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Old 10th Feb 2018, 3:25 pm   #1
linescan87
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Default DC AVO Minor.

Going through stuff in my friend's shop I came across this. It was dropped in by a lady a few years ago who was having a clear out.

She was going to throw it in the bin!

John Joe.
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Old 10th Feb 2018, 4:54 pm   #2
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Default Re: DC Avominor.

That's the first version, with smooth sides not stepped sides, if I recall correctly. I wonder if it's got a mouldy cell inside!

Would be interesting to know the serial number on the scale plate below all the other text. Coincidentally I dug mine out the other day and it is quite early- 1034-93 (Meter number 1034, September 1933)

Mine was found some years ago in a skip behind a school.

You actually have 6 DC voltage ranges there- 12v, 240v and 600v DC ranges are hiding: they are obtained by using the 6mA terminal in place of the + terminal. On some of the instruction plates this information is missing- and I think the meter pictured is one of those.

Dave
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Old 10th Feb 2018, 7:47 pm   #3
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Default Re: DC Avo Minor.

Hi Dave,

Luckily there is no cell inside. I won't be back at the shop till Tuesday, I shall get the serial number then.

Sadly the glass is cracked but I may get a piece cut, a local gazier often supplies small pieces for radios etc.

Cheers,
John Joe.
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Old 11th Feb 2018, 3:00 pm   #4
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Default Re: DC Avo Minor.

The glass in the DC Avominor is the thinnest of them all, it's pretty much the only part of the whole thing that's under-engineered. Opinion differs on the best adhesive, (some use a type of mastic or putty in case it ever needs to be removed again) I use 5 minute Araldite, but it is a pain to remove if you ever have to replace the glass a second time. The trick with Araldite is to err on the side of too little glue rather than too much, blobbed at strategic places- i say this partly because there are only two clips holding the glass in on this model, both at the top. Superglue is not suitable because white traces can creep across the surface of the glass afterwards and you end up with what looks like mouldy glass.

(Too much glue on one of my later meters, actually stopped the glass flexing with the carcase, and it the cracked without external provocation. An isolated incident, i imagine the crack instigated at a flaw in the edge.)

When soldering/de-soldering anything try to go in perpendicular as there isn't much room and it is ridiculously easy to burn the sides of the carcase!

Dave
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Old 12th Feb 2018, 9:30 pm   #5
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Default Re: DC Avo Minor.

Thanks for the advice Dave. I shall be seeing the meter tomorrow and will get the serial number then.

John Joe.
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Old 13th Feb 2018, 1:12 pm   #6
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Default Re: DC Avo Minor.

Serial number 6619-107.

John Joe.
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Old 13th Feb 2018, 10:07 pm   #7
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Default Re: DC Avo Minor.

Looks good so far, doesn't it? - one peculiarity to watch for when in use (or calibrating) is to not have your fingers resting on the front facia. The terminals are almost flush with the front on some DC Avominors and it is possible to skew the readings just by lightly touching one or more of the terminals, The safety of the high voltage ranges was, and is, limited by this design feature!

I have 2 of these, both of which i originally tested and then put to one side having considered them to have terminally damaged movements. When i got them out of their box at the weekend and carefully manipulated the movements back and forth, they both started to show signs of being ok.

Dave
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Old 13th Feb 2018, 10:13 pm   #8
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Default Re: DC Avo Minor.

Quote:
Originally Posted by linescan87 View Post

Sadly the glass is cracked but I may get a piece cut, a local gazier often supplies small pieces for radios etc.
If you get some thin 'picture glass' (I save bits from broken pictures, you might even find a cheapo frame with some glass in it in a charity shop) then it will cut with scissors (!!) if you do it under water. Weird but true... I've done it for vehicle ammeters, speedos etc.
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Old 13th Feb 2018, 10:34 pm   #9
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Default Re: DC Avo Minor.

The Universal Avominor tends to be around 1.5mm, the DC Avominor is around 1mm if memory serves correct. I don't know how much leeway you have for going thicker. Not much, i suspect. Cutting glass underwater.. Wow. I hadn't heard that one!
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Old 14th Feb 2018, 10:17 am   #10
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Default Re: DC Avo Minor.

I have never heard of cutting glass with a scissors before, I will have to give that a try!

I will let you know how I get on with it, but it will be a few weeks. For now it's on display in my friends shop window as a curiosity!

Cheers,

John Joe.
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Old 14th Feb 2018, 12:50 pm   #11
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Default Re: DC Avo Minor.

This one is around the 37 thou. mark, 0.95mm thick, and a very unforgiving shape to cut. Best of British, if the rest of the meter is ok it is worth a go.. or several goes!
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