Heavy Duty Avometer Mk5

[threeseven]

I bought this some time ago but the seller didn't heed my advice on packaging so consequently it was damaged in transit, lower case split on 2 corners on one side. Very annoying as it was otherwise as new

Like this one,
http://www.radiomuseum.org/r/avo_avometer_mk_5.html

So I kicked it into the long grass until the disappointment wore off!
Apart from the split case I've noticed the meter can't be mechanically set to zero and doesn't swing smoothly. It seems to bounce off the left hand stop after rotating the case to observe the swing action. Any idea's on why that might be?
It is puzzling why Avo bothered to make this meter, apart from being simpler to operate and slightly smaller than a 7, to which it's similar in sensitivity, I can't see much advantage. It was obviously a small production item as the resistance panel is a piece of veroboard!
If anyone knows where I might find a NOS lower case I would appreciate it.

[Phil G4SPZ]

By all accounts, this model was designed at the specific request of the Great Western Railway in the immediate post-war period, and had ranges more suited for railway signalling and communications work. Most date from 1948 onwards and the Mark 5 is said to be the most common.

Phil

[pmmunro]

Threeseven,

The Heavy Duty Avometer was originally designed around 1947/8 at the request of the Great Western Railway although it seems likely that when delivery began that had become the Western Region of BR.

The first versions had a die-cast aluminium front panel and case and were heavy both to carry and in the construction. The ranges were selected to suit railway Signal and Telecommunications (S& T) requirements. It must have been considered a useful design because a commercial version was also produced with ranges for general industrial use.

The design was developed through a series of versions of which the Mark V was the last to be marketed although there were plans for a Mark 6 and a more advanced S & T multimeter, possibly these were the same design.

Customers may have found the weight of the original to be a problem and this was reduced by using first a deep drawn aluminium case and finally the Bakelite moulding of the Mark V. Unfortunately, the Bakelite case was inadequate for the service conditions of most of these meters, making the "Heavy Duty" designation questionable. It is quite rare to find a Mark V HD with the case intact despite the meters normally being supplied with a leather "Ever Ready" pattern case.

The production numbers were not large as far as I can judge but a Veroboard panel was certainly not normal. I would think it is very likely that this was a repair by a former user.

Replacement rear cases are extremely scarce but they are the same size as the Model 12 (Autoelectrical Meter) case and I have been told that they are interchangeable. (That does not make finding them any easier). I would also very much like to acquire one or two rear cases for these meters.

PMM

[threeseven]

Many thanks both, very interesting! Unless I'd had them side by side I would never have guessed the the Model 12 had the same lower case! I just compared my 12 with the HD V and they do indeed have the same lower! Which revealed another anomaly, the 12 has a nice aluminium instruction panel on the lower case but my example of the V has a nasty paper sheet glued on! I wonder if the original was lost somehow and a photocopy substituted? Which would be strange because as I mentioned, it is in otherwise as new condition. The vero panel is definitely OEM, it's of the non copper track type, just being used to support the resistors which are hard wired. This isn't the first time I've seen Vero used in production equipment.
I agree about the HD designation being inappropriate to this version, exemplified by mine being damaged in the post! Now the origin has been mentioned though, I think I have seen the alloy case version, which would indeed justify the HD label.

[Paul Adams]

I have recently acquired one of the these with the 'die cast case'

The serial in the appropriate section.



Threeseven, I have sent you a PM regarding your cracked case.

Paul.

[threeseven]

That does deserve the term heavy duty! Layout and construction of mine are similar but that bottom resistor area is a vero panel with blue close tolerance resistors.

[gezza123]

Hi Guys.Thanks for pictures paul,
If the mods need to move this post please do sorry.

I was just looking at pauls meter post and and seen the coils in the picture so thought they may be of use.

I found these in the junk box they may be usefull, I dont know what model they are off, but they look like the ones in pauls meter, and as I dont know anything about Avo meters they are of no use to me.

So if anyone wants them FOC for the price of the postage.
If there is a few people wanting them I will put them in a hat.

Values! there are 7 coils in all.
1x60k + 1x50k + 1x1.5k + 1x360 ohm + 1x2.2 ohm + 1x1 ohm.
One is o/c so may be used as a bobbin or rewind.
Gezza123