AVO Model 9 Mk 2 - UK Vintage Radio Repair and Restoration Discussion Forum

TonyDuell · 19th Jan 2017, 4:57 pm

I assume that's 'vintage'.

I bought an AVO meter Model 9 Mk2 this morning at an antique fair of all places. I found the user manual on the web, at least it includes the circuit diagram and parts lists. Annoyingly it tells me that a 'service manual is available', but I guess niot any more.

I've not tested it much yet, so far I've only noticed :

Paint spilt on the casing.

Handle missing. I assume this is just a leather strap. Has anyone ever made one (or is it a case of 'cut up a trouser belt'

)

15V battery missing

1.5V cell almost flat.

The good news : The meter movement seems fine. On the 3V DC range a pair of fresh D cells in series take the pointer past the RH end stop and it is very smooth with no tendency to stick.

Am I right in thinking that the Model 9 is very similar to the Model 8 (just with different ranges) and is quite a useable meter?

Refugee · 19th Jan 2017, 5:35 pm

I have two 9s.
I made 15 volt batteries with 5 lithium coin cells and a 15mm water pipe stop end as a spacer to make up the length. A few turns of insulation tape holds the cells in line.

Hartley118 · 19th Jan 2017, 6:20 pm

AFAIR, the AVO Model 9 is much like the Model 8 but with international symbols for voltage and current instead of plain English.

Martin

The Philpott · 19th Jan 2017, 11:50 pm

Yes very similar to model 8 but scale is a 30/100 type instead of the 25/100 type found on the model 8. This arrangement goes all the way up to the HT range which is 3000v max in place of 2500v.

The best place to get a replacement leather strap cut to length may well be a place that does horse tack. I sketched a template on the shed wall which i can measure if you want to get the right length and get the holes/slits in the right place.

Bakelite seems immune to wd40 so that may be a help in getting old paint off. It does get scratched very easily however if sharp tools are used

The Philpott · 20th Jan 2017, 11:50 am

See attached thumbnails of leather strap outline. The inner lines were cosmetic on the strap i used for this template, merely pressed into the leather. The details differs a little from unit to unit (and some would have been made ad-hoc) so if you make one yourself you can't be accused of being 'wrong'

overall length- 293mm
length between hole c/lines- 255.5mm
width- 26mm
hole diam- 4 - 4.5mm?
length of slit- 10 - 11mm?
strap thickness - 3 - 3.3mm?

The question marks are because every example is already rather worn and it's difficult to be exact with those dimensions. If you get an overlength horsey strap you can practice a bit!

Where no strap is immediately available i have used lightweight zinc plated chain from the ironmongers- crimped in at either end with mole grips to ensure it doesn't slip off. It can be carefully removed later on with the same mole grips- just crimp at right angles to the original crimp. Somewhat unsafe with high voltage or current and inadvisable with the battery box open but an avometer without any sort of strap WILL get dropped sooner rather than later, hence this emergency measure. (no photo available but can provide if required)

....Don't be tempted to use a strap from a donor meter until it has had leather food massaged into the ends and left for a couple of days. The clearances are quite tight where they slip onto the nickel plated ferrules and it is very easy to chip a lump out of the leather as each end is removed.

There is a broken meter on ebay currently that has only got up to £3 bid; can't see the strap from the photo.

Dave

Nicklyons2 · 20th Jan 2017, 5:15 pm

I've found a useful tool for scratching off paint from plastics/delicate surfaces - old bank & credit cards. The edges are nearly as good as using your thumb nail and they are soft enough not to cause any noticeable damage - don't go mad though!

For softening, it really depends on the paint: I've been pleasantly surprised once or twice that warm water & washing up liquid softens some; others meths or white spirit. I use a cotton bud soaked in the preferred solvent and rub it on a section of the paint and see what happens first.

TonyDuell · 20th Jan 2017, 10:08 pm

Thanks for the tip of going to a country/riding shop for a strap. I live sufficiently far out of London that there are such places near me, so I will give them a go. I have a Model 8 that I can look at the strap on to get some idea (I won't try to remove it though).

As for the paint, my experience is that Bakelite is not attacked by common chemicals. I will try water/detergent, meths, white spirit, etc.

