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Old 22nd September 2009, 05:44 PM   #1
bigwill is offline bigwill  United Kingdom
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Angry Broken VCM163

I have an AVO VCM163, but the coil movement for the Gm meter is damaged from a knock at some point and probably needs replacing. I have no idea if it's possible to get a new movement

I am very, very annoyed by this (avoiding swearwords) as I saw someone selling replacement movements on eBay a while back but now they seem impossible to find

Is there anything I can do? Can I just put in another movement?

Help
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Old 23rd September 2009, 03:29 AM   #2
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I don't think you can purchase a new from from AVO since they are gone. There is a forum with a thread about this model where you might ask.
http://www.vintage-radio.net/forum/s...078#post273078

If this were mine, I would discover as much as I could about the meter movement. Manufacturer, model/style and full scale value to begin with. From the pictures I've seen it resembles a Weston, but this is just a guess. Once you know more about it, you can look for a similar style of movement in a milliamp or voltmeter and replace the scale or card with yours.

Hopefully your meter doesn't have anything special about it like the Hickoks which have a magnetic shunt on the outside rear.
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Old 24th September 2009, 10:51 PM   #3
disco is offline disco  Netherlands
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Finding new or used will be very hard. Can't you have it mended?
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Old 25th September 2009, 08:07 AM   #4
EC8010 is offline EC8010  United Kingdom
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There's nothing special about the gm meter, it's a standard 50uA movement. Find something of a similar size and it will do. However, if you're lucky, yours may be fixable, but you need a delicate touch. Sometimes, the moving part can be sprung away from its bearings. Take the meter out of the case and remove the front panel to expose its innards. Use some jeweller's screwdrivers to loosen the bearing and its locknut, then gently move the coil and its point bearing back into place and gently tighten the bearing and locknut. Leave a little play in the movement - otherwise there will be too much friction. This has worked for me on previous meters and you have nothing to lose.
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Old 25th September 2009, 10:45 AM   #5
bigwill is offline bigwill  United Kingdom
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Quote:
Originally Posted by EC8010 View Post
There's nothing special about the gm meter, it's a standard 50uA movement. Find something of a similar size and it will do. However, if you're lucky, yours may be fixable, but you need a delicate touch. Sometimes, the moving part can be sprung away from its bearings. Take the meter out of the case and remove the front panel to expose its innards. Use some jeweller's screwdrivers to loosen the bearing and its locknut, then gently move the coil and its point bearing back into place and gently tighten the bearing and locknut. Leave a little play in the movement - otherwise there will be too much friction. This has worked for me on previous meters and you have nothing to lose.
I may try this (or ask someone who is good with this sort of thing - I know someone who can mend mechanical watches). It does work - it just gets stuck halfway along the scale. It might just be a case of a little fiddling

Thanks for the suggestion
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Old 25th September 2009, 12:02 PM   #6
disco is offline disco  Netherlands
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Quote:
Originally Posted by bigwill View Post
I may try this (or ask someone who is good with this sort of thing - I know someone who can mend mechanical watches). It does work - it just gets stuck halfway along the scale. It might just be a case of a little fiddling

Thanks for the suggestion
Sometimes, when cleaning too much , plastic parts can build up static. The trick to overcome this kind of 'sticking' is applying a small amount of carbon dust, from a pencil for example. The static will diminish through the conducting layer.
On the other hand the problem might be caused by mechanical troubles. Open it and inspect D)
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Last edited by disco; 25th September 2009 at 12:10 PM.
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Old 21st July 2011, 02:36 AM   #7
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Hi,----is the FSD 50uA for certain? Do you know what the coil resistance is for the VCM MKIII? Please help if poss,
Thanks,
Mike
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