Pearl PS blowing fuses

[h_a]

I have the impression that something is really wrong; either you accidentially shorted the secondaries or the toroid may have a tiny internal short.

100VA are no problem; indeed regulation is better with larger toroids, so don't worry at all about that.

I would not use a larger fuse! Nor a soft start circuit!

You have nothing connected to the secondaries, so that's the lightest load the psu will ever be. Find your fault first before going further.

My advice is check your toroid with a multimeter. Check resistance of primary and secondary windings.

How come you measure 34V without rectifying? Are you using a true RMS-multimeter? Or are these peak values? Don't forget DC-voltage will be 1.42*RMS value.

Have fun, Hannes

[Paul Ebert]

I'm inclined to agree, Hannes. I certainly will not use a larger fuse. My DVM is not true RMS, in fact, it's about as cheap as you can get. But, I have access to good meters at work, so I'll check it out there.

But, in the interest of time, I think I will go ahead and order another, smaller, transformer.

I appreciate the help!

[Blues]

Originally posted by Nelson Pass
Likely the polarity of one of your primary windings is reversed. That
will do it every time.

Originally posted by Paul Ebert
....

To start, and until I can get parts in, could I simply use only one of the primary windings? ...

Have you tried the above like you described? Here's how you troubleshoot it to make sure it's just polarity reversal and not shorted toroid...

Without any load on the the toroid and with a fuse on one line of the primaries, and like you said..."simply use only one of the primary windings". If the fuse does not pop measure your secondary(ies). If the measurement is as advertised, unplug primaries and parallel second set of primaries. Plug paralleled primaries...if the fuse pops, unplug and reverse 2nd set of primaries. If the fuse does not pop go ahead and measure the secondaries and it should be the same as the first set of measurements. If the fuse still pops you have shorted primary windings...disconnect and buy a new transformer

allan