AVO Multimeter survey

[Barnmead]

Another one for the darabase
Heavy Duty Avometer with case and leads
15735-463.A.

[duncanlowe]

I must be having bad luck. Just bought a MkIV and no sign of a serial number on the side though there's evidence of where the label must have been. Seems in nice condition (which is why I bought it) and comes with a decent condition leather case, with leads probes and clips. Both batteries still in, no leaks although I think 'fumes' from the 15v battery have tarnished the surface of its terminals.

[MonEvans]

I have what I assume to be a 1989 model. It has the two leads/probes. There's evidence of corrosion so I think there must be batteries inside. The number is 48316 89/671

[Superscope]

MonEvans,

Thanks for the Serial Number.

I am assuming there is a typo in your Serial Number,
and I'm guessing it is actually 48316 84/671 or 48316 84/6/71,
please let us know if that is not the case.

This will make it a Model 8 Mk IV from June 1971 and
that fits in perfectly with the other Numbers we have.

Again, I am assuming due to the Serial number format, that your
Meter has the serial Number on a sticker on the right side.

Can we ask if it has the Black or a Green/Grey housing?

If it is Green/Grey, it will likely have cracks in it eminating
from one or more of the Screw holes. It's quite rare to find
a completely undamaged Green/Grey Housing.

The Model 8 Mk IV was only in production until late 1972.




Ian

[factory]

I've saved an AVO Test Set Multi-Range No. 1 from becoming another lamp foot or timepiece.
And unlike the last AVO 8 I acquired (with O/C meter), this one appears to be functional & no leaktubes left inside , I've not checked the accuracy yet though.
Not 100% sure if the year is 73 or 75, S/N is 14228-10-7x


David

[Superscope]

Your Serial Number should by all accounts be from 1972, but it's very difficult
to turn that uncertain number into a Two !

Could have been delayed out of the Factory due to a quality issue and been
given a later Date Code.

I have seen a few Numbers slightly out of sync with the Date Codes, but it's
quite rare.




Ian

[RichardGM]

My job and my colleagues' jobs gradually changed to involve less and less lab work until eventually the bosses decided to close the labs completely. Staff were invited to bid for the redundant equipment and I acquired a few items including an Electronic Avometer Type EA 113. What I assume to be its serial number is just four digits: 5891. I can't see any other identifying numbers on the outside or under the bottom cover that you remove to get at the battery.

[Superscope]

Well, I'm surprised nobody commented on the Model 1 on Ebay yesterday.
I had to have a double take when I first saw it.

It went for well above my pay grade, but I did get the Serial Number
and the best Photos I've seen of a Model 1 so far.

Congratulations to the new owner, hopefully it has fallen into a safe
pair of hands.
I noticed the pointer was bent and well off the Zero position so somebody
has probably been inside at some point or heaven forbid it had a hard drop.



Ian

[Sinewave]

I've been watching it.

Lost for words, someone has paid well over the odds for something in woeful condition, fools and money.....

[Superscope]

Not sure I would be quite as hard as calling it "in Woeful Condition".

I thought for the most part it looked pretty good to excellent, especially
bearing in mind it will be nearly 100 Years old now.

I suspect it will probably sit in somebodies Collection and not be fixed,
which might not be a bad thing.

Lets hope inexperienced Hands don't get to meddle with it and the new
owner knows of its historical importance. I suspect they do hence the price paid.

The Movement was clearly damaged for whatever reason, but I have
successfully repaired a Movement that looked far worse on a Model 5, so there
is always hope the Meter could be bought back to life in the right Hands.

If it was bought by somebody on the Forum, I doubt we will ever find out,
which is the real shame as a thread on a Model 1 repair would be very
informative.


Ian

[Sinewave]

Condition ratings vary over price, I suppose. For £20 it'd be ok, but for over £500, seriously, wow.

[Aitor Eneko]

I did not buy it. I did not see it. I would not pay 500 pounds. Congratulations for the winner. Is it possible to see the photos?

