Another Mystery Transformer Query, sorry...

[tdvt]

One of the things I got in a box of random amp parts from a friend were a few transformers, some roughed into chassis, at least one was still in a box (but not THE box). There is a number stamped on it but Google comes up empty. He may have even bought it from Doug but like 20 years back, he can't recall.


I would to figure out what I have & thought I had things sorted enough to power test it, but what I assumed were the primaries are not measuring (resistance-wise) as I would expect. I tried my best to figure it out without asking here, but I also don't want to connect wall voltage to the wrong set of wires.

Based on the sets/colors of the wires, I was leaning towards it being a 2-voltage primary & 2-voltage secondary with CT heaters & a shield, but all bets are off.

Sets are:

• Red-Red/Yellow-Red   6.9Ω w-CT

• Blue-Blue/White-Blue  121Ω w-CT

• Green-Green/White-Green 0Ω, assume CT

• Brown-Brown/White  6.1Ω

• Black- Yellow- Black/White  5.4Ω;     Yellow to Black  4.4 Ω   Yellow to Black/White  .9Ω

I would have assumed that the black wires were the main primaries but the off-center yellow tap calls that into question. I would have also thought the DCΩ of the red set & the blue set would be closer but first time doing it this way, so nothing to base that on.


Any insights appreciated.

[sluckey]

It's probably a safe bet to assume the greens are 6.3VAC. So, connect 6.3V to the two green wires and measure the voltage on the other wires, including the suspected primaries. It would be safe to set another amp on the bench and use gator clip test leads to patch 6.3V to the PT under test.

[tdvt]

It's probably a safe bet to assume the greens are 6.3VAC. So, connect 6.3V to the two green wires and measure the voltage on the other wires, including the suspected primaries. It would be safe to set another amp on the bench and use gator clip test leads to patch 6.3V to the PT under test.

Very tricky!

Thank you, I would not have thought of that.

I will give it a go.

[tdvt]

Great technique, thank you again. Definitely one to file away.


Interesting readings, not really what I had expected but certainly usable. I am wondering if this was for some sort of specialty application.

Anyway, with 6.08V fed into the green set, I got;

Blue-Blue  560V w/CT

Red-Red    28.9V w/CT

Brown-Brn/Wht   105.8V

Blk-Yellow-Blk/Wht  105.8V   Offset CT,   Blk-Yellow  87V   Yellow-Blk/Wht 17.7V



Can't really imagine what it was made for but the basics are there.  I will have to try to guess on it's current output, but it seems similar in size to e Deluxe Reverb PT, so maybe around 120mA?

[Electron Tornado]

Have you seen this video?

[Electron Tornado]

Here's another helpful video:

[tdvt]

Hadn't seen either of those all the way through, thanks for posting.


Before I go to wall voltage, I am going to test again on 6V fed to the heater winding to verify that the brown set & black set are again reading the same.

Looking at my numbers, it seems curious that I measured exactly the same voltage on both...?

I am now wondering if the brown is primary & the black is a 1:1 isolation secondary but with the added tap. Not sure how you would determine that or why that would be useful.