Help Me ID this Modulation Transformer

[KI4YAN]

I found an old modulator the other day, sans all the tubes, but with good iron. All the end-bells were rusted up, but cleaned up nice with some wire brushes and new paint. Since the rats had eaten all the cloth insulation, both the meters were cooked, and the chassis was warped badly, I salvaged what I could. All the transformers got new leads and repainted end-bells.

Now, I have a 12W PP driver transformer, (was labeled, so I have that info) a 400VA power transformer, haven't decoded the primary winding yet, and a 325VA modulation transformer. I say 325VA, because the core is sized to handle 325VA at 60Hz. This transformer has six primary leads, two reddish, two blue, and two brownish. A pair of (looks like it had 807's) 5 pin sockets with plate caps was connected up as so: blue leads to the plate caps, brown leads taped up and not used, red leads tied together and connected to one side of a mA meter, reading 200mA full scale. The secondary has 12 tie points on a bakelite board, rivited to the metal end-bell. Points 5 and 6 were tied together, points 7 and 8 were run out to a pair of ceramic insulators on the back of the chassis. The 12W PP driver transformer is marked 4000-6000R P-P to P-P Grids and had a 6L6 driving one half of the primary winding, and the secondary winding pushed the grids (if it was 807's) of the modulator tubes in push pull, probably class AB2.

The modulation transformer is marked on the primary side end-bell as follows:

                  SNC           5 P 3 2 5
            Made in USA

Does anyone have any information on this transformer, or how to determine the ratios needed? It's not Zorched, as I put it on the megger at work. No primary-secondary shorts, and no charred spots or burnt smell. If it was a simple one-to-one transformer, measuring impedance ratio is not a problem, but with the multi-tap board on the back, I'm stumped.

[W7XXX]

Turns ratio is equal to voltage ratio. Apply 10 vac to the primary and then measure the secondary taps. I use 10 volts because it makes this simple ... example 10 vac on primary and secondary measures 12 vac = ratio 1:1.2 ... or secondary measures 20 volts 1:2 hopes this helps.

[KI4YAN]

That would be great, but i don't know how many of these are taps, and how many are separate windings. There are 12 solder tags on the back of this thing...

[Steve - WB3HUZ]

Make a 12 by 12 spreadsheet. Then take an Ohm-meter and check each tap against every other tap and note the resistance or if it's open. Once you do that you should be able to determine the two sides (primary and secondary) of the transformer and the various taps off each.

That would be great, but i don't know how many of these are taps, and how many are separate windings. There are 12 solder tags on the back of this thing...

[KI4YAN]

OK. the core area suggests a 60Hz VA rating of 325W. Primary is presumably push-pull, with what appears to be 30% UL taps. The center tap for the primary is brought out as two separate leads. Secondary appears to be dual wound, with identical but opposing tapping arrangements, I.E., connect taps 5 and 6 and call it a center tap. the overall winding ratio is 2:1+1, or if taps 5 and 6 are connected, 1:1.

Unfortunately, this seems to complicate things, as most modulation transformers i hear about have ratios of 1:1.25, 1:2, 1:5, ect.

Does anyone recognize this description? I'm working on getting a picture of it so we can have some visual ideas as well.