AVO VCM Mk II - UK Vintage Radio Repair and Restoration Discussion Forum

G1RAO keith · 26th Aug 2018, 4:46 pm

Hi All
Having stripped down the roller switch on my AVO mkii Last year it's starting to stick on a couple of the switches one of them in fact will only go one way,I am not bothered about stripping in down again I was just wondering if anyone has done one before and is it a good idea to lightly grease the internal parts or is it a case of I wish I hadn't done that.keith

The Philpott · 27th Aug 2018, 2:06 pm

The rotary selector switches? Which model- 7,8,9 or 40 i'm guessing..?

There are 2 places jamming can occur, a) in the sliding electrical contacts.The tolerances are quite fine and if an arc occurs they can repeatedly lock up at the same point. b) swarf or carborundum fragments lodged under the front of the switch can cause the ball and spring assy. to grate against the switch knob. On stripdown the little balls always make a bid for freedom just when you least expect it.

My one experience of this total switch dismantlement is based on an old meter (1948) but similar mechanism seems to carry through onto later models. I had to knock the taper pins out of the switches, it was quite involved. I did use a small amount of grease to ease the reciprocal action of the balls and springs.

Flushing with wd40 is verboten as it will only make things worse!

Tip- only dismantle one switch at a time..

Dave

G1RAO keith · 27th Aug 2018, 5:13 pm

Hi Dave
Thanks for the reply sorry this is my fault i should have explained it better this is an AVO vcm.it's the edgewise valve pin selector switches on the top of the tester nine in total and yes I have cleaned the front panel switches and guess what a cheaky little steel ball flew across the room at the speed of light,I did find it eventually.i used a small amount of oil on the spring leaf that holds the ball barings,the contacts I have cleaned in the past.regards keith

Sinewave · 27th Aug 2018, 5:15 pm

Is this a valve tester?

G1RAO keith · 27th Aug 2018, 5:19 pm

Hi
Yes just edited my last post AVO mkii vcm.

AC/HL · 27th Aug 2018, 5:55 pm

Thread title updated

26th Aug 2018, 4:46 pm	#1
G1RAO keith Pentode Join Date: Mar 2008 Location: Bury, Lancashire, UK. Posts: 138	AVO VCM Mk II Hi All Having stripped down the roller switch on my AVO mkii Last year it's starting to stick on a couple of the switches one of them in fact will only go one way,I am not bothered about stripping in down again I was just wondering if anyone has done one before and is it a good idea to lightly grease the internal parts or is it a case of I wish I hadn't done that.keith

27th Aug 2018, 2:06 pm	#2
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,108	Re: AVO Mk II The rotary selector switches? Which model- 7,8,9 or 40 i'm guessing..? There are 2 places jamming can occur, a) in the sliding electrical contacts.The tolerances are quite fine and if an arc occurs they can repeatedly lock up at the same point. b) swarf or carborundum fragments lodged under the front of the switch can cause the ball and spring assy. to grate against the switch knob. On stripdown the little balls always make a bid for freedom just when you least expect it. My one experience of this total switch dismantlement is based on an old meter (1948) but similar mechanism seems to carry through onto later models. I had to knock the taper pins out of the switches, it was quite involved. I did use a small amount of grease to ease the reciprocal action of the balls and springs. Flushing with wd40 is verboten as it will only make things worse! Tip- only dismantle one switch at a time.. Dave

27th Aug 2018, 5:13 pm	#3
G1RAO keith Pentode Join Date: Mar 2008 Location: Bury, Lancashire, UK. Posts: 138	Re: AVO Mk II Hi Dave Thanks for the reply sorry this is my fault i should have explained it better this is an AVO vcm.it's the edgewise valve pin selector switches on the top of the tester nine in total and yes I have cleaned the front panel switches and guess what a cheaky little steel ball flew across the room at the speed of light,I did find it eventually.i used a small amount of oil on the spring leaf that holds the ball barings,the contacts I have cleaned in the past.regards keith Last edited by G1RAO keith; 27th Aug 2018 at 5:17 pm. Reason: Memory loss in me

27th Aug 2018, 5:15 pm	#4
Sinewave Octode Join Date: May 2016 Location: Oxfordshire/Bucks borders, UK. Posts: 1,604	Re: AVO Mk II Is this a valve tester? __________________ Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.

27th Aug 2018, 5:19 pm	#5
G1RAO keith Pentode Join Date: Mar 2008 Location: Bury, Lancashire, UK. Posts: 138	Re: AVO Mk II Hi Yes just edited my last post AVO mkii vcm.

27th Aug 2018, 5:55 pm	#6
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: AVO VCM Mk II Thread title updated