View Single Post
Old 21st Nov 2017, 12:05 am   #3
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default Re: AVO Model 40 Multimeter

What year is it? If it's an early one:

The 10k ohm range relies on a resistance of around 180 ohm.. a photo would be a help as i expected this 180 ohm to be a winding but are you saying it's a component resistor.?

The 1000 ohm range uses a winding of around 15 ohm. Although it's failure to function could also be a switching problem. There's an extra pair of contacts that have to close on this particular range, as i recall.

There is (i think) a third winding on the resistance board, which is about 1 ohm (quite a thick one)

The high range (100,000 ohm) can be a nuisance as the Q potentiometer has inherent problems especially in old age- the Q shaft must have continuity with the cleverly shaped brass orifice in the facia. Also there is a little arrow shaped precious metal prod in the end of the Q shaft, and it's not unknown for this to be slightly loose, which can affect all 3 ranges. I posted some images re. this issue so if you search under 'Q shaft' or something like that you will find them in the avometer survey thread, or test equipment thread.

Dave
The Philpott is offline