Triad 3758 Transformer ID help
« on: June 01, 2018, 05:11:10 PM »
Hi all,
Looking for specs on these. Unfortunately the few old Triad catalog pdfs I have found don't have anything on these. They say triad and have 3758 printed on them, but no specs.

Anyone have any clue?


CJ

Re: Triad 3758 Transformer ID help
« Reply #1 on: June 02, 2018, 04:08:52 AM »
probably mic or  line input if it has gold pins,

80 bucks on evilbay?

no info on those private label numbers, sorry,   :-[
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

shabtek

Re: Triad 3758 Transformer ID help
« Reply #2 on: June 02, 2018, 10:39:54 PM »
This can only mean 1 thing...
"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ

Re: Triad 3758 Transformer ID help
« Reply #3 on: June 03, 2018, 08:21:13 PM »
probably mic or  line input if it has gold pins,

80 bucks on evilbay?

That's what I'm hoping for...as for price, about half that. One might be able to go lower. Seller has a lot of them and accepted my best offer (actually countered with a price $0.01 less per pair...first time I've ever gotten a better counter than my own best offer)

Re: Triad 3758 Transformer ID help
« Reply #4 on: June 03, 2018, 08:32:31 PM »
This can only mean 1 thing...

Exactly...wait. What?

Re: Triad 3758 Transformer ID help
« Reply #5 on: June 05, 2018, 11:40:02 AM »
These arrived yesterday. I poked at 2 of them a bit with my multimeter and here's the early results

Pins 8-2: 3.62k/3.65k Center tapped at Pin 1
Pins 8-1: 1.97k/1.98k
Pins 1-2: 1.64k/1.65k

Pins 3-4: 5.21k/5.25k

Values are just direct DC resistances. Nothing seems tied to the can.

Hoping to get my act together at some point to work through Pucho's Transformer measuring guide. but if this is enough to ring any bells, let me know.



shabtek

Re: Triad 3758 Transformer ID help
« Reply #6 on: June 05, 2018, 02:14:24 PM »
Donate to science...
"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ

PRR

Re: Triad 3758 Transformer ID help
« Reply #7 on: June 05, 2018, 06:34:16 PM »
With those huge DCRs, I smell geo-transformer.

Through the 1950s there was much work with with seismographs and particularly oil exploration by recording echos through the rocks. These need very extended "bass" response, to below 1Hz; treble was sacrificed.

Re: Triad 3758 Transformer ID help
« Reply #8 on: June 06, 2018, 01:53:21 AM »
Triad geoformer type G85

DCR

1 to 4:  3129 ohms
8 to 6:  3243 ohms

Re: Triad 3758 Transformer ID help
« Reply #9 on: June 06, 2018, 06:44:14 PM »
Sigh...
I guess this gamble didn't pay off. Is there still a market for geoformers or am I stuck with these?
« Last Edit: June 06, 2018, 08:09:02 PM by thecr4ne »


mjrippe

Re: Triad 3758 Transformer ID help
« Reply #10 on: June 07, 2018, 12:39:42 PM »
Sigh...
I guess this gamble didn't pay off. Is there still a market for geoformers or am I stuck with these?

Passive DI for Bass?  ;)

CJ

Re: Triad 3758 Transformer ID help
« Reply #11 on: June 10, 2018, 03:14:56 AM »
could be single plate to push-pull grid innerstage,

check voltage ratio, should be around 1:2  if innerstage,

never seen an octal geoformer,  or a geoformer with a CT, usually balanced dual coils for series or parallel,

do not think they would use gold pins either,  and if the geoformer is being towed underwater, they would want a solid connection, not an octal socket, so do not lose hope just yet, check freq response if you have the means,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Re: Triad 3758 Transformer ID help
« Reply #12 on: June 10, 2018, 12:41:18 PM »
Any considerations to be taken into account for the high resistance or would I go about it like a line level transformer?

For voltage ratio, run 1kHz through it at 1V or so and measure output voltage right?

And for the freq response, white noise in and out to a spectrum analyzer?

Forgive me, I'm somewhat new to the wonderful world of inductors. 

CJ

Re: Triad 3758 Transformer ID help
« Reply #13 on: June 11, 2018, 03:07:09 PM »
1 K at 1 volt is perfect for the ratio test,

just inject 20K Hz and see if 20 K Hz comes out for the freq test,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Re: Triad 3758 Transformer ID help New
« Reply #14 on: June 11, 2018, 07:29:45 PM »
Ok, I did what I could on one of these with fewer alligator clips than I would've liked. I'll dig for some more leads and try again tomorrow.

So, if I've done things correctly, Voltage ratio is 1:1, or considering the center tap 2:1+1. To clarify, 1kHz at 1V in to pins 3-4 measures 1V on pins 8-2, and 0.5V on pins 8-1, 1-2

I ran a few tests with Rightmark audio analyzer and ended up with some encouraging results. Below is a frequency response graph comparing the wiring it "backwards" and "forwards" the white line is pins 3-4 as the primary, 8-2 as secondary, the green plot is 8-2 primary and 3-4 secondary. Let it also be noted that the input gain knob on the USB interface was at about +4dB using pins 3-4 as the primary, and at about +40dB using pins 8-2 as the primary.

Based on the plot, I think it's safe to say this is an audio transformer, primary across pins 3 and 4, secondary across pins 8 and 2, center tapped at pin 1. Can we infer a rough idea of the impedance ratio from the input gain difference? I don't have many pots/variable resistors handy to actually measure it. I'll try to play with this more tomorrow if there's time.

Would love any feedback re: my results and/or any flawed logic or methodology.

Here's the plot:







 
« Last Edit: June 11, 2018, 08:06:57 PM by thecr4ne »


 

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