Failed toroidal transformer

[Neale]

Clive,

Everything I've read about toroidal transformers seems to say that the primary winding resistance is pretty low and mine is about the same as yours. I wouldn't trust my digital meter to fractions of an ohm! However, with just the transformer connected to the mains (all secondary windings disconnected) it blows the fuse. Maybe a shorted secondary? I've checked the two bridge rectifiers in the PSU and they look OK, the smoothing caps look OK (or at least, not short-circuit), and the secondary side fuses haven't blown. Points to a transformer fault to me, but there's still that nagging doubt...

Anyway, I've ordered a 55+55V from Rapid who have a better price than Airlink, free delivery, and probably arrive sooner as well. Two windings in parallel and that should do the job, and only a couple of volts down on the original.

Thanks for taking the time to measure your transformer for me - much appreciated.

[Clive S]

Neale Are you happy with 55V as you are getting close to the limit as that will give you about 77V DC. Just checking.

[ptjw7uk]

Did you remove the secondary's from the rectifier as a dud rectifier will cause the primary fuse to blow!

peter