Testing rectifier with AVO MK1 - UK Vintage Radio Repair and Restoration Discussion Forum

Pete_kaye · 17th Aug 2017, 6:19 pm

I have a suspect 6X5GT from a Toaster radio. It only reads 180 V on the cathode target 260V. I tried to test it on AVO Mk1 tester yesterday but the instructions are unclear. I couldn't get a reading on either diode. Can anyone advise me?

PJL · 18th Aug 2017, 11:34 am

None of the testers do a particularly good job of testing rectifiers. The AVO 2-panel meter only does an emissions test.

If the set is taking the correct current and the dropper resistance is correct then you can assume the valve is low.

Phil G4SPZ · 20th Aug 2017, 10:23 pm

I can let you have a good 6X5GT for a couple of quid plus postage - drop me a PM.

The Avo twin-panel tester also measures gm, but not on rectifiers of course! It's a while since I used one but I remember that it tested rectifiers perfectly well.

David Simpson · 21st Aug 2017, 8:00 am

Just wondering - are we talking about an AVO VCM MK1, or a Twin-Panel Tester ? They are very different.

Regards, David

Pete_kaye · 21st Aug 2017, 1:45 pm

I was talking about a 1948 twin panel tester.

Phil G4SPZ · 22nd Aug 2017, 2:28 pm

Well, I amongst others was under the misapprehension that the twin-panel and the MkI were one and the same thing! Is it correct that the "AVO Valve Tester" referred to in the Avo valve data books is the twin-panel tester? The control settings would seem to confirm that.

Slightly OT I know, but if someone could post a picture of a VCM Mk I it would clarify the situation.

Pete, your valve's in the post!

David Simpson · 22nd Aug 2017, 3:23 pm

Hi Phil & Pete,
The designations of AVO's range has raised queries a number of times over the years.
The photographs at the front of the AVO Valve Data Manual clearly list the centre picture as "Valve Characteristic Meter. Mk's 1 & 2" i/e. VCM Mk1 & VCM Mk2.
The bottom r/h picture is just called "Avo Valve Tester". Known colloquially as "The Two Panel" amongst the vintage fraternity.
Likewise, in the valve data pages - r/h side - there is a separate tabulation of settings called "DATA FOR AVO VALVE TESTER".
Very confusing I know. Some folk do refer to the Two Panel as Valve Tester No1.

Regards, David

Phil G4SPZ · 22nd Aug 2017, 6:11 pm

David, it probably depends on which edition of the AVO Valve Data Book you're looking at! Mine only shows a picture of the VCM Mk III, probably the current model at the time the book was published.

neil24-7 · 22nd Aug 2017, 6:56 pm

Borrowed from the net, a picture of an avo vcm mk1 and a mk 11 together

Phil G4SPZ · 22nd Aug 2017, 7:00 pm

Thanks Neil

17th Aug 2017, 6:19 pm	#1
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Testing rectifier with AVO MK1 I have a suspect 6X5GT from a Toaster radio. It only reads 180 V on the cathode target 260V. I tried to test it on AVO Mk1 tester yesterday but the instructions are unclear. I couldn't get a reading on either diode. Can anyone advise me?

18th Aug 2017, 11:34 am	#2
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Testing rectifier with AVO MK1 None of the testers do a particularly good job of testing rectifiers. The AVO 2-panel meter only does an emissions test. If the set is taking the correct current and the dropper resistance is correct then you can assume the valve is low.

20th Aug 2017, 10:23 pm	#3
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Testing rectifier with AVO MK1 I can let you have a good 6X5GT for a couple of quid plus postage - drop me a PM. The Avo twin-panel tester also measures gm, but not on rectifiers of course! It's a while since I used one but I remember that it tested rectifiers perfectly well. __________________ Phil Optimist [n]: One who is not in possession of the full facts

21st Aug 2017, 8:00 am	#4
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,851	Re: Testing rectifier with AVO MK1 Just wondering - are we talking about an AVO VCM MK1, or a Twin-Panel Tester ? They are very different. Regards, David

21st Aug 2017, 1:45 pm	#5
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Testing rectifier with AVO MK1 I was talking about a 1948 twin panel tester.

22nd Aug 2017, 2:28 pm	#6
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Testing rectifier with AVO MK1 Well, I amongst others was under the misapprehension that the twin-panel and the MkI were one and the same thing! Is it correct that the "AVO Valve Tester" referred to in the Avo valve data books is the twin-panel tester? The control settings would seem to confirm that. Slightly OT I know, but if someone could post a picture of a VCM Mk I it would clarify the situation. Pete, your valve's in the post! __________________ Phil Optimist [n]: One who is not in possession of the full facts

22nd Aug 2017, 3:23 pm	#7
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,851	Re: Testing rectifier with AVO MK1 Hi Phil & Pete, The designations of AVO's range has raised queries a number of times over the years. The photographs at the front of the AVO Valve Data Manual clearly list the centre picture as "Valve Characteristic Meter. Mk's 1 & 2" i/e. VCM Mk1 & VCM Mk2. The bottom r/h picture is just called "Avo Valve Tester". Known colloquially as "The Two Panel" amongst the vintage fraternity. Likewise, in the valve data pages - r/h side - there is a separate tabulation of settings called "DATA FOR AVO VALVE TESTER". Very confusing I know. Some folk do refer to the Two Panel as Valve Tester No1. Regards, David

22nd Aug 2017, 6:11 pm	#8
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Testing rectifier with AVO MK1 David, it probably depends on which edition of the AVO Valve Data Book you're looking at! Mine only shows a picture of the VCM Mk III, probably the current model at the time the book was published. __________________ Phil Optimist [n]: One who is not in possession of the full facts

22nd Aug 2017, 6:56 pm	#9
neil24-7 Tetrode Join Date: Jan 2016 Location: Jarrow, Tyne and Wear, UK. Posts: 81	Re: Testing rectifier with AVO MK1 Borrowed from the net, a picture of an avo vcm mk1 and a mk 11 together Attached Thumbnails

22nd Aug 2017, 7:00 pm	#10
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Testing rectifier with AVO MK1 Thanks Neil __________________ Phil Optimist [n]: One who is not in possession of the full facts