potted my toroid

[tedmich]

got a Toroid Corp. 205.5076 (260/13.5/7.5VAC) PT for $93 off the list price... plan to use it in a preamp, either a Bad Cat xtreme tone, or a Deliverance (from SloClone)


Potted it into a SS coffee canister lid I got at target:


I put brass bolts and threaded inserts (1/4"-20) in the middle, and sorbothane pads on the base


the center bolts are (nonmagnetic) SS, and the dome conducts well through them (<1ohm) is this a problem? Will I need to isolate it from the chassis/ ground?

[Enzo]

Doesn't matter if the bolts are magnetic, all that matters is if they conduct current.

We have mentioned this elsewhere around here. If you bolt a toroid into a chassis and then put a lid on the chassis, if the bolt touches both lid and floor of a chassis, then it represents a turn on the transformer. In that case a single SHORTED turn.

If your metal lid conducts to those screws, then you better not let the screws and shell both touch the chassis.

[Steve Conner]

Yup, you had better make sure the dome doesn't touch the chassis. The rubber feet you put on should already take care of that.

Alternatively, use nylon washers to isolate the bolts from the chassis. Heck, you could even do both.

As an aside, potting the toroid will have reduced its capacity to get rid of heat, so you'll have to derate it a little, maybe 10, 20%. Shouldn't be a problem in a preamp.

I like this idea by the way, I have a huge ugly 500VA toroid that I want to use in a high-power bass amp, and now I'm thinking cooking pots

[defaced]

Deliverance (from SloClone)

Good choice. If you haven't checked the thread in a while, I uploaded a turret layout the other day. Should be on the last page (13?), I'm the same user name on each forum.

Are you planning on building the whole amp with this transformer or just the pre?

[tedmich]

Doesn't matter if the bolts are magnetic, all that matters is if they conduct current.

We have mentioned this elsewhere around here. If you bolt a toroid into a chassis and then put a lid on the chassis, if the bolt touches both lid and floor of a chassis, then it represents a turn on the transformer. In that case a single SHORTED turn.

If your metal lid conducts to those screws, then you better not let the screws and shell both touch the chassis.

Thanks!
I remembered this from previous posts, I think I'll just use some glass filled nylon cap screws (2 x 1/4"-20 will be plenty strong) and attach a ground strap inside the rim. This PT will only be enough for a couple of 12ax7s (260VAC/0.1A) so its just a preamp