Replacement of AVO 8 meter window

[Billy T]

Greetings from Auckland. New Zealand.

New member/first post! I am restoring an old AVO 8 with a cracked meter window. I assume that replacements are no longer available so I plan to replace it with one cut from clear acrylic however the original is glued in and I'd like to know how best to remove it. The movement has been removed per the service manual instructions but I can't see how I can get the cracked remains out short of breaking it into small pieces. Is there a recommended method such as heat/solvent etc?

This meter has sentimental value as it was given to me from the estate of an old friend (ex UK) and I'd like to get it back into usable order if I can.

Cheers

Billy

[Billy T]

Sorry to bring this thread forward again, but I am still looking for ideas on how to remove the broken meter glass. These glasses are easily broken (this one by dropping a screwdriver) so surely somebody out there must have attempted a repair? I don't want to use too much force or "impact" methods in case I damage the bakelite housing.

Cheers

Billy

[newlite4]

Billy, just drizzle some lighter fluid around the edges of the glass, this will soften the bonding compound within a few minutes. Use the same stuff to clean-off the remainder of the compound from the recess.
Neil

[Tim]

I would recommend the use of real glass for this job. I replaced a meter glass with plastic once and the meter needle stuck to it if the plastic was touched(static?).
The thin glass used should be obtainable from picture frames/restorers.

Thanks for the tip re. lighter fluid, Neil

[audiomm]

Originally Posted by Billy T

Greetings from Auckland. New Zealand.

New member/first post! I am restoring an old AVO 8 with a cracked meter window. I assume that replacements are no longer available so I plan to replace it with one cut from clear acrylic however the original is glued in and I'd like to know how best to remove it. The movement has been removed per the service manual instructions but I can't see how I can get the cracked remains out short of breaking it into small pieces. Is there a recommended method such as heat/solvent etc?

This meter has sentimental value as it was given to me from the estate of an old friend (ex UK) and I'd like to get it back into usable order if I can.

Cheers

Billy

I've done this a few times. Try using one of those disposable/snap off blades to slice around the perimeter between the case body & the glass. Try not to break the glass any further as you probably have just the two pieces at the moment. Once removed, tape the bits together & take it to your local glass merchant and get them to cut an exact copy. Last one I got cut was $5. Refitting is the easy bit - I used Ados F2 contact adhesive as the glue - not exactly original but it works.

[Billy T]

Thanks for the advice guys, especially about the glass, it is beginning to sound a lot easier than I thought it would be!

Now for the idiotic question: What is the chemical composition of lighter fluid? Is it a light hydrocarbon or similar? I ask because smoking is a fast dying habit here in NZ (pardon the pun) and nobody uses refillable lighters any more, they mostly use the disposable gas type or occasionally matches, so finding lighter fluid will be a mission.

I have a large range of solvents though, so maybe I'll select the one that seems most likely and try that. I have a paintbrush cleaner in mind that I use for all sorts of cleaning/dissolving projects and there is very little that it won't touch.

Cheers

Billy

[newlite4]

Billy, lighter fluid is just petrol in a purified form or Diethyl Ether. It should be easy to obtain "Zippo" lighter fluid from any hardware store, any chemist should be able to supply "Pet Ether".
Neil

[Brian R Pateman]

The great advantage with lighter fluid is that is has no additives and evaporates very quickly leaving no residue.

I always have a tin handy.

Regards,

[Mike Phelan]

Billy
IPA (isopropyl alcohol, not India pale ale!) is similar, evaporates completely and is miscible with water; I use it for clock cleaning and other things; quite cheap from CPC here, don't know about in the Antipodes; Andrew (arjoll) will probably know.

[Brian R Pateman]

In the course of a little gentle archiving I found this thread:-

https://www.vintage-radio.net/forum/...ad.php?t=15340

which you might find useful.

(I knew I'd seen it somewhere!)

Regards,

[Billy T]

Originally Posted by Mike Phelan

Billy
IPA (isopropyl alcohol, not India pale ale!) is similar, evaporates completely and is miscible with water; I use it for clock cleaning and other things; quite cheap from CPC here, don't know about in the Antipodes.

Isopropyl alcohol is readily available, and I have plenty here, but it sounds like lighter fluid would be better and I might find some if I go to a smoker's shop, there's probably one left somewhere. Until a few months back we had a genuine old-style Barber's shop in our local shopping centre, complete with all the faded junk in the window, stale cigars and bottles of lighter fluid. Now it looks like a knocking shop and haircuts cost double their previous price. Should've bought some lighter fluid before the change.

Thanks to all for the sound advice,

Cheers

Billy

[Billy T]

Recapping, I am restoring an old AVO 8 with a cracked meter window. The original isglued in and I'd like to know how best to remove it. The movement has been removed per the service manual instructions but I can't see how I can get the cracked remains out, short of breaking it into small pieces. This meter has sentimental value as it was given to me from the estate of an old friend (ex UK).

The removal advice received was as follows:

"Just drizzle some lighter fluid around the edges of the glass, this will soften the bonding compound within a few minutes. Use the same stuff to clean-off the remainder of the compound from the recess".

