AVO Electronic Test Meter - getting the case off. - UK Vintage Radio Repair and Restoration Discussion Forum

Nanozeugma · 29th Oct 2020, 1:38 pm

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?

barrymagrec · 29th Oct 2020, 1:42 pm

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.

Silicon · 29th Oct 2020, 2:59 pm

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.

Craig Sawyers · 29th Oct 2020, 4:50 pm

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

merlinmaxwell · 29th Oct 2020, 4:57 pm

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.

The Philpott · 29th Oct 2020, 6:04 pm

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

Dekatron · 1st Nov 2020, 12:18 pm

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.

Silicon · 1st Nov 2020, 12:27 pm

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

29th Oct 2020, 1:38 pm	#1
Nanozeugma Hexode Join Date: Nov 2017 Location: London, UK. Manchester once a month :) Posts: 422	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? Attached Thumbnails __________________ Thermionic Emission, cures depression, boredom and piles.

29th Oct 2020, 1:42 pm	#2
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,014	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.

29th Oct 2020, 2:59 pm	#3
Silicon Octode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 1,320	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.

29th Oct 2020, 4:50 pm	#4
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 3,020	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

29th Oct 2020, 4:57 pm	#5
merlinmaxwell Dekatron Join Date: Jul 2008 Location: Maidenhead, Berkshire, UK. Posts: 10,286	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. __________________ Cats have staff, it's dogs that have owners.

29th Oct 2020, 6:04 pm	#6
The Philpott Nonode Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 2,525	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

1st Nov 2020, 12:18 pm	#7
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,181	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. __________________ Martin, Sweden

1st Nov 2020, 12:27 pm	#8
Silicon Octode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 1,320	Re: AVO Electronic Test Meter - getting the case off. Polygrip pliers are known as slip joint water pump pliers in the UK.