The filament power supply

The power for my filament comes from a rewound microwave oven transformer (MOT). There is loads of info' online about doing this so I won't go into it here. I'm getting about 6v tops out of this one.

There is also a 'dimmer' suitable for use with inductive loads. It came from a company called 'Brocott'. I got it through Ebay.co.uk. You can see the little VR going through the lid of the box to vary the power. (Its a really crappy VR wobbling all over the place. I may have to replace it with something a bit more substantial. Saying that, it doesn't matter at all for the brute force output.)

I'm going to put an illuminated power switch and a 50 amp ammeter to keep an eye on the power without burning my eyes out watching the filament!

Anyone know if you can convert a DC ammeter with external shunt to AC? I've gone and bought the wrong one!