Advance Electronics Ltd VM78A - UK Vintage Radio Repair and Restoration Discussion Forum

Manx Nick · 11th Mar 2019, 12:07 pm

Hi all,

I recently acquired this Advance Electronics Ltd VM78A AC Voltmeter.

Its in a rather bashed state but i was wondering if anyone knows more about it and what it is used for normally? (I am new to all of this)

I have looked inside and there appears to be three odd shaoped batteries, that have half leaked and popped inside the case, however they dont seem to have affected any other components.

I am looking to restore it but wondered if its of any significance?

Thanks,

Nick

Manx Nick · 11th Mar 2019, 12:42 pm

More pics

Skywave · 11th Mar 2019, 1:27 pm

Quote:

Originally Posted by Manx Nick

Advance Electronics Ltd VM78A AC Voltmeter.
Its in a rather bashed state but i was wondering if anyone knows more about it and what it is used for normally?

"What is was used for?" you ask.
A glance at the front panel tells you: a.c. voltages up to a frequency of 1 MHz; voltage ranges as per the switch on the right-hand side.
So it would have been used in various applications where the voltage to be measured fell within those two ranges.

For most uses, it would probably have used the a.c. mains to power it; the batteries would simply have been an alternative power source, making the item portable.

As for a manual for it, that is available from Telford Electronics:
http://www.telford-electronics.co.uk/manual.php?alpha=a

Once restored, it will be useful piece of test kit.

Al.

barrymagrec · 11th Mar 2019, 2:04 pm

I used to have one of these, it was the transistor replacement for the VM77 valve voltmeters which were better in some respects since they were mains powered and had a 4.5 MHz bandwidth.

It was a good meter in it`s day and the battery operation made it handy for on site work (I used to repair tape and film recording machines)

The limited bandwidth was no problem for audio work and it was sufficiently sensitive to measure noise well below -60 dbu.

The main problem was the cost of batteries, it used Mercury cells and the last time I bought a set, over thirty years ago, it cost more than £20.00.

Manx Nick · 11th Mar 2019, 3:43 pm

Hi thanks for the information and advice! I will post pics once its done. Thanks for the manual too.

So (and bear with me on this) how would you connect mains power to it? There isn't a socket for any power. Or have I missed the point?

barrymagrec · 11th Mar 2019, 4:06 pm

There was no facility to connect mains power and providing an external supply is complicated since the battery arrangement used 9 Mercury cells in series with at least one, possibly more, taps.

From memory each Mercury cell produced 1.35 volts and the stability made them attractive for many applications.

I think that Mercury cells of the size used in the VM78 are now prohibited due to the
toxicity of Mercury.

It would of course be possible to build a custom supply using, say LM317s to produce the various voltages.

gezza123 · 11th Mar 2019, 4:34 pm

Hi Nick.

You will find that forum member Phil G4SPZ did an excellent job on his:-

https://www.vintage-radio.net/forum/...d.php?t=123123

SO NO NEED TO INVENT A NEW WHEEL.

gezza123

David Simpson · 11th Mar 2019, 4:49 pm

Gezza, that photo isn't Phil's - its mine.
Nick, I've a spare chassis, I think, and some spare meters. Let me know if you need anything.

Regards, David

gezza123 · 11th Mar 2019, 4:58 pm

yes David sorry I did eventualy delete it.

Here is what I meant to put on.as part of my collection.

Gezza123

gezza123 · 11th Mar 2019, 5:30 pm

And just for you David they are in pride of place.

Thank you gezza123

Manx Nick · 11th Mar 2019, 9:06 pm

Thanks for all the information and help here. I will try to set up the batteries inside as suggested. It's quite battered, but this adds to the"patina of age"

David Simpson · 11th Mar 2019, 9:12 pm

Hey Gezza, that's a great collection. And - on shelves in your bedroom. Now I don't feel so guilty for doing the same.
I did have a heap of the blue cased 77's, ex uni lab, several years back. However, a guitar amp building chum used a few for building small training amps for guitar students he had. I did also acquire several 78's, and thought them reasonably accurate. Needing the mercury cell pack is a bind. So I just used some AA rechargeable cells as a temp measure.
I hope Nick gets his working OK.

Regards, David

Radio Wrangler · 11th Mar 2019, 9:39 pm

Don't feel so bad now about having an RA1217 as a bedside radio....

David

Manx Nick · 12th Mar 2019, 12:52 pm

So is that about 12v in all then? Could I rig up a battery pack holder for each compartment and solder that in?

Like this?

https://www.amazon.co.uk/SODIAL-Spri...J7TGZ71PMXS5XT

Manx Nick · 3rd May 2019, 2:50 pm

Quote:

Originally Posted by David Simpson

Gezza, that photo isn't Phil's - its mine.
Nick, I've a spare chassis, I think, and some spare meters. Let me know if you need anything.

Regards, David

Hi David,

Thank you for the offer - I could do with finding out the voltages of the batteries required and how I could rig up a battery pack or similar.

Any thoughts?

Thanks,

Nick

MotorBikeLes · 3rd May 2019, 10:09 pm

That is not simply an AC voltmeter, but as it says on the front, it is an RMS voltmeter. Probably a good meter in its day. If you clean up the chemical mess, you MAY find there is space to fit two of the 6v 2AHr lead acid batteries, which could be easily recharged, or simply get 8 NiMh cells (AA size) in suitable AA holders.
Les.

m0cemdave · 3rd May 2019, 10:23 pm

That battery container is familiar. Many years ago, I had a neat little portable voltmeter with an identical one. In those days it was still possible to get single Mercury cells and I managed to make up some sleeves, enabling them to be fitted.
But I'm sure the meter was an HP, not an Advance. Type 403A from memory, maybe?

