Quote:
Originally Posted by pmmunro
Would you like a replacement shunt board which has been salvaged from a scrap meter?
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I received the shunt board that pmmunro very kindly sent me and swapped it over for the burnt one, I tested the Avo on the volts range with a 9V battery and it still read about 2V too high, this didn't really surprise me as the burnt shunt board is for the current ranges and needed replacing to use these, from the manual too high a reading is down to the swamp resistor, now I don't know what it looks like or where it is, but as it's in series with the movement I disconnected the wire from the movement and wired in a small variable resistor which I adjusted to get the meter reading correctly, measuring this after correcting the readings gave a resistance of 1676Ω which I'll make up from a couple of fixed resistors. I'm a little puzzled as to why the swamp resistor is so far out, the total resistance of the movement + swamp should be 2667Ω and I've had to add 1676Ω, I can see a shunt being burnt out from a current overload but the swamp only has to carry 37.5μA.
I've just tested it on DC up to 400V, AC up to 300V and DC up to 2A against a Fluke 73 and any error is not much more than the Avo's needle width.
So many thanks to pmmunro and all who helped me to repair the meter.
John