Can anyone suggest someone who can recondition these old ammeters?
My No75V has just packed in and since I think it is an original one I would like to get it fixed.
cheers
Dave
Hi Dave, these are easily tested to find the problem and disassembled to fix. I have fixed a couple from spare parts from other broken ones. First find out what is wrong, they are basically simple on operation so generally not many things can go wrong, usually the pointer is stuck or the coil is broken
First is to test continuity, making sure the coil is not broken, sometimes the thick copper wire (coil) can break way from the connecting post, this can be re-soldered back on. Remember connecting a battery alone would not show anything as you are measuring current not voltage. To test continuity you can use a multi meter or by connecting a battery and bulb in series with the ammeter. By doing this you can also check the accuracy to see if it is working properly. For example if you use a 12V battery and 36W bulb the ammeter should read 3 amps. Remembering from school, Amps = Watts (bulb rating) / Volts (battery).
Also check that the pointer moves freely and does not stick. Centralising of the pointer on the scale can be achieved by slightly rotating the rear fixed magnet.
More difficult is to assemble different parts from different ammeters, e.g. a coil from one and pointer mechanism from another. You would need a bit of patience with this as the pointer mechanism is quite delicate and will not necessarily move freely without touching in a different coil. I found I had to adjust the shape of the coil a little to make it work.
You should have a go yourself, if you are careful and not heavy handed you can not do much more irreparable damage then if it is not working already.
I would not recommend you remove the actual pointer from its support housing though as if it very delicate.
hope this makes sense and is of help
regs