rms which transcribes to about 1000 volts peak! but it is only 60 cycles, if this was the output transformer and you had 1000 v at 10 KC, you might have some creepage. ,

having the two HV layers on top of each other might help to cancel emf like twisting heater wires but i am not certain of this.

now i know why the flood the tanks with epoxy, this is called end capping in the xfmr processing dept, we used to pour special sand into the gaps to keep all the epoxy from running down into the windings, had a big sand box raised up on a table, you would have to wait overnight while one side dried, then flip it over and do the other side. this keeps the xfmr fro arcing out to the core and adjacent winds,

you can see a tiny bit of this epoxy leaked down into the winds, those winds move just a tiny bit with the ac, if you tie one end down and the other end is moving, you have a snappy gator. guitar pickups do not have the voltage to make the windings move much so you can get away with hard epoxy like Tony Iommi,

 

[CJ]

down to the primary, plenty of epoxy , won't hurt the big wire,

 

[CJ]

that potting compound strips the insulation right off the wire during the unwind,

 

[CJ]

and there's your former and the 1/8" wood shim,

 

[CJ]

ok then...

 

[john12ax7]

Not to derail too much, but are the Hammond transformers of a quality commensurate with their price? I've bought a few power transformers as one-offs from Alibaba, and visually they appeared identical to the Hammonds, and tested fine, for like 1/4 the price.

Isn't Hammond made in Canada? Or are they doing stuff in China now?

I've only used the Hammond hifi series. But it seems they also have a guitar amp replacement lineup.

 

[CJ]

If they can sell a big power transformer for 109 then it be offshore.

 

[soapfoot]

Hammond’s manufacturing sites are in Canada, US, Mexico and India.

 

[CJ]

If you do a cost analysis you can see why they can not build stuff for that cheap in the US

Copper 20 bucks a pound, steel 10 bucks a pound , winders wage 24 an hour, tape, insulation, end bells, paint, varnish, wire leads. Shipping, profit margin, worker benefits. Rent and electricity. Shipping costs, r and d engineers. QC testers , advertising

 

[soapfoot]

For whatever it’s worth, I’ve been using Hammond PTs recently and have been very happy with them. Maybe I’m easy to please?

As for heater secondary voltages, most of my vintage power transformers also output higher-than-bogey numbers, probably just due to increasing line voltage relative to when they were made. Usually it’s within 5% still and I don’t sweat it too much.

 

[dmp]

I'm curious about the load / no-load heater voltages. If it is just turns ratio it would be hard to mess up
My line voltage is high, 121v so heaters are also high. On a build can drop the h+ with resistors