Glue for AVO Multimeter Glass - UK Vintage Radio Repair and Restoration Discussion Forum

hysteresis · 10th Mar 2007, 5:46 pm

I have a couple of Model 8 Mk4 AVO's (1970 and 1971) in need of restoration.

The glass from both meters is detached/partly detached. Can anybody tell me, please, what type of glass adhesive AVO would have used on these meters (I'd like to keep the restoration as authentic as possible) and if it is still available?

If not, then any advice on the suitability of a modern alternative would be most appreciated.

John

pmmunro · 10th Mar 2007, 8:47 pm

The glass in all post-war Avometers up to the Model 8 Mark V was held in place by a black compound which I cannot identify but the service manuals list ' "Bostick" (sic)Glazing Compound' as one of the recommended materials to have for repairs.

As far as I can determine, Evode Ltd, who now own the Bostik name, no longer offer a glazing compound. http://www.evode.co.uk.

The Avo manual also recommends the repairer to have 'a stick of Chatterton's compound' which I believe is described as a compound derived from gutta percha and Stockholm tar. This I imagine is no longer readily available although possible someone sufficiently determined could mix their own. From the description, I would expect this to be black, and I do not know of any other use for the Chatterton's compound if it is not used to fix the glass, or even if it would have been suitable.

As loose glasses are very common in older Avometers, I decided to compromise on authenticity and historical accuracy on this point on the grounds that the original adhesive was not entirely successful.

I have used specialist two-part glass epoxy resins with good results.

If you are interested in restoring Avometers with historic accuracy, possibly you have some others and, if so, I would be interested to know which materials have given you trouble and what solutions you have found.

The sourcing of two materials which I have yet to solve are varnished cotton sleeving and the synthetic resin bonded paper or fabric which is used to insulate the metal cases of some meters.

For the sleeving, the nearest I can find is a black varnished woven fabric which looks very similar to that used in meters of the 1940s period, but is more heat resistant than the original cotton. The natural coloured varnished cotton remains a problem.

Peter M. Munro

Skywave · 11th Mar 2007, 4:42 pm

Quote:

Originally Posted by pmmunro

The glass in all post-war Avometers up to the Model 8 Mark V was held in place by a black compound which I cannot identify but the service manuals list ' "Bostick" (sic)Glazing Compound' as one of the recommended materials to have for repairs.
Peter M. Munro

By coincidence, it just so happens that I am in the process of restoring a couple of AVO model 7s. Inside the case there is a large metal cased 1uF capacitor which had a thin paxolin sheet glued to the meter case side of it: it had come un-glued. Now I'm not altogether sure just what the adhesive was, but it looked very much like Bostik "C" adhesive to me (since I have a couple on tins in the workshop). Bostik "C" looks and has the consistency that is very similar to the stuff that is often now used to do repairs on roof felt - a sort of thick, black bitumous type of substance.
Perhaps this is what AVO were referring to.

Just a thought.

Al / Skywave.

igranic · 11th Mar 2007, 9:53 pm

Windscreen Bonding Sealant, available for about £7 for a 300ml tube via ebay and online resellers may be the answer. This is usually a self-curing, black, semi-flexible substance not dissimlar in appearance to the original meter glass adhesive or Bostik C.

radiohm · 11th Mar 2007, 10:21 pm

Could always try this roof and gutter sealant, should be widely available at D.I.Y. stores.
Will keep the original black look.

Regards.

Mike.

Station X · 11th Mar 2007, 10:45 pm

I used black silicone sealant to refix the glass in a Sifam Meter. The excess which is squeezed out can be trimmed off with a sharp blade.

It did an excellent job, but unfortunately I then managed to smash the meter bezel and glass.

Mike Phelan · 12th Mar 2007, 9:10 am

I would think it is better to use something that does not become hard. Silicon sealer or windscreen stuff sounds good.

I remember Chatterton's compound - looked like sticks of dynamite and you melted it like sealing wax. It was used to seal cable ends.

newlite4 · 12th Mar 2007, 10:35 am

I frequently encounter this problem with AVOs at work, although less so nowadays since we have moved into the digital age.
It appears that the original compound dries out and loses its tenacity.
What I have always done is to remove all of the old compound, clean with solvent and then apply Araldite Rapid (this remains slightly flexible when set).
Use a cocktail stick to apply the Araldite mix around the edge of the glass within the case, it will then find its own level.
I always thought that the Cattertons compound was used to seal the tamperproof screw into position. The manual goes into very little detail as to what these service items are actually for. Anyone know what the ball of pith is used for?
Neil

pmmunro · 12th Mar 2007, 1:46 pm

I believe that it is used to clean the moving coil pivots.

There are some people interested in clock restoration on this forum and they may be able to confirm this.

PMM.

Mike Phelan · 12th Mar 2007, 6:28 pm

Peter
(Elder) pith is used to clean pivots and tools, especially oilers, by us clock nuts. Available from the usual suspects.

