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Old 20th Jul 2021, 4:02 pm   #4
pmmunro
Octode
 
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,435
Default Re: AVO 8 Mk5, should i attempt repair, or send it?

It's a good sign that the pointer still swings freely, as long as it is not too free, indicating a lack of damping. If the pointer swings without the usual damping, that would indicate that the movement is either open-circuit or disconnected from the universal shunt chain.

It would certainly help if you had the service manual for the Model 8 Mk V. If you can't find that on-line, let me know through a private message and I will send it to you. Once you understand the curcuit of the meter it will be much easier to find the faul(s).

Basically these meters are 37.5 micoampere instruments with the rest of the circuits to give the various ranges calculated around that basic movement. If you can verify that the movement is operational, it should not be too difficult to find the trouble.

These meters use flexible printed wiring which has to be folded back to access the movement. This printed wiring is quite fragile and the tracks are easily broken if not handled carefully. Broken tracks can be by-passed and it is possible to make up a loom using conventional wiring to replace the print.

PMM
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