I finally found some Zippo lighter fluid and have soaked around the glass for many hours, renewing the fluid at regular intervals as it evaporates. I am applying it from the inside as there is a well around much of the glass that will hold liquid. So far there is not the slightest sign that the fluid is getting into the bonding compound and I am reluctant to apply pressure because I need to keep the old glass as a template.

Further ideas or advice would be appreciated. Should I turn it over and drown it from the top, or would heating with a hairdryer help?

Cheers

Billy

[pmmunro]

Billy,

I would try some gentle heating as this softens most adhesives. You will have to be sure that all the lighter fluid has evaporated to eliminate any fire risk and I'm sureyou don't have to be told that theBakelite should not be overheated.

PMM.

[Leon Crampin]

I'm pretty sure the glass on the "proper" AVOs was stuck in using Black Bostik adhesive. This is no longer available as far as I know, but I do recall Bostik sold a solvent for it.

Very regrettably this solvent was benzine. As this substance has now been identified as being carcinogenic, I could not propose its use.

It did occur to me that the foam pads in the battery box are stuck on with the same adhesive. It might be possible to scrape a little from this location and experiment with various solvents. I would try acetone for starters.

The adhesive holding the glass will be very well hardened to the point where it will be difficult to get any likely solvent to act on it before it evaporates. With the front panel in its working (horizontal) position, you could try filling the glass recess with solvent, then taping over the top to prevent evaporation - movement removed of course.

Leon.

[SeanMcK]

Would it not be possible to take a rubbing of the glass or at least its edges? That way you have a pattern at least.
The service manual for the MkI & II lists "Bostick glazing compound" under miscellaneous item which I'd guess is the black stuff.
If solvents dont work what about an old style razor blade and some patient scraping/cutting

[Billy T]

I see the Mods have married together my new thread from last night and my original posting from some time back. Thanks for that, it keeps the discussion all in one place for future reference.

Further close examination in the bright morning light revealed some of the original adhesive smeared outside the edge of the glass, so I was able to check on that and it is definitely not responding to Zippo.

Fortunately I have a very wide range of common and exotic solvents here left over from previous work (testing electronic evidential breath test machines, which is a sideline area of expertise for me) so I will try them all with cotton wool buds and see if any will dissolve the accessible adhesive. It looks absolutely original so I don't think there's any chance I'm up against epoxy or any other "permanent" fixative.

Speed of evaporation is a big problem, the Zippo is gone in minutes, not hours, so I might try putting it the meter in my workshop fridge to slow things down a little.

Thank you all for the ongoing assistance and advice.

Cheers

Billy

[Billy T]

Great rejoicing!!

I finally found a viable solvent and was able to remove the broken glass without further damage.

I tried Toluene, Methanol, Xylol, Trichloroethane, Methyl-Ethyl-Ketone (MEK), Lacquer thinners, Acetone, Acetone-free nail polish remover, standard nail polish remover, Isopropyl Alcohol plus other alcohol variations, and of course, Zippo Lighter Fluid.

The only substances that would touch it at all were MEK (too dangerous to breath) Acetone-free NP remover (left greasy residues) and pure Acetone.

I settled on pure Acetone and after several soaks last night plus a concentrated attack this morning from both sides of the glass it finally came free. The adhesive is a black rubbery compound that did not dissolve, it just softened and returned very quickly to its original state as the solvent evaporated.

The meter serial number is 10.037.667 (looks like an IP address!) and I would be very grateful if anybody can tell me the age and series. As mentioned previously, it came from the estate of a dear friend who emigrated from the UK back in the '50s I think and was a very prominent member of the industry here here in NZ, and was given to me by his daughter, so I am keen to know a little more about it.

Incidentally, it appears that the glass was hand-cut because it is anything but symmetrical and no two opposing dimensions are the same.

Thanks for all the advice and help.

Cheers

Billy

[Billy T]

The meter serial number is 10.037.667 ( and I would be very grateful if anybody can tell me the age and series.

In my enthusiasm and haste to post the good news and solvent used, I clean forgot that I already knew the model , it is a Series 9 MKII so it is just the approximate age I wish to determine thanks.

Cheers

Billy

[russell_w_b]

Originally Posted by Billy T

In my enthusiasm and haste to post the good news and solvent used, I clean forgot that I already knew the model , it is a Series 9 MKII so it is just the approximate age I wish to determine thanks.

Cheers

Billy

June 1967. Look at the last three digits (may be four). The last two refer to the year (67 = 1967). The first one - or two - the month (6 = June).

You'll need a more experienced Avorak to tell you about the other numbers!

[Mike-repairman]

Methyl-Ethyl-Ketone brings back memories. Believe it or not we used to used this in the composing room at the printers I worked at in the 60's for cleaning copper printing plates.
It used to make you feel a bit light-headed. Then all of a sudden it was banned outright overnight. A print worker in another part of the country had died of the fumes! Horrid stuff as we know now, but I guess a lot of the other solvents were nearly as bad.

Mike.