Actually, the CTC-7A Had two 5U4's mounted on top of the box the transformer was in. The other series of that chassis run had them on the chassis in front of the transformer.
I believe it was the CTC 10 that went to silicons.
CTC 4 had seleniums, and CTC 5 had 5U4's on the chassis.
I have also seen a 5U4 on the transrormer of one Bendix tv, and a 5Y4, I believe it was, on the transformer of an RCA radio.
Bill Cahill
