OT - AVO help needed.

the weekend. I fitted it with a new 1.5 volt "A"

found an AVO meter that didn't work!

continuity & still nothing.

have one of course. It seems to me from reading

correct in this & would others here expect it to work

Just for you Kim I went out to the shed & dug out my standby Avo Mk8 & a 1.5v battery. The 1.5v powers the lower two resistance ranges and the

Thanks Dave . S-o-o-o, I was right? It ought to work on the lower ranges with just the 1.5 battery fitted?

Regards,

Kim Siddorn

That's my recollection. First thing I would check is the overload contacts.

Tim

Only on the resistance ranges. Failure to get a response on any range points to something pretty fundamental like a fried movement or (hopefully) failure of the overload device to reset correctly as Tim has suggested.

NHH

I think I've seen a tip to "fake" the 15v battery with a stack of button cells.

BugBear

Yes - iirc that is using the principle of how the early high voltage (48v?) portable radio batteries were put together.

Regards Pete

That should work fine. Other ways might be to series-up a few rechargeable NiMH two- or three-cell printed circuit board mounting memory battery packs, or even get a 10-AA-cell battery holder and clip from Maplins, and run wires into the meter, if you don't mind an external battery pack.

Hmmm - we've got a couple of Avo 8s around the place; I might try the memory-battery version, if I can find enough of them in usable nick on old PCBs (and the tuits to do the job...).

The battery is still available. Google for BLR121

In message , Roland Craven writes

Crikey - between six and nine quid a copy, give or take. Ah well, at least it's still an option...

Yup, spent many a happy hour in the Standards Room at Mullards doing the calibration slips for those and the earlier Mk7.

If you look on the AVO/Megger website, I think there is a section with downloads of manuals.

Peter

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PA> wrote (snip):

PA> Yup, spent many a happy hour in the Standards Room at Mullards doing PA> the calibration slips for those and the earlier Mk7.

And I may have used some of those very meters after the move of Thorn EMI Radar Division from Hayes to Crawley!

nickh=== Posted with Qusnetsoft NewsReader 2.2.0.8

If anyone feels the need of an AVO8, I've got a spare one, fairly late model, no leads, which could be swapped for a modest supply of beer tokens. I'm keeping the one I was given as a 21st birthday present. Also have an AVO 40 which was my father's, I think he got it ex- ministry in the 1950s.

Tim

Small World!

I was there in the early 1960's, the guy that ran the Standards Room was Fred Fisher, lovely man, could use and talk you through any of the test gear that the factory used.

They had a large Frequency Standard which was locked to Rugby LW radio station IIRC, and a host of other stuff, but the main business was the meter test and repair/calibration and the various bits of radio test gear.

Peter

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The battery is only used for resistance readings. It should work on the voltage ranges without a battery fitted! Peter

That's what I thought. Summut very basically wrong there I think - I bet it's a dry joint, it usually is.......

Thanks to all that replied.

Regards,

Kim Siddorn

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Kim, I tried to reply to the email you sent me off-group, but it bounced back. Can you email me again from a working email addy? Thx, Pete

I once saw an Avo model 7 left connected across 400 volt dc busbars, switched to resistance range when the power to the cubicle was switched on. Result - lots of smoke, soot inside the glass dial and a non-working Avo! Pete

This thread has brought back some memories.

I spent many hours repairing and setting up Avo's during my time at BAe Brooklands in the mid 1980's. We had hundreds of them, they came in for calibration every six months and any that didn't make it came to us for repair. A completely dead one would be pretty unusual. As someone else has already mentioned, the overload cut-out mechanism would be the best place to start. The cut-out was a cunning piece of mechanical trickery that relied on the acceleration of the pointer to make it trip. They could be an absolute swine to get right, so that they weren't over sensitive but would still trip out on overload. There were parameters that we used to test this and we would subject the meter to x times (I can't remember how many) to ensure that it tripped or didn't trip. I remember part of the adjustment task was hand polishing a little table that the cutout lever pivoted on. All work was carried out with Brass Screwdrivers to ensure nothing magnetic got anywhere near the movement.

You mentioned this this was a 1980 unit. Can you advise what mark this is? My memory is now going back over 20 years, but I believe that with the Avo 8 Mk 5 (or may be 7) , they brought in a flexible plastic PCB to replace the point to point wiring between components. This move was viewed with disdain as it made them a swine to repair and they were prone to cracking solder joints on the PCB which was curved around the components.

We only had a few of the new ones, the majority were earlier 8' and lot of

Stuart

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