transformer cross reference #s?

[mikhett]

I have some old ampeg PTS and OTs but i cant tell what the voltages are onthe pts the only  #s are # 151.On a full wave SS bridge they put out about 380 volts.I know they were made by a company in Chicago called "Electrical Windings it would be nice if i could CR them with Hammond.

[sluckey]

I doubt you will find a cross reference book. I would look through all the Ampeg schematics in Doug's library. You just might find that #151. If so, you can get a feel for the PT ratings based on the circuit it's used in.

It is pretty easy to tell what the voltages are just by using a meter. Use the ohm meter function to group wires together. Then apply primary voltage to the primary and just measure voltage for all the groups. You've already identified the primary and HT secondary. Probably all that's left is a filament winding? Current ratings will be tough to determine without knowing more about the PT.

For the OTs I would use the ohm meter function to group wires together then determine the turns ratio which will allow calculating the impedance ratio. Then guess what the power rating is based on physical size.

All this would be much easier if you can find a schematic that the transformers were used in.

[AZJimC]

The 151 OT, I would bet is 6600 ohm primary side. Here is a listing for it.

http://www.fliptops.net/catalog/p-100605/output-transformer-ot151a-for-many-ampegs