UA 176 Output XFMR - need pri inductance

[CJ]

simple, green primary, red secondary, 

just start at the far left notch and move up a notch for every tap,  and tape some numbers at the ends JIC.

 

[Winston OBoogie]

i think i see how this went down, Putnam built the 610 preamp with the 12 BH7a running single ended which requires a gapped transformer,  then he built the 176 compressor with the push-pull 12BH7a which does not require a gapped transformer, so he gabs the gapped transformer anyway and it has enough  inductance to work so he uses it, that is what engineers do, they grab stuff off the shelf that works then they use it.  because it saves time and money. and engineers are all about saving money.

It's probably something along those lines in terms of using an existing part, although the transformer was used in the 175 and the 1008 preamp before the 610.  Both single-ended applications (1008 & 610) used a 12AY7 output, not a 12BH7.

I really wish I'd posted all the winding data when I had it,  along with everything else I had that was lost.
I'm still sticking to the recollection I have of the 5946 not being gapped though...  I had a decently long chat with dear departed Tom Reichenbach about it while he looked over the docs.  Of course, I have had laser brain surgery since then...  but I'm relatively certain I didn't just invent a memory.  I've lost memory and am even stupider nowadays, but that's another kettle o' fish...  I hope! 

Anyway, I just remembered that I sent a spare actual original 5946 transformer to our own David Bock for something he was doing. 
Maybe he still has it hidden in a shop drawer? 

 

[bockaudio]

If you had asked for ammeter readings of microphone transformers I would already have that.
What frequency and level were you interested in the 6003 for?
BTW the 100Hz reading I gave you was from an expensive LCR, which has proven true as a quick way to get these numbers.

 

[bockaudio]

Because inductance varies with frequency and level, there are so many answers to this basic question that it would congest the spec sheet, so manufacturers address those who paint by numbers by describing typical implementations, which is adequate 90% ot the time. It's only when we ask a little more than the basic role of converting voltages that these info are needed. Indeed reverse engineering is one of these circumstances.

Listing the 100Hz number would be an indication that, "at least we're trying".
From what I've seen over the years, even the impedance substitution method they use  is a wishful best case.

 

[CJ]

use 20 volts AC into the primary.

take current readings at 20,30,40,60,80,100,500, and 1000 Hz

it don't take long once you get set up

Thanks!!!

 

[CJ]

we did some pri ind tests on a finished coil of 4500 turns on a sq stk of 75 EI 
in a moment, the results of that trial,...

20 Hz  20 VAC :


Lap 1    1113  Henries
Lap  3  574 H
Lap 5  410 H
Lap 7 328 H
Lap 9 241 H

Butt stack - no gap: 96 H
Butt Stk 3 mil gap 51 H
7 mil  37 H
10 mil 30 H

that is all.

 

[CJ]

ok we used a Lap 4 on the core got 550 Henries at 20 Hz, 20 VAC,

these guys are flat from 5 Hz to 100 K Hz,

labor intensive because of the taps, so not something for mass production,

if you want to wind, use 642 turns of #36  split on a chambered bobbin (321 + 321)
then a reverse wound primary with taps for the top half of the tube, split 2250 so 1125 + 1125 #38
then another 642 turn secondary,
then a fwd wind primary just like pri #1, , CT is both finishes,
then another sec
parallel secondaries and put it on a 75 EI core Lap 4 and you are done.

reverse wind pri keeps AC volts even on taps,

3 mil Nomex between p-s

DCR is 30 ohms sec, 1 K pri

wind coil tight! (wire just fits, which is what you want for low leakage-no air between coil and lams)

Heyboer will sell you bobbins, U Frames and End Bells , Edcor for the lams,
cut up old LP cardboard cover for bobbin divider,
we used red and grn solid colors for sec, one blk wire for pri start #1,
you can get 8 different colored striped wires here>

https://www.ebay.com/itm/22-AWG-Gauge-Stranded-Hook-Up-Wire-Kit-5-ft-Ea-8-Color-w-stripe-UL1007-300-Volt/293340684182?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

[emrr]

I measured 63Hy@100H in my 6003.

One I have here (UTC-PD) measures 46Hy  in circuit in a 1016 preamp, no tube installed, with an Extech handheld meter at 120Hz.  1H3 on the sec.  Can't speak to test signal level. 

1016 can be  run with a 12AY7 or 12BH7 in the output stage, for a change in max level (+22 versus +30 dBm), preamp or program amp use.