Triad AO-3039T Output Transformer

Help Support GroupDIY:

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
fresh meat on the table, this time a classic Triad as used in the Gates amplifier,

thanks to Andy for sending it, and a double thanks for doing the dirty work of taking it out of the can.
i did not want to deal with that goop. Triad was involved in heroin smuggling in order to avoid bankruptcy.
They would send the transformer cans to Pakistan, have them packed with black tar heroin and shipped back to the US.
i'm a two time loser and a third strike for drug dealing would have meant the slammer with bubba.
not that it would be a bad thing, my last visit with bubba was the most monogamous relationship i have ever had, but that is a whole different story.

here is the corpse right here>

g1.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
this guy can handle unbalanced DC so we expect to see a butt stack, and that is what we have.

75 EI lam which features a 0.75" tongue, we have a 1.125" stack so that means we have a1.5:1 aspect ratio which some folks say is optimum for transformer design, reasons unknown.

g2.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
easy delam with the butt stack, a little heat and off comes the top.

press board core pads, (blue paper)

g3.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
getting smart in my old age, using cavity search gloves so i do not have to scrub off black tar heroin.

g4.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
once i pulled those two core pads, the coil popped right off as things were still warm.

wax was used to impregnate the coil, black tar was the potting compound.

wax is easier to deal with than potting compound. it has a lower melting point.

not as low as regular parafin wax, as it is poly-crystal wax, especially blended for transformers.

some folks say that old school wax adds mojo which is missing today.

this would show up at the high end, as the wax determines the capacitance of the coil.

capacitance dictates the shape of the freq curve as related to peaks and valleys.

but most of this action occurs at about 50 K Hz to 1 M Hz.

g5.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
luckily we already have a mandrel for 75 EI, now we can use the counter on the winding machine,
if this is anything like the Triad HS-50 OPT, then there will be many turns of fine wire involved. 10 KP wrapper removed...

mandrel.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
first section to unwind appears to be the 600 ohm secondary wind.

tape the lead wires down so they don't break, we want to keep track of starts and finishes.

first lead on outside is not a start, it is a finish. we have two wires connected to each lead which means two secondary sections in parallel. so coil structure is probably sec-pri-sec.

Triad is not know for complex coil structures, we leave that to Peerless.

g6.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
it is a lot more fun than taking apart a transistor, i am glad you like this stuff,

secondary layer insulation looks to be 0.002" Glassine paper,
this type of insulation was used by just about everybody used back then, it can be hard to measure the exact thickness as it absorbs wax pretty well. and it is pretty old, like 50 or 60 years old,

g7.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
8 layers of wire taken off, 800 turns, easy math per layer,

this will be the pri-sec insulation which is usually thicker than layer to layer insulation as you do not want the hi voltage primary punching through to the sometimes grounded secondary.
and also, you do not want the heavier secondary wire to damage or deform the small primary wire.so voltage protection and mechanical protection. and in some instances, the thickness of this layer can be used to set the pri to sec capacitance.

g8.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
now the real work begins, counting the fine wire primary turns. looks like part of this layer almost got knocked off the former by the outer secondary,

g9.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
pri-sec insulation looks like 1 layer of 2 mil Glassine, 1 layer of 5mil Glassine or Kraft Paper, can not tell which, and 1 layer of 2mi Glassine.


this comes out to about 0.010" total with the wax.

g10.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
looks like the initial failure happened, as it usually does, on the connection between the lead and the magnet wire, in this case, the blue wire.

but this 0.003" primary wire (probably 40 AWG) was very fragile anyway, as i was unwind the coil, it would break off even with no tension, this happened about every 100 turns, so even if Andy managed to repair the blue splice, the transformer would have been very undependable and quite possibly might not have worked or not at all. we are dealing with fine wire that was probably getting hot due to being operated around the clock at the FM station. It was pretty rotten, with not much enamel insulation left.g11.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
a couple hours later and there is the red start, usually marked by a black dot on a transformer diagram. then the start of the secondary will also get a black dot, the two dots will show the phase relationship between the pri and sec leads in case this is important, like in NFB to a phase inverter of a guitar amp.

23 layers, 3600 turns total primary, which comes out to about 156 turns per layer average.

layer to layer insulation was 1 mil Glassine paper (0.001") which makes for a nice smooth surface for winding the fine wire in tight layers. Triad is the king of winding the small wire, as witnessed by the famous HS-29 Pultec innerstage xfmr. UTC is a close second with their dual pie foldback wound input transformers such as the A-10 and HA-100-X as used in the LA2a compressor.

there is very little space between these 0.003" turns, you have to keep the tension just under the breaking point of the wire to keep the turns from crossing over each other which can resulting a failure. i do not think i have ever seen one crossover on the UTC/Triad?Peerless stuff that i have i unwound which is amazing. you need a really good machine to lay that stuff down. Doing many coils at a time helps as the ends of the insulation do not cave in, as the insulation is put down in big sheets which covers all the coils being wound.

g12.JPG
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
what remains under this pri-sec insl. is the other 800 turns of the parallel 600 ohm secondary.

so 3600 turns pri / 800 turns sec = 4/5:1 turns ratio which squared, is 20.25:1 impedance ratio,

so 20.25 * 600 ohm sec = 12,150 ohm primary.

now you have resistance in the primary wire, which can eat up a few milli-volts, so after losses you might end up with a perfect 20:1 Z ratio which equals exactly a 12K to 600 ohm transformer.

engineers always start with an impedance ratio first, the turns ratio comes after that.

this transformer matches it's spec in the catalog, many times the turns of a transformer will be off by quite a bit so that the actual impedance ratio is quite different from the advertised value.

g14.JPG
 

andYz00m

Well-known member
Joined
Apr 15, 2020
Messages
54
Location
Santa Cruz, CA, USA
Dude. Fascinating. I think your hair looks lovely!

What are the mathematics behind the turns to impedance ratios? Why do you sqaure them?

Sounds like if this thing hadn't been beaten and smoked to death it may have been a shining example of its kind.
 

CJ

Well-known member
Joined
Jun 3, 2004
Messages
14,313
Location
California
yes, turns ratio squared = impedance ratio.

here is a cut sheet for the lamination used>

75EI.JPG
 
Top