Old Avo 8

Could it be a static charge on the cover? I have seen this to be an issue on some meters, especially if someone wipes dust off the surface.

WT

Yeah I have a Phillips analogue meter that does that a lot, rub the plastic "lens" over the movement and the needle rises, to settle again some time later.

My problem is definitely electro/mechanical in nature.

Cheers Ron(UK)

Is it in the meter movement itself? Sometimes, stuff flakes off of the metal yoke and is attracted ib between the moving coil and the surrounding piece to produce intermittent sticking.

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I cant see anything, the needle doesn`t jam or stop suddenly. It`s as tho there`s some kind of increased electrical resistance in movement somewhere, and a gentle tap gets it right again for a while, I thought maybe it was one of those common things that everyone knows about but me...

Ron

ISTR that some AVOs had a 'divide scale reading by 2' button - could that be faulty / intermittent. Or maybe my memory's faulty ????!

Regards Adrian Suffolk UK

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You can eliminate that by wiping the glass with a cloth damped with water with a little dishwashing liquid. However IME it's dust or dirt in the magnet gap. You may need to find a good meter repairman.

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N

We had hundreds of them in the Air Force, and that was a known fault, not common, but not rare either. Fixed by movement replacement, and that was the major reason for getting rid of them, the spares became outrageously expensive, ie you could purchase a lower-end Fluke for less than an AVO movement.

Barry Lennox

;-)

You can still buy a new Model 8 Avo. About 600 gbp.

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Holy crap in a bucket! I still have a Salford 50 Super Selectest which is much nicer looking but it's movement sticks too now. However you can buy those used for about US $50.

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N

Try gently tapping each component with a stick while watching the meter, you may have a resistor with an internal break or an invisibly cracked solder joint, happens sometimes.

If it ain't static, it could be just friction in its pivots, normally tapping with a pencil on its glass shall free the needle. If you are sure the problem is not in the meter movement it must be one of these series/shunt resistors which is common to all meter ranges. Is your problem persistent on all ranges and functions/Ohm/VDC/VAC/Amp ? Is your problem independent from needle deflection ? e.g at full scale/half scale/quarter scale ?

Is your meter still properly balanced, i.e. reading does not change when meter is rotated or tilted ?

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