Allen AC1323 Transistor OPT

this is a cool transformer that Kid Squid sent me,

it is very well engineered, features a nickel core with no air gap but still carries DC, a first in my book,

also, 5 wire gauges are used, another first.

schematic over in the Drawing Board

http://www.groupdiy.com/index.php?topic=52237.0

ok, so where are the pics?

right here>

features a 2 chamber phenolic bobbin out of the Tele v series school,

this is a just ref shot for drilling the lead holes in the bobbin,

here is the info for winding one of these guys,

the core is a sq stack of probably 50/50 Ni, have to do some calcs to make sure, doubt they would use 80 Ni or mu metal for an OPT with a DC bias,

lam size was non standard, at least in the Mag Metals book,

it is very close to 21 EI, but a little bigger, has a 9/16" tongue, 21 EI has a 1/2 inch tongue, 625 EI has a 5/8 inch tongue, so we will rewind with 625 EI to give it a little more horsepower.

the numbers on the diagram match up with the numbers on the lead plate, 1 st pic in post 1.

will post some inductance and freq p;ots tomorrow.

Damn fine work, CJ !
Proper stuff 

hey no problem, fun to take apart something new for a change,

here is the freq graph with and without that tropical fish cap on the secondary,

this is with 1/2 the sec missing due to the broken wire, maybe the bottom end will come up when we rewind,

we have a discontinuity at f(x) = 25,000  >

and here goes the Inductance,

that curve will flatten out quite a bit when in circuit with the DC>

revised  print below  ...

What are A, B, C, and D?  Looks like they just bring the winding out and loop it through a pair of holes before going back around the core again.  What does this do?

i have a new and improved diagram going up in about  10..9...8...7...

ok, try this>

ok we finally did a rewind of this nickel core Allen transistor output for Kid Squid,

did not have any 21 EI lams or bobbins so we bumped up slightly in size to 625 EI,

freq plots were done on the original with a broken sec winding, this transformer uses two sec winds in parallel, when you only use one, the freq plot changes due  to differences in coupling and capacitance,

wire sizes were changed to #36 for both pri and sec as the first wind with #34 and #38 gave DCR measurements that were off from the original readings, so we probably guessed wrong at the original gauges,

here is the new print with the new core and #36 wire>

here are the freq plot and inductance graphs,

frequency response improved quite a bit, do not know how much of that was due to the new core size or the fact that we have both secondaries working, maybe a little of both,

might be able to get away without the stock tropical fish cap that was used originally,
it can be seen on the term plate on the original pics,

induction went down a bit with the super Q, but saturation levels will improve a bit at the very low end, originally induction graph dropped off at 5 hz because we were saturating the core, so we ran the new test at reduced flux levels at 5-20 hz,

here is the coil/core assy, ready for brackets, term plate, hookup and a bake and dip,

there are 10 winds with the split bobbin,

structure goes sec-pri-feedback-pri-sec,

nickel core means low turns which means less phase shift on the feedback winding as the DCR is very low, this improves the stability of the amplifier at the bottom end,

flat freq response improves stability at the top end, phase shift at the hi freqs will be associated with rez peaks, usually the output signal will be close to 180 degrees out of phase with the input signal at the rez peaks,

a dual chamber bobbin allows the designer to experiment with different hookups in order to balance the leakage for the best response, in this case, the push-pull pri goes

left chamber inside wind
left chamber outside wind
right chamber outside wind
right chamber inside wind

and the sec will have the top two parallel winds as

left chamber inside wind-right chamber outside wind

and the bottom two parallel winds as

right chamber outside wind-right chamber inside wind,

so there was some design work done on this OPT,
probably an original design by a guy named Allen? 

> no air gap but still carries DC

The DC is balanced-out. Equal both ways; and trimmable to exactness.