AVO Meter problem

  johnlecarre 17:59 04 Sep 03

This may not be the right forum for this but on th offchance that one of you more experienced (older!) readers may be able to help, I am short of ideas.AVO Meter model 8 mark IV, ohms scale will not zero adjust,goes to about 5K only.Other two ohms x100 and ohms/100 are OK.Checked leads,batteries and adjusting pot, all OK. Any clues?Many Thanks.

  -pops- 18:09 04 Sep 03

Possibility it has been connected to a powered up circuit whilst set on the resistance scale.

(Didn't know there were any Avo's still in use)

  Pidder 18:20 04 Sep 03

Checked the switch contacts?

  Megatyte 18:26 04 Sep 03

Sounds like (a) resistor/s gone open circuit.


  hssutton 18:32 04 Sep 03

It's doubtful that it's due to being connected to a voltage, this would normally blow it completely.

What I did recently to overcome this problem, was to lift the unit out of the case and on the zero adjust pot. carefully drill a tiny hole in the casing and then spray in a small quantity of switch cleaner.


  Rtus 19:06 04 Sep 03

If you want a link to someone who's repaired hundreds of em.. Give me a shout (VIA the yellow env < )

  johnlecarre 20:23 04 Sep 03

Thanks for the feedback guys, nice to know people still remember the 'Rolls Royce' of test meters.I know everyone uses digital meters these days but AVOs are still as accurate (except mine at moment!)if you know how to read them.I used a slide rule at school,just as good and fast as a calculator, I'm not that old either, 48.
Thanks again.

  broggs 20:43 04 Sep 03

Ahh the good old Avo....served my apprentiship as a Hi-fi engineer using the Roller.Many a time the cut -out nearly hit the roof ;-)

  ton 21:29 04 Sep 03

Switch contacts or low battery voltage would be my first thoughts, or a dry joint somewhere.

  fred 21:43 04 Sep 03

I remember the nightmare of replacing the cracked case of one. Brilliant machines.

Could it possibly a 'cooked' resistor rather than a blown one thus altering the value significantly?

  graham√ 21:59 04 Sep 03

Analogue meters still have their use! BT engineers use them to estimate visually the line length to a disconnection fault using the reverse button. The same means can indicate if a socket or phone is present. Can't do that with a digital!

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