Power Transformer for Echoplex EP-3

[CJ]

wonderful invention that Echoplex, wonder if Jimi had one, Hendrix that is,  Jimmie had one, didn't he?

you shook me off the first LP has a nice echo solo,

now there are about 5 bolts holding the echoplex chassis to the box, one is shorter than the rest,

why?

this is why>

 

[CJ]

so we have a unit doing a thirty minute bakedown in the EZ Bake oven at 225, then de-lam,

why not document the thing, don't do too many low volts pwr transformers,

beats shooting down jets in turkey of fishing without a license,

stay tuned for the exciting details...

nice link - http://www.regiscoyne.com/echoplex/

tweeker thread>  http://forum.metroamp.com/viewtopic.php?f=12&t=41358

wiki blurb>
    Duane Allman (intro-Black Hearted Woman)
    Chet Atkins
    Tommy Bolin especially for the "ray-gun" effect heard on Billy Cobham's Spectrum
    Wes Borland
    Miles Davis
    East Bay Ray
    Don Ellis
    Jerry Goldsmith
    Eric Johnson
    Esteban Jordan
    John Martyn
    Brian May
    Steve Miller
    Gary Moore
    Jimmy Page
    Chuck Rainey
    Randy Rhoads
    Joe Satriani
    Neal Schon
    Sonny Sharrock
    Andy Summers
    Eddie Van Halen
    Joe Walsh
    Keller Williams
    Neil Young

 

[CJ]

looks like 75 EI, Lap 3,

42 lams,  40 + 2 keepers,  1- 1/16 stack = 1.0625,

lam thickness = 1.0625/42=0.025"  only comes in non grain orient,

 

[CJ]

we have a layerd paper job, (those poor old winders) that is about to be converted to nylon,

 

[CJ]

CT not used so they snip it,

leads pre-stapled to 61 PB  (press board 1/16 thick)

Poly + PB wrapper, 2 layers,

 

[CJ]

entrance wound, looks like 7.62 x 39 hollow point, 

 

[CJ]

primary wound nice, 10 layers of #32 for 729T total,

sec was 180T of 24AWG,  drops 120 down to 30 V-ac,

 

[CJ]

parts is parts, if you eat at J Box,  ???

there is your former and pri wire, spread the yams apart while they are still  hot, 

i mean lams,  ;D

otherwise they get stuck together, poly wax, not varnish,

think we will add some end bells so the next yahoo (me) who decides to mix up the screws  :-X  will not punch a hole in the darn thing,  maybe we did it subconsciously as to warrant a write up,   
carl jung would know,  but he ain't yung anymore, 

 

[CJ]

this is how we roll right here>

 

[CJ]

we mounted this rewind job back into the echoplex,

dropped the AC sec voltage down from about 28 to 23, so now the rectified DC is more in tune with the print,

this seems to have improved the sound, you can now turn the echo sustain knob up all the way with no oscillations or feedback, this means you get way more than 3 or 4 repeats,

now that tape relay had a problem, it would only pull in half the time with the lower voltage, so we changed the power resistor feeding it from 22 ohms to .47 ohms, and now it pulls in every time,


we moved the mounting holes back so now you can not drill a hole in the xfmr especially with the long screws if used by accident,

so if you want your EP-3 to sound like the old vintage units, try the mods and drop the voltage, this circuit seems to be sensitive to supply voltage,  runs more quiet also, added a 1000uf/50 across C1 also,

 

[CJ]

here is a new print for the EP-3 pwr transformer that we wound,

dropped the wire gauge on the sec, no need for #24,

lower sec voltage will improve sound,
measured the Henries in real time, 5,5
perm is 2,137 but would increase at 20 Hz, we used 60Hz,

 

[API]

Great stuff CJ!

I am working on a EP-3 myself at the moment and will try the mods you mention.
How did you drop the AC output?
Did you do this in the rewind??

Also, these transformers are US voltage only in original form, correct?

 

[CJ]

yes i just dropped the turns ratio, you could lower voltage with resistors also,

no provisions for 220 VAC noticed on the orig xfmr,

there are youtubes for winding your own cart also,

 

[API]

Thanks for the info.
Will try to drop the voltage and see what happens.

Just reccieved a small restore kit so will get this up and running this weekend.
Mine is an apparently rare and early red plastic version, supposedly only 400 made in 1971.

 

[goldstache]

Hey CJ, got a repair in, same mount piercing lams.
Got a current rating on this bad Larry? I’m looking to source a replacement.

It’s a later EP3 (1977) and I think 120v - 30v might be a good target.

Looking forward to any info you might have.