19th Jan 2017, 4:57 pm	#1
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,218	AVO Model 9 Mk 2 I assume that's 'vintage'. I bought an AVO meter Model 9 Mk2 this morning at an antique fair of all places. I found the user manual on the web, at least it includes the circuit diagram and parts lists. Annoyingly it tells me that a 'service manual is available', but I guess niot any more. I've not tested it much yet, so far I've only noticed : Paint spilt on the casing. Handle missing. I assume this is just a leather strap. Has anyone ever made one (or is it a case of 'cut up a trouser belt' ) 15V battery missing 1.5V cell almost flat. The good news : The meter movement seems fine. On the 3V DC range a pair of fresh D cells in series take the pointer past the RH end stop and it is very smooth with no tendency to stick. Am I right in thinking that the Model 9 is very similar to the Model 8 (just with different ranges) and is quite a useable meter?

19th Jan 2017, 5:35 pm	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: AVO Model 9 Mk 2 I have two 9s. I made 15 volt batteries with 5 lithium coin cells and a 15mm water pipe stop end as a spacer to make up the length. A few turns of insulation tape holds the cells in line. Attached Thumbnails

19th Jan 2017, 6:20 pm	#3
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: AVO Model 9 Mk 2 AFAIR, the AVO Model 9 is much like the Model 8 but with international symbols for voltage and current instead of plain English. Martin __________________ BVWS Member

19th Jan 2017, 11:50 pm	#4
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,108	Re: AVO Model 9 Mk 2 Yes very similar to model 8 but scale is a 30/100 type instead of the 25/100 type found on the model 8. This arrangement goes all the way up to the HT range which is 3000v max in place of 2500v. The best place to get a replacement leather strap cut to length may well be a place that does horse tack. I sketched a template on the shed wall which i can measure if you want to get the right length and get the holes/slits in the right place. Bakelite seems immune to wd40 so that may be a help in getting old paint off. It does get scratched very easily however if sharp tools are used

20th Jan 2017, 11:50 am	#5
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,108	Re: AVO Model 9 Mk 2 See attached thumbnails of leather strap outline. The inner lines were cosmetic on the strap i used for this template, merely pressed into the leather. The details differs a little from unit to unit (and some would have been made ad-hoc) so if you make one yourself you can't be accused of being 'wrong' overall length- 293mm length between hole c/lines- 255.5mm width- 26mm hole diam- 4 - 4.5mm? length of slit- 10 - 11mm? strap thickness - 3 - 3.3mm? The question marks are because every example is already rather worn and it's difficult to be exact with those dimensions. If you get an overlength horsey strap you can practice a bit! Where no strap is immediately available i have used lightweight zinc plated chain from the ironmongers- crimped in at either end with mole grips to ensure it doesn't slip off. It can be carefully removed later on with the same mole grips- just crimp at right angles to the original crimp. Somewhat unsafe with high voltage or current and inadvisable with the battery box open but an avometer without any sort of strap WILL get dropped sooner rather than later, hence this emergency measure. (no photo available but can provide if required) ....Don't be tempted to use a strap from a donor meter until it has had leather food massaged into the ends and left for a couple of days. The clearances are quite tight where they slip onto the nickel plated ferrules and it is very easy to chip a lump out of the leather as each end is removed. There is a broken meter on ebay currently that has only got up to £3 bid; can't see the strap from the photo. Dave Attached Thumbnails

20th Jan 2017, 5:15 pm	#6
Nicklyons2 Octode Join Date: Jan 2013 Location: Barnsley, South Yorkshire, UK. Posts: 1,517	Re: AVO Model 9 Mk 2 I've found a useful tool for scratching off paint from plastics/delicate surfaces - old bank & credit cards. The edges are nearly as good as using your thumb nail and they are soft enough not to cause any noticeable damage - don't go mad though! For softening, it really depends on the paint: I've been pleasantly surprised once or twice that warm water & washing up liquid softens some; others meths or white spirit. I use a cotton bud soaked in the preferred solvent and rub it on a section of the paint and see what happens first.

20th Jan 2017, 10:08 pm	#7
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,218	Re: AVO Model 9 Mk 2 Thanks for the tip of going to a country/riding shop for a strap. I live sufficiently far out of London that there are such places near me, so I will give them a go. I have a Model 8 that I can look at the strap on to get some idea (I won't try to remove it though). As for the paint, my experience is that Bakelite is not attacked by common chemicals. I will try water/detergent, meths, white spirit, etc.