Breadboard for OT

[dude]

I gave a brand new 18 watt OT that years ago squealed at first amp start up, l can't remember if I tried reversing the plates. On the bench my meter says it seems ok but I have doubts. I'm thinking l must have swapped the plate wires but being a Geaser...?
Anyway l can use a working amp chassis without removing it's OT, hook this one up "outside" the amp in place of it? Too dangerous?

[kagliostro]

.... hook this one up "outside" the amp in place of it?

Maybe using fuses .....

Franco

[sluckey]

Anyway l can use a working amp chassis without removing it's OT, hook this one up "outside" the amp in place of it? Too dangerous?

Sure. Unsolder the plate leads of the existing OT and tape the raw ends. Then connect the test OT primary plate leads to the tube sockets and connect the primary center tap to the same place the original OT center tap is connected usually B+ Node A. Now solder a speaker jack to the test OT secondary. That's all if there is no NFB loop on the amp.

If there is a NFB loop involved you will need to disconnect the feedback wire from the amp's speaker jack and connect that wire to the test OT's speaker jack. You will also need to connect the test OT secondary common lead to chassis.
 

[dude]

Thanks, can I leave the original OT's HVCT in place and just tap the testing OT CT there, it's A node of the B+? Maybe use the amps spk jack too, just take original secondary tap off attach testing OT sec and attach the neg feedback R then ground wire of testing OT to the original speaker jack. I guess no need to ground the testing OT as long as it's sec ground is hook to the jack.