[Guest]

I'm in the process of restoring a Model 70 that was handled VERY roughly and the Power transformer was separated from the chassis. I purchased this unit in pieces and I have reconstructed it down to the power transformer. I cannot determine the wiring configuration for the transformer It has a fiber bottom plate with 12 solder terminals on it. I have looked through all of the schematic information I could find on the 70 but I could not find a hookup diagram for the transformer. Could you help me with this?
Thanks

[Ron Ramirez]

Hi

I've never seen a 70 that had a terminal board on the bottom of the power transformer; all of the Model 70 power transformers I have seen have wires protruding from the bottom.

Sounds like your set's power transformer was replaced at some time, possibly with an older Philco power transformer? Look and see if there are any numbers on your transformer. If so, please post them here. Perhaps with that info, we may be able to solve your mystery...

[Guest]

The case looks like a Philco product. The only marking I could find is number 4234T stamped on the case.

[Ron Ramirez]

Bingo, that's what I needed to know.

Part No. 4234 is the power transformer used in Model 20. Model 70 used Part No. 5117.

Part 4234 is incorrect for Model 70 as it has an extra 5 volt winding designed to run two Type 71A tubes, in addition to a 2.5V winding, a 5V winding for the 80 rectifier filament, and a high voltage winding.

Model 70 requires a high voltage winding, two 2.5V filament windings (one for the Type 47 output tube and the other for the rest of the tube filaments except the rectifier), and one 5V winding for the 80 rectifier filament.

Are you sure your set is a Model 70? Could it be a Model 20 chassis in a 21 cabinet?

Photos would be a big help here, if you can share any.

[Guest]

Attached are two photos of the chassis, I'm pretty sure it's a 70, I had one about twenty years ago but a lot can change with ones memory. When you mentioned it was a model 20 transformer I looked at the 20 I have and that confirmed it. Now I'm wondering how the previous owner was able to operate it on this transformer or if it was never hooked up to begin with.
(I don't see how a radio could be handled to such an extent as it would tear a power transformer off of the chassis and not cause any more damage than it did.) Thanks for the information.

Note from site admin: Sorry, but the photos which were attached to this post are no longer available.

[Ron Ramirez]

Yup, that's a 70 chassis.

Don't know how it could have operated properly with a transformer from a Model 20, unless someone used one half of the center-tapped 5 volt 71A filament winding on the 47, or if they used the center tap for one side, and both ends of the other side...

At any rate, you will need a power transformer, one designed for your 70.

Oh, when I acquired my 650B, its power transformer was torn from the base...only because some dimwit removed the mounting bolts.