This is to let you make a test output transformer for when doing service work on vintage/antique radios & similar circuits. All you will need is one very-cheap output transformer (avail from a variety of sources online for $10-20), two screws with aggressive threads like a short drywall screw or wood screw and 7 banana-plug sockets.

The output transformer I suggest using is meant for 70V PA speakers common in office buildings & hospitals. It is not designed to be used in this manner, but if you're only using it temporarily for testing small tube circuits it will work just fine. I have used it on everything from postwar AA5 sets to 8-tube TRFs with push-pull 45s. It is probably fine for up to maybe 10-watts, so don't expect it to survive a super high current audio amplifier for hifi or guitars. If you're looking for a test rig for a vintage radio, this will service most applications. If you're looking for a test rig for your KT-88s or 807s, this is not for you.

For SE (Single Ended) circuits, you want to attach B+ to the "0" terminal of the audio frequency side, and for the other wire (the plate) select whichever impedance is closest to your output tube's requirements (2k, 4k, or 8k). It does not have to be exact. You'd be surprised how far off the selection can be and the circuit will still "work." It will suffer in performance & sound quality the further off you go, but for a temporary test-rig it should not harm anything.

For PP (Push-Pull) circuits, you want to feed the B+ into the "4k" terminal of the audio frequency side, and for the two plate wires hook them up to the "O" and "8k" terminals.

I sized & shaped the banana jack socket holes to work with vintage American-made sockets that many hams & tinkerers already have in their junk box however the Chinese made ones on Amazon & eBay will work if you slightly file down the two flat sides of the socket before installing it.

There will be some wires on the transformer that will not be used. You can cut them back, wire tape or heat shrink them so they will not make contact with anything and ignore them. Use the pictures to see the wiring hookup diagram & wire color chart.