UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Closed Thread
 
Thread Tools
Old 30th Nov 2020, 10:27 pm   #1
Ricardo
Pentode
 
Join Date: Jul 2006
Location: Bedfordshire, UK.
Posts: 211
Default AVO VCM MK4 meter movement transplant

I have recently completed the restoration of my AVO VCM MK4 valve tester. Although the original meter movement is still working it has some problems with the needle sticking mostly at around 80% of the scale. I would like to get the original meter refurbished if possible, but sadly Herts Meter Company can no longer undertake the work and I haven’t yet found anyone else with the necessary skills.

As such I decided to follow in the footsteps of others on this forum and replace it with a new Simpson 29T taut band rectangular meter with a 25µA movement. It is driven by a meter protection amplifier to a design posted elsewhere on the forum and constructed on a piece of Veroboard.

The greatest challenge for me was in producing the artwork for an AVO VCM meter scale to accurately align with the Simpson meter with its 100-degree deflection. As others have done before I spent quite a while learning how to use the excellent Galva scale drawing software package to produce the necessary scale artwork which I printed onto some decent quality inkjet paper and laminated.

I am attaching the following photos with this first post
1 & 2 = Rear mounting of Simpson Meter; 3 = Meter Protection Amplifier; 4 = Simpson Meter with VCM scale fitted

Click image for larger version

Name:	IMGP2511 sm.jpg
Views:	142
Size:	189.6 KB
ID:	221578 Click image for larger version

Name:	IMGP2512 sm.jpg
Views:	133
Size:	187.6 KB
ID:	221575 Click image for larger version

Name:	IMGP2510 sm.jpg
Views:	150
Size:	195.8 KB
ID:	221576 Click image for larger version

Name:	IMGP2517 sm.jpg
Views:	149
Size:	185.9 KB
ID:	221577

Richard
Ricardo is offline  
Old 30th Nov 2020, 10:30 pm   #2
Ricardo
Pentode
 
Join Date: Jul 2006
Location: Bedfordshire, UK.
Posts: 211
Default Re: AVO VCM MK4 meter movement transplant

I have also made a test plug fitted with some resistors between different valve pins to allow me to easily check the resistance scale of the VCM at several known points.

I am attaching the following photos with this second post

1 = Test plug with resistors fitted; 2 = VCM in Set Position; 3 = VCM with 1Mohm leakage; 4 = VCM with 25Mohm leakage

Click image for larger version

Name:	IMGP2500 sm.jpg
Views:	130
Size:	45.2 KB
ID:	221579 Click image for larger version

Name:	IMGP2504 sm.JPG
Views:	131
Size:	197.0 KB
ID:	221580 Click image for larger version

Name:	IMGP2505 sm.JPG
Views:	105
Size:	196.8 KB
ID:	221581 Click image for larger version

Name:	IMGP2506 sm.JPG
Views:	120
Size:	198.5 KB
ID:	221582

Richard
Ricardo is offline  
Old 30th Nov 2020, 11:03 pm   #3
trh01uk
Octode
 
trh01uk's Avatar
 
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,648
Default Re: AVO VCM MK4 meter movement transplant

Well, I can only say I am very impressed with the quality of your workmanship. I will be interested to hear what results you get with the unit.

Richard
trh01uk is online now  
Old 1st Dec 2020, 12:32 am   #4
Dekatron
Octode
 
Dekatron's Avatar
 
Join Date: May 2009
Location: Linkoping, Sweden
Posts: 1,463
Default Re: AVO VCM MK4 meter movement transplant

Really nice!
__________________
Martin, Sweden
Dekatron is offline  
Old 1st Dec 2020, 9:10 am   #5
chriswood1900
Octode
 
Join Date: Jan 2007
Location: Dorridge, West Midlands, UK.
Posts: 1,474
Default Re: AVO VCM MK4 meter movement transplant

Nice job and the Simpson movement looks just the right style for a period look to match the MK4.
__________________
Chris Wood
BVWS Member
chriswood1900 is online now  
Old 1st Dec 2020, 11:08 am   #6
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: AVO VCM MK4 meter movement transplant

Where did you find the Simpson movement?
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline  
Old 1st Dec 2020, 9:10 pm   #7
Ricardo
Pentode
 
Join Date: Jul 2006
Location: Bedfordshire, UK.
Posts: 211
Default Re: AVO VCM MK4 meter movement transplant

Thanks for all of the positive comments.

The meter I used is Simpson Part No. 03951.

It is a 4-1/2” Model 29T DC Taut-Band 0-25µA Microammeter.

I purchased it from Mouser Electronics in the UK and their Part No is 529-03951.

It was shipped from the USA and arrived within a couple of days – admittedly I bought it back in early February, pre-lockdown, so it might take a bit longer these days.

Richard
Ricardo is offline  
Old 4th Dec 2020, 6:32 pm   #8
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: AVO VCM MK4 meter movement transplant

I just looked it up, quite pricey!
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline  
Old 5th Dec 2020, 11:58 am   #9
John_BS
Octode
 
John_BS's Avatar
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
Default Re: AVO VCM MK4 meter movement transplant

Amazing job: well done.

Presumably you now have a master Galve file which others could use?
John
John_BS is offline  
Old 6th Dec 2020, 3:47 pm   #10
Ricardo
Pentode
 
Join Date: Jul 2006
Location: Bedfordshire, UK.
Posts: 211
Default Re: AVO VCM MK4 meter movement transplant

John,

The AVO VCM MK4 scale for the Simpson meter was drawn with F5BU's (Jean-Paul Gendner's) Galva software. The latest version of the program can be downloaded from his website f5bu.fr. I used version 3.00.

I used one of his example scales as a starting point together with scans of the Simpson meter scale.

Here is a PDF printout of the scale.

AVOvcmMK4.pdf

If you want a copy of the Galva code I can send it to you, but please be aware that I haven’t fully commented it or translated all of the original comments from French into English.


Richard
Ricardo is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:43 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.