AVO Electronic Test Meter - getting the case off.
 

Hi.
Trying to restore one of these and hit a snag...

In order to get the upper half of the case off, you need to remove the knobs - obviously.
But then you find out how they have been attached.
Grubscrew? D clip? Collect? No. no and no.
I've never seen this arrangement before, anyone else?

The dowel / split pin is steel and it isn't shifting.
I'm nervous about getting agricultural with it and applying to much percussive maintenenace..... One might be forgiven thinking AVO didn't want you to take the cover off...

Any ideas?

Re: AVO Electronic Test Meter - getting the case off.
 

Put a suitable size nut or other spacer over one end of the pin and use a large pair of pliers to squeeze the pin out.

Re: AVO Electronic Test Meter - getting the case off.
 

I would improvise some form of 'puller' to slowly push the pin out and then re-insert it after the restoration is complete.

I am always nervous about the potential damage from 'shock waves' when hammers are used.

Re: AVO Electronic Test Meter - getting the case off.
 

That is the classic AVO knob. Fitted to the Mk3, Mk4, CT160 valve testers, and the transistor testers too. And also - as you have just found - the Electronic Testmeter.

I have got the pins out when needed by using a pair of pliers to push the pin flush with one side of the shaft. Then grab the long end in the same pair of pliers and pull. Or alternatively at that stage a suitable diameter punch (or drill bit) and tap it out the remaining way.

Remember that AVO fitted those pins after assembly in the first place!

Craig

Re: AVO Electronic Test Meter - getting the case off.
 

Known as roll pins, put a bit of oil on the ingoing bit before squeezing to aid removal. Sometimes pushing the other way (again with oil on it) frees it up a bit more. Best to use new ones when replacing.

Re: AVO Electronic Test Meter - getting the case off.
 

If the roll pin size is 'correct' for the hole it occupies, it may be possible to compress both ends with small self-grip wrenches to defeat it's seizure.. ie closing the roll pin to a marginally smaller diam.

IF (repeat if!) it's feasible to use some heat, wd40 can be applied afterwards, as the cooling joint draws the lubricant in to where it's needed.

Dave

Re: AVO Electronic Test Meter - getting the case off.
 

On early models AVO used different size on the hole in the collar, the side with the beveled hole is usually the larger hole (only by some tenths of a millimeter) and it is easier to push the pin out from the other end then (the side with the smaller hole) - later models have equal sized holes.

You can use a polygrip plier to compress and also to rotate the pin if it has seized up.

I usually put a tube, some 10-15 mm long, that fit on the pin on the side that I want it to be pushed out at and then use the polygrip plier on this tube and the pin to push it out into the tube far enough so that I can grip it and pull it out while rotating it slightly.

Re: AVO Electronic Test Meter - getting the case off.
 

Polygrip pliers are known as slip joint water pump pliers in the UK.