benadrian wrote:[How far from non-zero should it be. I measured those the other night, and I think the resistance measured about 10 - 20 ohms, which seems low to me, but wasn't technically a short.
This sounds reasonable, I think. I'm not so sure, but IIRC I've measured good transformers with resistances less than 10 ohms on on of the windings. I know I've also seen a PT with the rectifier heater winding reading 0 ohms, and fuses blowing immediately. This was, AFAIK, caused by a rectifier tube drawing too much heater current.
If it's blowing fuses with no tubes in it, that immediately suggests a short somewhere. It's not that there's a cap that's fucked up, since they don't even enter the picture until *after* the recitifer gives you your B+. It's something between the plug and the rectifier socket. It could be shorting to ground somewhere, or it could be that one of your windings is fucked. At least I *think* that's how it works.
While you're at it, check the power plug, make sure that you've got one pin showing up on the place the white wire connects to the fuse or power switch or whatever, and no others, and the second pin showing up at the end of the black and no others, and that the ground pin on the plug is showing 0 ohms or damn near it when you check the transformer lug that the green wire is attached to, or a very low resistance like (I'm not positive here) 0.05 ohms or something clearly non-zero, but less than 1 ohm if you check a random spot on the metal chassis.
An again, I'm pretty sure the normal resistance of PT or OT windings can be surprisingly low but non-zero. Like 5 or something. The thing is, if it's zero, you know exactly which winding is fucked. None of them should ever be a short. On any transformer.