Repotting the transformers
I got my potting compound yesterday, so I got the new power transformer potted. It took more compound than I anticipated so I held off on potting the output transformer. Once I have more compound I will pot it too. I am using Hammond transformers: a P-T274BX power transformer and a P-T1650G output transformer.
Transformers w/temporary base plates
I decided to try something new while potting these transformers. I wanted to be sure that the transformer leads were bundled and properly positioned during the potting process so that they would line up with the holes in the amp chassis. To do this I took two pieces of 1/16” aluminum and drilled holes in them to match the holes in the chassis. This allows me to pull the leads through the large hole and attach the aluminum plate to the transformer can, thereby ensuring that the leads are properly positioned while the compound sets up. It seems to have worked fine on the power transformer so I’m sure it will work okay on the output transformer as well.
I’m looking forward to getting the power transformer installed so I can start working on wiring the power supply.
NICE JOB AND COOL JIGS . WHERE CAN I FIND SOME POTTING COMPOUND I WOULD LIKE TO FIX A B15 I HAVE BEEN HANGING ONTO FOR YEARS WITH A BAD TRANSFORMER
THANKS
DAVO
Hi I have to replace a B15S OT and I was wondering if you could tell me how you got the old transformers out of the cans. And also what is the potting compound you used to repot?
thank you .
James – I set the transformers right-side up on an old metal baking tray and put them in the oven one at a time. I think I had the temperature set at 450F – 500F. The old tar compound starts to liquefy and drain into the tray. I remember using an old oven mitt to grab the can but I don’t remember what I used to pull the transformer out. The PT may have just dropped out but I remember the OT was a little smaller and they had used a couple wood shims to hold it in the can. It was harder to get out and I probably used an old pair of pliers or something similar to pull it out. I used a product from MG Chemical called 832TC. I think I used the 450ml size and had to use 2-3 of them for one transformer. I think 2 should have been enough but one of the sets had settled badly and I had trouble getting all of it mixed.