Up for sale here is this NOS vintage Knight power transformer, for the Knight S-755 amplifier. This has no ID on it except on the bottom, where it is marked 1005821 101403 (or possibly T101403). 1005821 means it was made by Northlake Transformer on the 21st week of 1958, and 101403 is the part number. This is a big one! I tested this with 120vAC into the primary, and I measured: Thick white wires 5.05VAC. Thick green wires 6.4v. Three thin white wires 409/409/818v. Each thin white wire to the one red wire 372v, 32v, 310v. Voltages always test a bit higher without a load, so it looks like this has a 5v secondary, a 6.3v secondary, a HV secondary of around 800vCT, and some sort of extra secondary with the red wire. This is a really nice transformer, and would work great for building a tube amp. It is guaranteed to work for you. If you know which amp this goes to, please let me know. Please see my pictures for details and dimensions. If you have any questions, please ask. I have more transformers and other vintage electronics listed–feel free to take a look!