Avo 8??? - UK Vintage Radio Repair and Restoration Discussion Forum

avocollector · 25th May 2019, 3:44 pm

Bought this off the local NZ internet auction site trademe. Not seen one quite like it before as it has no divide by 2 button just a reverse MC one and a divide by 100 ohms position as well as a LR switch position (Low Resistance). On the back the instructions seem to say it's a 8 mk 3 but both the front and the meter say only 8.

Don't know how rare these models are but if anybody has any info that would be great. Some pics below.

The Philpott · 25th May 2019, 5:07 pm

Excellent! i think that is indeed a fairly early Mk.III Model 8. They were up to serial number 79,000 by year 1968 so 2,400 is an early bird. The little '8 ball' button on the front facia has been seen before, but not very often. Perhaps it is a feature that was phased out as time went on.

There will be probably be more windings inside than you would find on a later Mk III, component resistors proliferated later on in the production run.

This is the swiss army knife of Avo's i suppose, but the x100 gap between the resistance ranges is a little bit of a handicap.

Dave

Paul_RK · 25th May 2019, 5:20 pm

Hmm... does not the back plate refer to the meter being a Model S MkIII?

https://www.vintage-radio.net/forum/...d.php?t=124814

Paul

pmmunro · 25th May 2019, 5:50 pm

Based on advertising, the Model 8 Mk III was introduced in June 1964, so you're right Dave, this would be an early Mk III. Possibly the "8 Mk III" buttons were not available early on but I think you're right they fell into disuse later.

Avocollector,

The Model 8 always had a REV MC (Reverse Moving Coil) push button switch. The Divide by Two facility was used on the Model 7 and Model 40 of this era and was first used in 1933 to expand the 20 ranges of the "Universal Avometer" to 34 ranges, soon afterwards becoming 36-ranges. The feature was patented (GB 423199) but the patent was successfully chalenged by Taylor Instruments. I haven't found any evidence that the feature was ever used by Taylor, not unless you count the Model 8 Mk V as a Taylor instrument since its centre pole movement was to a Taylor patent and the Mk V design was largely the responsibility of an engineer who came from Taylor when they were taken over by AVO.

PMM

Sinewave · 25th May 2019, 7:24 pm

Quote:

Originally Posted by Paul_RK

Hmm... does not the back plate refer to the meter being a Model S MkIII?

https://www.vintage-radio.net/forum/...d.php?t=124814

Paul

That's an 8 with a slightly scratched rear plate. The scratch makes the 8 look like an S at quick glance.

The Philpott · 25th May 2019, 7:50 pm

Paul-
Does look like an 'S' but it's likely just an '8' with a scratch across it! (Edit- Anthony beat me to it)

NZ Peter-
Watch that leather strap; they're (only) good for 50yrs or so.. Any held up to my ear that crackle when pinched get de-commissioned!

Dave

avocollector · 26th May 2019, 2:20 pm

Quote:

Originally Posted by Paul_RK

Hmm... does not the back plate refer to the meter being a Model S MkIII?

https://www.vintage-radio.net/forum/...d.php?t=124814

Paul

Hi - no I've looked under a 10x lens and it IS a scratch - you can see traces of the 8 on the right hand side. So it says 8 mkIII.

avocollector · 26th May 2019, 2:26 pm

Thanks to everybody for the information - not come across one of these models before and all the other earlier 8's I've got are marked 8 mkII or 8 mk III from memory on the front button. Must go and get them out and have a look!! Amazing the variants - before I started collecting these about 10 years ago there were just large black Avos in my mind and I never realised there were different models until I joined this forum.

Refugee · 26th May 2019, 2:36 pm

At college we had 7s and 8s and were told all about ohms per volt.
10 meg ohm electronic volt meters were quite special at the time but we were shown one.
I have ended up with two 9s in my workshop but at least they are the same ohms per volt as 8s and with only a small difference in the ranges get pretty close to an 8 on valve gear.

25th May 2019, 3:44 pm	#1
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 653	Avo 8??? Bought this off the local NZ internet auction site trademe. Not seen one quite like it before as it has no divide by 2 button just a reverse MC one and a divide by 100 ohms position as well as a LR switch position (Low Resistance). On the back the instructions seem to say it's a 8 mk 3 but both the front and the meter say only 8. Don't know how rare these models are but if anybody has any info that would be great. Some pics below. Attached Thumbnails

25th May 2019, 5:07 pm	#2
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,106	Re: Avo 8??? Excellent! i think that is indeed a fairly early Mk.III Model 8. They were up to serial number 79,000 by year 1968 so 2,400 is an early bird. The little '8 ball' button on the front facia has been seen before, but not very often. Perhaps it is a feature that was phased out as time went on. There will be probably be more windings inside than you would find on a later Mk III, component resistors proliferated later on in the production run. This is the swiss army knife of Avo's i suppose, but the x100 gap between the resistance ranges is a little bit of a handicap. Dave

25th May 2019, 5:20 pm	#3
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,255	Re: Avo 8??? Hmm... does not the back plate refer to the meter being a Model S MkIII? https://www.vintage-radio.net/forum/...d.php?t=124814 Paul

25th May 2019, 5:50 pm	#4
pmmunro Octode Join Date: Jul 2004 Location: Dundee, UK. Posts: 1,813	Re: Avo 8??? Based on advertising, the Model 8 Mk III was introduced in June 1964, so you're right Dave, this would be an early Mk III. Possibly the "8 Mk III" buttons were not available early on but I think you're right they fell into disuse later. Avocollector, The Model 8 always had a REV MC (Reverse Moving Coil) push button switch. The Divide by Two facility was used on the Model 7 and Model 40 of this era and was first used in 1933 to expand the 20 ranges of the "Universal Avometer" to 34 ranges, soon afterwards becoming 36-ranges. The feature was patented (GB 423199) but the patent was successfully chalenged by Taylor Instruments. I haven't found any evidence that the feature was ever used by Taylor, not unless you count the Model 8 Mk V as a Taylor instrument since its centre pole movement was to a Taylor patent and the Mk V design was largely the responsibility of an engineer who came from Taylor when they were taken over by AVO. PMM

25th May 2019, 7:50 pm	#6
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,106	Re: Avo 8??? Paul- Does look like an 'S' but it's likely just an '8' with a scratch across it! (Edit- Anthony beat me to it) NZ Peter- Watch that leather strap; they're (only) good for 50yrs or so.. Any held up to my ear that crackle when pinched get de-commissioned! Dave

26th May 2019, 2:26 pm	#8
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 653	Re: Avo 8??? Thanks to everybody for the information - not come across one of these models before and all the other earlier 8's I've got are marked 8 mkII or 8 mk III from memory on the front button. Must go and get them out and have a look!! Amazing the variants - before I started collecting these about 10 years ago there were just large black Avos in my mind and I never realised there were different models until I joined this forum.

26th May 2019, 2:36 pm	#9
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Avo 8??? At college we had 7s and 8s and were told all about ohms per volt. 10 meg ohm electronic volt meters were quite special at the time but we were shown one. I have ended up with two 9s in my workshop but at least they are the same ohms per volt as 8s and with only a small difference in the ranges get pretty close to an 8 on valve gear.