AVO 2 panel valve tester stiff rotary switch - UK Vintage Radio Repair and Restoration Discussion Forum

Viewmaster · 5th Nov 2022, 5:15 pm

I have one of these AVO panel testers, but the rotary switch that selects 0 -9 on each rotary, some are rather stiff to turn. I tried a little WD 40 but with little improvement. Sprayed both inside and outside the switches.
Any ideas, please, how to ease the movement ?

Stevie342000 · 5th Nov 2022, 6:23 pm

Not sure it is advised to use WD40 anywhere near bakelite - google will tell you, google will also tell you dismantle the rollers but becareful....

Dekatron · 5th Nov 2022, 6:40 pm

There are several threads on this forum regarding this so search the forum first.

In general you shouldn't use anything to lubricate the roller selectors with, just dismantle them all and clean them thoroughly with IPA and put them back. Polishing some pieces with dry graphite powder/lubrication which you then remove again might help some pieces move more smoothly. Take care to not rub the white paint as it easily comes off. You can repaint it if you need but it is tedious work.

Any lubrication will only let dust accumulate and make it into a goo that stiffens over time.

Electronpusher0 · 6th Nov 2022, 9:44 am

WD40 should NOT be used on the AVO roller switches, the only proper way is to fully dismantle and clean them. They can be lubricated with petroleum jelly when re-assembling. It's also worth leaving out the zero rod. This makes zero open rather than short to cathode. This is the way all subsequent AVO testers did it.

see here
https://www.vintage-radio.net/forum/...ghlight=roller

Peter

David G4EBT · 6th Nov 2022, 12:46 pm

I wouldn't use WD40 on anything other than squeaky hinges, and nowhere near a radio or test gear. WD40 gets used for lots of things, (rarely, I suspect, for its original purpose), but to my mind, doesn't do any of them very well. It brings to mind the saying: 'if the only tool in your box is a hammer, everything starts to look like a nail'.

That said, WD40, (the company - not the yellow and blue aerosol can), does have other more suitable products, such as dry PTFE lubricant:

https://www.screwfix.com/p/wd-40-dry...E&gclsrc=aw.ds

Also, there is dry graphite powder too, used extensively to lubricate and free stuck locks. It's extremely fine, needs to be used sparingly, is very messy, but works very well as a dry lubricant for plastic components where oil and grease are best avoided. If a little puff of that on the roller switches didn't do the trick, at least it wouldn't do any harm:

https://www.amazon.co.uk/Kasp-K30050...00BTOBHH6&th=1

I have a Taylor 45D valve tester which has twelve roller switches, the last three of which I've never had to rotate for any conventional valve settings. If I was unlucky enough to have to dismantle any of the switches, I think I'd swap those three for any defective ones. I hope I never have to - it seems quite a palaver.

It seems to me that valve testers aren't so much 'test gear', as a hobby in their own right, and a 'money pit' too. I'm fortunate to have bought mine in the 70s when they languished unsold on bring and buy stands at rallies. Mine was a £20 impulse buy as I was leaving at 4pm. (That said, £20 in 1975 equates to £200 today, so not quite the bargain it might seem at first sight).

Good luck with the switches.

Matthew kane · 12th Nov 2022, 6:00 am

Also want to add my 2c that on some of the rotaries I've disassembled AVO may have one stage used some sort of grease which over time and use dries up to small bits of brittle wax flakes. I have found this in a few units, full disassembly, clean up and I have had to polish out the lip of each bakelite assembly with metal polish on the bench grinder.

woodchips · 13th Nov 2022, 11:45 am

I am restoring a Mk2, and some of the rotary switches were immovable. With lots of wafers, buried in the tester, I really didn't want to strip them down, had previous excitement with paxolin wafers disintegrating.

I used IPA in the end, removed the knob, put a drop on the spindle, and left them for weeks. Because I am only able to get to where they are stored every couple of months it did take 2 or 3 applications to get it moving, and longer to get it moving by finger power. With steel shafted switches you can use pretty brutal methods to get them moving, once a gap then the IPA can penetrate. Would point out that this is rotary switches, not the roller switches!

5th Nov 2022, 5:15 pm	#1
Viewmaster Hexode Join Date: Jul 2016 Location: Ashby de la Zouch, Leicestershire, UK. Posts: 253	AVO 2 panel valve tester stiff rotary switch I have one of these AVO panel testers, but the rotary switch that selects 0 -9 on each rotary, some are rather stiff to turn. I tried a little WD 40 but with little improvement. Sprayed both inside and outside the switches. Any ideas, please, how to ease the movement ? __________________ "One small step for man".....because he has arthritis. www.retinascope.co.uk Albert.