10th Mar 2007, 5:46 pm	#1
hysteresis Tetrode Join Date: Feb 2007 Location: Liverpool, Merseyside, UK. Posts: 99	Glue for AVO Multimeter Glass I have a couple of Model 8 Mk4 AVO's (1970 and 1971) in need of restoration. The glass from both meters is detached/partly detached. Can anybody tell me, please, what type of glass adhesive AVO would have used on these meters (I'd like to keep the restoration as authentic as possible) and if it is still available? If not, then any advice on the suitability of a modern alternative would be most appreciated. John

10th Mar 2007, 8:47 pm	#2
pmmunro Octode Join Date: Jul 2004 Location: Dundee, UK. Posts: 1,813	Re: Glue for AVO Multimeter Glass The glass in all post-war Avometers up to the Model 8 Mark V was held in place by a black compound which I cannot identify but the service manuals list ' "Bostick" (sic)Glazing Compound' as one of the recommended materials to have for repairs. As far as I can determine, Evode Ltd, who now own the Bostik name, no longer offer a glazing compound. http://www.evode.co.uk. The Avo manual also recommends the repairer to have 'a stick of Chatterton's compound' which I believe is described as a compound derived from gutta percha and Stockholm tar. This I imagine is no longer readily available although possible someone sufficiently determined could mix their own. From the description, I would expect this to be black, and I do not know of any other use for the Chatterton's compound if it is not used to fix the glass, or even if it would have been suitable. As loose glasses are very common in older Avometers, I decided to compromise on authenticity and historical accuracy on this point on the grounds that the original adhesive was not entirely successful. I have used specialist two-part glass epoxy resins with good results. If you are interested in restoring Avometers with historic accuracy, possibly you have some others and, if so, I would be interested to know which materials have given you trouble and what solutions you have found. The sourcing of two materials which I have yet to solve are varnished cotton sleeving and the synthetic resin bonded paper or fabric which is used to insulate the metal cases of some meters. For the sleeving, the nearest I can find is a black varnished woven fabric which looks very similar to that used in meters of the 1940s period, but is more heat resistant than the original cotton. The natural coloured varnished cotton remains a problem. Peter M. Munro

11th Mar 2007, 9:53 pm	#4
igranic Rest in Peace Join Date: Jan 2005 Location: North Bedfordshire, UK. Posts: 395	Re: Glue for AVO Multimeter Glass Windscreen Bonding Sealant, available for about £7 for a 300ml tube via ebay and online resellers may be the answer. This is usually a self-curing, black, semi-flexible substance not dissimlar in appearance to the original meter glass adhesive or Bostik C.

11th Mar 2007, 10:21 pm	#5
radiohm Pentode Join Date: Jan 2006 Location: Stockton On Tees, Cleveland Posts: 18	Re: Glue for AVO Multimeter Glass Could always try this roof and gutter sealant, should be widely available at D.I.Y. stores. Will keep the original black look. Regards. Mike. Attached Thumbnails

11th Mar 2007, 10:45 pm	#6
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Glue for AVO Multimeter Glass I used black silicone sealant to refix the glass in a Sifam Meter. The excess which is squeezed out can be trimmed off with a sharp blade. It did an excellent job, but unfortunately I then managed to smash the meter bezel and glass. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

12th Mar 2007, 9:10 am	#7
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Glue for AVO Multimeter Glass I would think it is better to use something that does not become hard. Silicon sealer or windscreen stuff sounds good. I remember Chatterton's compound - looked like sticks of dynamite and you melted it like sealing wax. It was used to seal cable ends. __________________ Mike.

12th Mar 2007, 10:35 am	#8
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	Re: Glue for AVO Multimeter Glass I frequently encounter this problem with AVOs at work, although less so nowadays since we have moved into the digital age. It appears that the original compound dries out and loses its tenacity. What I have always done is to remove all of the old compound, clean with solvent and then apply Araldite Rapid (this remains slightly flexible when set). Use a cocktail stick to apply the Araldite mix around the edge of the glass within the case, it will then find its own level. I always thought that the Cattertons compound was used to seal the tamperproof screw into position. The manual goes into very little detail as to what these service items are actually for. Anyone know what the ball of pith is used for? Neil

12th Mar 2007, 1:46 pm	#9
pmmunro Octode Join Date: Jul 2004 Location: Dundee, UK. Posts: 1,813	Re: Glue for AVO Multimeter Glass I believe that it is used to clean the moving coil pivots. There are some people interested in clock restoration on this forum and they may be able to confirm this. PMM.

12th Mar 2007, 6:28 pm	#10
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Glue for AVO Multimeter Glass Peter (Elder) pith is used to clean pivots and tools, especially oilers, by us clock nuts. Available from the usual suspects. __________________ Mike.