[Superscope]

I didn't have any good Photos of a Model 1
The Photos were were informative, at least for me.

As Dave said, now that this one raised its Head it might encourage others
to suddenly appear. We can hope.

Although it would be very nice to have one and unfortunately I don't,
the Model 4 and 6 are actually much rarer.



Ian

[George Cooper]

I have a Avo 8 Mk2 No 66779-C-1057 and a Avo 8 Mk6 No 1214 M 0218

[barrymagrec]

Originally Posted by RichardGM

My job and my colleagues' jobs gradually changed to involve less and less lab work until eventually the bosses decided to close the labs completely. Staff were invited to bid for the redundant equipment and I acquired a few items including an Electronic Avometer Type EA 113. What I assume to be its serial number is just four digits: 5891. I can't see any other identifying numbers on the outside or under the bottom cover that you remove to get at the battery.

The serial number on my EA113 is only 3 digits: 119.

Must be quite an early unit, doesn't work though and the circuit board is not in great shape.

[Julesomega]

I have the Avo 8 Mk II; Serial No. 9840.C.364.D

The 15V battery was replaced with an inverter operating from the D cell, with an on/off switch, too long ago to remember and before I could have contemplated designing such a unit, so I'm wondering was there such a modification published sometime in the 60s?

Looking today I find the BLR121 batteries are readily available at sensible prices. The beauty of using a battery is that no power is used as long as you are not taking a reading on the Ω × 100 range

[jez_145]

Originally Posted by Julesomega

The beauty of using a battery is that no power is used as long as you are not taking a reading on the Ω × 100 range

Yes, absolutely right. The AVO voltage convertor VC1, for instance, always seems attractive in that it allows all the resistance ranges to run off the single 1.5V cell. But, it's "on" all the time. Even though it uses very little current when idle, the cell will eventually drain to nothing and that's when you can expect leakage to occur. The VC1, is great if the meter is in constant use. Not so great if only used occasionally.

Morale: if you've got a VC1 and haven't used your meter for a while, check it RIGHT NOW and get the cell out. In fact, even if you haven't got a VC1, do this anyway!

Jerry

[The Philpott]

Post 2897:- Fair comment. The quiescent 'bleed' from the D cell to the VC1 box is only a few uA, meaning a matter of years for a healthy cell to be depleted...but as we know some alkalines (particularly Duracell) have a habit of premature leakage, and the electrolyte is much more venomous than that of a Zinc Chloride.

The VC1 is rated for 15v @ 90uA maximum, but in practice the high resistance range uses much less. It is sized for the Model 8/IV onwards i think, slightly overlength for an 8/III but can be inserted if the grub screws are removed from the output contacts. The composite copper/plastic sheet conductor for powering the VC1 is the weak point; when i get round to installing one i won't be using it...too fiddly.

I am now relying on BLR 121's restuffed with (five) Lithium Metal CR1025 and taped back together. (I covered the mod. elsewhere, the diameter is too small meaning they had to be put in a plastic tube first)
I quite like this particular mod. as once you've selected the spring/spacer/tube the procedure is repeatable so long as CR1025 is still an available size.

A quick health check is of course to set the Avo to it's resistance ranges and see what voltage is available across the terminals. (Not foolproof though)

Dave

[The Philpott]

Further to what Jerry has mentioned, there's one other source of quiescent drain (just about) worth mentioning, and that's on the Avo Model 7. It appears that at some point in WW2 a mod. to the basic design was carried out which biased the rectifier slightly for AC readings using a trickle from the 1.5volt cell..thus ideally when idle the meter is not left at an AC setting. (The current is very minimal, and is typically indicated by the needle nudging upwards very slightly)

Dave

[Bandicoot]

Just added info to the database, as have refurbed a model 8 V which had some battery leakage damage to the flex cable, so replaced with hard wiring per info from this site, most useful and thanks to the contributors. Alan.