5th Nov 2022, 6:23 pm	#2
Stevie342000 Hexode Join Date: Jan 2006 Location: Greater Manchester, UK. Posts: 373	Re: AVO 2 panel valve tester stiff rotary switch Not sure it is advised to use WD40 anywhere near bakelite - google will tell you, google will also tell you dismantle the rollers but becareful....

5th Nov 2022, 6:40 pm	#3
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,465	Re: AVO 2 panel valve tester stiff rotary switch There are several threads on this forum regarding this so search the forum first. In general you shouldn't use anything to lubricate the roller selectors with, just dismantle them all and clean them thoroughly with IPA and put them back. Polishing some pieces with dry graphite powder/lubrication which you then remove again might help some pieces move more smoothly. Take care to not rub the white paint as it easily comes off. You can repaint it if you need but it is tedious work. Any lubrication will only let dust accumulate and make it into a goo that stiffens over time. __________________ Martin, Sweden

6th Nov 2022, 9:44 am	#4
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,294	Re: AVO 2 panel valve tester stiff rotary switch WD40 should NOT be used on the AVO roller switches, the only proper way is to fully dismantle and clean them. They can be lubricated with petroleum jelly when re-assembling. It's also worth leaving out the zero rod. This makes zero open rather than short to cathode. This is the way all subsequent AVO testers did it. see here https://www.vintage-radio.net/forum/...ghlight=roller Peter

6th Nov 2022, 12:46 pm	#5
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: AVO 2 panel valve tester stiff rotary switch I wouldn't use WD40 on anything other than squeaky hinges, and nowhere near a radio or test gear. WD40 gets used for lots of things, (rarely, I suspect, for its original purpose), but to my mind, doesn't do any of them very well. It brings to mind the saying: 'if the only tool in your box is a hammer, everything starts to look like a nail'. That said, WD40, (the company - not the yellow and blue aerosol can), does have other more suitable products, such as dry PTFE lubricant: https://www.screwfix.com/p/wd-40-dry...E&gclsrc=aw.ds Also, there is dry graphite powder too, used extensively to lubricate and free stuck locks. It's extremely fine, needs to be used sparingly, is very messy, but works very well as a dry lubricant for plastic components where oil and grease are best avoided. If a little puff of that on the roller switches didn't do the trick, at least it wouldn't do any harm: https://www.amazon.co.uk/Kasp-K30050...00BTOBHH6&th=1 I have a Taylor 45D valve tester which has twelve roller switches, the last three of which I've never had to rotate for any conventional valve settings. If I was unlucky enough to have to dismantle any of the switches, I think I'd swap those three for any defective ones. I hope I never have to - it seems quite a palaver. It seems to me that valve testers aren't so much 'test gear', as a hobby in their own right, and a 'money pit' too. I'm fortunate to have bought mine in the 70s when they languished unsold on bring and buy stands at rallies. Mine was a £20 impulse buy as I was leaving at 4pm. (That said, £20 in 1975 equates to £200 today, so not quite the bargain it might seem at first sight). Good luck with the switches. __________________ David. BVWS Member. G-QRP Club member 1339.

12th Nov 2022, 6:00 am	#6
Matthew kane Tetrode Join Date: May 2019 Location: Melbourne, Victoria, Australia. Posts: 66	Re: AVO 2 panel valve tester stiff rotary switch Also want to add my 2c that on some of the rotaries I've disassembled AVO may have one stage used some sort of grease which over time and use dries up to small bits of brittle wax flakes. I have found this in a few units, full disassembly, clean up and I have had to polish out the lip of each bakelite assembly with metal polish on the bench grinder.

13th Nov 2022, 11:45 am	#7
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,174	Re: AVO 2 panel valve tester stiff rotary switch I am restoring a Mk2, and some of the rotary switches were immovable. With lots of wafers, buried in the tester, I really didn't want to strip them down, had previous excitement with paxolin wafers disintegrating. I used IPA in the end, removed the knob, put a drop on the spindle, and left them for weeks. Because I am only able to get to where they are stored every couple of months it did take 2 or 3 applications to get it moving, and longer to get it moving by finger power. With steel shafted switches you can use pretty brutal methods to get them moving, once a gap then the IPA can penetrate. Would point out that this is rotary switches, not the roller switches!