Advice on repairing AVO Front.

[Paul Adams]

People with a sensitive disposition should look away now.

I recently acquired this AVO 8 MkII, unfortunately it has not been very well looked after by a previous owner, as the photo’s show.

Has anyone had any successful experience in repairing bakelite with modern adhesives, and what adhesive would one recommend?

Any suggestions appreciated.

Paul.

[Leon Crampin]

I would suggest slow-set Araldite, but applied very sparingly and warmed to make it less viscous. The phenolic parts should also be well warmed, so any sensitive components such as the movement and the bridge rectifier should be removed first.

Have a pre-arranged means of pre-loading the joint, and allow the adhesive to set in a warm location. The idea is that warming lowers the viscosity of the resin allowing it to penetrate the porous surface of the phenolic. A very strong bond will result if you achieve this.

Put your "spare" adhesive in the same warm place as the workpiece, and test periodically with a knife to see when it can be pared away cleanly. Take a sharp knife and clean up the exuding adhesive on the front and edges of the panel. If you get your timing right, you can make the joint almost invisible and the surplus adhesive will just peel away like a rubbery string.

I wish your AVO a speedy recovery - I've had a few in intensive care, but never to this extent...

Leon.

[Refugee]

What a nasty accident.
Resin can be bought from a boat builders. They also sell coloring stuff to add in order to get a match with the original case. The colors should also work with car body filler. It will need to be put together dry first so that a sequence can be worked out before using the resin to fit it all back otherwise you may get bits that will not go back in. It will have to be done in several sittings by the looks.
There will almost certainly be little bits missing and i am not sure if the dyes will work with Araldite without doing an experiment.

[Freya]

the JB Kwik weld is good too as its almost the same colour, i tried some on a test piece of broken bakelite and ended up snapping in another place.

I was too going to suggest slow set (called precision now) araldite, Leons advice is good.

[Paul Adams]

Repair completed, not entirely invisible but better than it was to start with.

I settled for this stuff (http://uk.rs-online.com/web/p/repair...sives/0850962/) which we used to use at work, black in colour a metal loaded epoxy.
(I just happened to have a bit lying around )

Amazingly the meter still works, it must have had a real whack.

Thanks to everyone who replied.

Paul.

[Radio Wrangler]

I don't think you want metal-loaded epoxy for fixing an AVO case. Something with good insulating properties is called for. All the stuff inside that case can float at quite unpleasant voltages, depending on what and how you're probing.

David

[David Simpson]

Paul, the advice regarding using araldite would be best, plus the warming process. No one has mentioned cleaning the surfaces to be joined - I used celuloise thinners on a rare 8 Mk1, similarly broken, some time ago. Very sparingly & in a well ventilated area I must add.
I also carefully cut out a small unimportant piece of the battery box and filed it down - then mixed the filings with more araldite after the initial joining - to fill in any wee recesses in the join.
When applying the araldite to the initial join - dont spread it out to the outer edge. It'll squeeze itself when everything is in place. Wiping or scraping as it sets only makes a mess.
Small joinery or furniture clamps are ideal for keeping the re-made break aligned while it sets. Twisted thin copper wire for the awkward angles.
Nothing coarser than P600 abrasive paper for the first rub-down, P1500 gives a final smooth. Then a final polish with Farecla G6 compound.
Good on yer for saving a lovely old AVO.

Regards, David

[Phil G4SPZ]

Well done Paul. I've never seen an Avo with a broken front panel before. Your repair may not be entirely invisible, but my grandmother, who was a needlewoman, used to have a nice expression - "better an imperfect repair than a perfect hole".

Avometers are pieces of industrial equipment that probably never looked pristine once out of the box. Yours is lucky to survive, so its visible scars are a small price to pay.