11th Mar 2019, 12:07 pm	#1
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Advance Electronics Ltd VM78A Hi all, I recently acquired this Advance Electronics Ltd VM78A AC Voltmeter. Its in a rather bashed state but i was wondering if anyone knows more about it and what it is used for normally? (I am new to all of this) I have looked inside and there appears to be three odd shaoped batteries, that have half leaked and popped inside the case, however they dont seem to have affected any other components. I am looking to restore it but wondered if its of any significance? Thanks, Nick Attached Thumbnails

11th Mar 2019, 12:42 pm	#2
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Re: Advance Electronics Ltd VM78A More pics Attached Thumbnails

11th Mar 2019, 2:04 pm	#4
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,558	Re: Advance Electronics Ltd VM78A I used to have one of these, it was the transistor replacement for the VM77 valve voltmeters which were better in some respects since they were mains powered and had a 4.5 MHz bandwidth. It was a good meter in it`s day and the battery operation made it handy for on site work (I used to repair tape and film recording machines) The limited bandwidth was no problem for audio work and it was sufficiently sensitive to measure noise well below -60 dbu. The main problem was the cost of batteries, it used Mercury cells and the last time I bought a set, over thirty years ago, it cost more than £20.00. Last edited by barrymagrec; 11th Mar 2019 at 2:21 pm.

11th Mar 2019, 3:43 pm	#5
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Re: Advance Electronics Ltd VM78A Hi thanks for the information and advice! I will post pics once its done. Thanks for the manual too. So (and bear with me on this) how would you connect mains power to it? There isn't a socket for any power. Or have I missed the point? Last edited by Manx Nick; 11th Mar 2019 at 3:54 pm. Reason: Question

11th Mar 2019, 4:06 pm	#6
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,558	Re: Advance Electronics Ltd VM78A There was no facility to connect mains power and providing an external supply is complicated since the battery arrangement used 9 Mercury cells in series with at least one, possibly more, taps. From memory each Mercury cell produced 1.35 volts and the stability made them attractive for many applications. I think that Mercury cells of the size used in the VM78 are now prohibited due to the toxicity of Mercury. It would of course be possible to build a custom supply using, say LM317s to produce the various voltages.

11th Mar 2019, 4:34 pm	#7
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: Advance Electronics Ltd VM78A Hi Nick. You will find that forum member Phil G4SPZ did an excellent job on his:- https://www.vintage-radio.net/forum/...d.php?t=123123 SO NO NEED TO INVENT A NEW WHEEL. gezza123 Last edited by Station X; 11th Mar 2019 at 5:52 pm. Reason: Link added.

11th Mar 2019, 4:49 pm	#8
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,853	Re: Advance Electronics Ltd VM78A Gezza, that photo isn't Phil's - its mine. Nick, I've a spare chassis, I think, and some spare meters. Let me know if you need anything. Regards, David

11th Mar 2019, 4:58 pm	#9
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: Advance Electronics Ltd VM78A yes David sorry I did eventualy delete it. Here is what I meant to put on.as part of my collection. Gezza123 Attached Thumbnails

11th Mar 2019, 5:30 pm	#10
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: Advance Electronics Ltd VM78A And just for you David they are in pride of place. Thank you gezza123 Attached Thumbnails

11th Mar 2019, 9:06 pm	#11
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Re: Advance Electronics Ltd VM78A Thanks for all the information and help here. I will try to set up the batteries inside as suggested. It's quite battered, but this adds to the"patina of age"

11th Mar 2019, 9:12 pm	#12
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,853	Re: Advance Electronics Ltd VM78A Hey Gezza, that's a great collection. And - on shelves in your bedroom. Now I don't feel so guilty for doing the same. I did have a heap of the blue cased 77's, ex uni lab, several years back. However, a guitar amp building chum used a few for building small training amps for guitar students he had. I did also acquire several 78's, and thought them reasonably accurate. Needing the mercury cell pack is a bind. So I just used some AA rechargeable cells as a temp measure. I hope Nick gets his working OK. Regards, David

11th Mar 2019, 9:39 pm	#13
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,874	Re: Advance Electronics Ltd VM78A Don't feel so bad now about having an RA1217 as a bedside radio.... David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

12th Mar 2019, 12:52 pm	#14
Manx Nick Pentode Join Date: Jul 2014 Location: Isle of Man, UK. Posts: 102	Re: Advance Electronics Ltd VM78A So is that about 12v in all then? Could I rig up a battery pack holder for each compartment and solder that in? Like this? https://www.amazon.co.uk/SODIAL-Spri...J7TGZ71PMXS5XT

3rd May 2019, 10:09 pm	#16
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Advance Electronics Ltd VM78A That is not simply an AC voltmeter, but as it says on the front, it is an RMS voltmeter. Probably a good meter in its day. If you clean up the chemical mess, you MAY find there is space to fit two of the 6v 2AHr lead acid batteries, which could be easily recharged, or simply get 8 NiMh cells (AA size) in suitable AA holders. Les.

3rd May 2019, 10:23 pm	#17
m0cemdave Octode Join Date: Feb 2009 Location: Bletchley, Buckinghamshire, UK. Posts: 1,219	Re: Advance Electronics Ltd VM78A That battery container is familiar. Many years ago, I had a neat little portable voltmeter with an identical one. In those days it was still possible to get single Mercury cells and I managed to make up some sleeves, enabling them to be fitted. But I'm sure the meter was an HP, not an Advance. Type 403A from memory, maybe?