(Avominor) Protimeter 545-558

[The Philpott]

I did not expect to find one of these, it includes the leather case but lacks the probe/leads assy. It looks like the probe points are around an inch apart from reference images, but if anyone could confirm that would be helpful.

I concur with previous observations that it has all the hallmarks of being made by ACWEECO as a special, then passed to Protimeter. (The hammered paint finish on the rear looks identical to that on certain metal cased avometers of the period, and the modified black card cover for the innards is very tidily made)

Micheal advised some time ago that the movement on these consumes 339 or 340uA, and speculated it could be a Model 2 movement shunted up from 250uA. Highly likely.

The switch legends are RESET and USE on this model (not CHECK and TEST which may have been abandoned due to it's ambiguity)

The variable resistor is jammed somehow but the 30v battery compartments are relatively clean. No photos yet but i'll crack on with that at the weekend.

I could actually use this- up until now my only 'damp meter' has been an Avo Model 8/III on ohms x 100 range- which i would imagine is far less sensitive.

Dave

[Superscope]

A rare find Dave for sure,

That's only number Six in the Log.

Definitely an Avo produced offering, but very short lived.

All Protometers so far, including your new one are dated between 1956 and 1958


Ian

[The Philpott]

There's 15.5mm width available in the battery compartments, so it's likely the best choice is CR1220 or CR1225. There's enough length in one battery compartment to house twenty CR1225 cells while shorting out the terminals in the other compt., provided the C of G doesn't move too far to one side.

The siezed variable resistor is due to the wiper having been badly bent away from it's winding, for reasons unknown. It'll need to be desoldered off the shaft and replaced with a spare once the movement and switch assy. is taken out. An annoying job on a standard meter, but there's much less innards in the Protimeter so it's less of an issue.

Before i reassemble i'll check whether the resistance winding matches up with factory standard for Model 1 or 2 Universal Avominor. If it's neither, extra care needed!

The damping of the movement is indeed very reminiscent of a Model 2.

Dave

[Avo Mk8]

Is this the same beast (I don't mean the actual one - I mean of similar age?)
https://www.ebay.co.uk/itm/374621275315
Complete with the probe!

[The Philpott]

That's the one. It gives me a better look at the probes, thankyou.

Dave

[The Philpott]

Helpfully, an ebay seller has measured the distance between the probes on his example, and advises it is 15mm.

Dave