AVO instructions for creating a standardised valve. - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

waran2005 · 14th Feb 2023, 1:31 pm

Hi Bazz,

Spot on lol, my 81 is new old stock and both halves are very different, nowhere near matched! I will have to get a few more ECC 80s to play with if they're pretty cheap.

Cheers.

Bazz4CQJ · 14th Feb 2023, 4:56 pm

You don't have to use an ECC81, but it has advantages for the 163. I've also used EF91's and ECL80's in the past. To begin with, anything you can trust would be helpful.

B

David Simpson · 14th Feb 2023, 5:15 pm

Waran, what you are experiencing with your ECC valves having different Ia's between the two triode halves, is also experienced by many valve testing enthusiasts. Also, they are susceptible to their Ia's running away if Vg is accidently set too low. Phut - they light up like a firework. Those reasons are why I changed to a more robust valve such as the 6AQ5 or 6AU5 for my standardising endeavours. If you've a box of cheapo EEC81's or 88's then by all means play with them. But decent ECC83's, E288CC's, etc., & top end brands like Telefunken are worth good money.
When tabulating Ia/Vg to be able to plot the Gm curve - ALWAYS start with a high Vg - just enough to obtain an Ia of 0.5mA or so, then reduce the Vg by small incremental voltage values & observe & record the gentle rise in Ia.
Also, it is essential, standardising-wise, that a valve which requires say - 6.3V - gets just that spot-on value.

Regards, David

Bazz4CQJ · 14th Feb 2023, 5:38 pm

Quote:

Originally Posted by David Simpson

Waran, what you are experiencing with your ECC valves having different Ia's between the two triode halves, is also experienced by many valve testing enthusiasts. Also, they are susceptible to their Ia's running away if Vg is accidently set too low. Phut - they light up like a firework. Those reasons are why I changed to a more robust valve such as the 6AQ5 or 6AU5 for my standardising endeavours.
Regards, David

You can make that argument about using rugged valves, but you can also make the argument that both for the benefit of the valve tester, and for all the valves you put on it, you need to have "switched on and fully warmed up yourself" in advance. Failure to do that is one reason why so many valve testers get phutted

. In any case, having a number of standard valves is good (including one which suits the lowest ranges) just in case one does go 'missing'. Certainly, on a 163, many/most of the valves you are likely to want to test will be on the low range of Gm and probably Ia.

B

woodchips · 16th Feb 2023, 10:52 am

Interesting bit in the Service And Calibration document for the Avo Valve Tester Type 160 about standardising valves. This is the reprint by Ed van der Weele, no date.

dazzlevision · 16th Feb 2023, 12:09 pm

Quote:

Originally Posted by woodchips

This is the reprint by Ed van der Weele, no date.

Bazz4CQJ · 16th Feb 2023, 6:32 pm

I checked Google for Mr van der Weele.....and found only this thread. His name shows up on radiomuseum.org but with no content.

The thing about standard valves for use with valve testers in that it's not rocket science, and it's been discussed on the forum in a number of threads.

David Simson started a "project" some years ago in which he carefully created a number of Standard valves "by hand" (not on a tester, but on a simple "text book" bench set up) and generously circulated then around the forum. The outcome suggested that most peoples' testers were working well. I think his choice of valve for that was simply a valve of which he had several available.

Ultimately, any valve will do, though some may suit different testers more than others. Think also about the type of valves you want to test.

There was a guy in France selling "standard valves", but I much believe that making your own is an informative exercise.

B

woodchips · 17th Feb 2023, 4:21 pm

When I found my copy of the van der Weele document in amongst all the rest of the valve tester paperwork I rather assumed it came off this forum, being the source of very much good info on said testers. It would seem I am wrong, and a search has so far not turned up an electronic copy. My guess is it is from about 6-8 years ago when I bought an Avo Mk2 off this forum, and wanted to know how to use it.

From this document there certainly aren't any secrets in making a standard valve, use DC supplies, well smoothed, to measure the gm at Ia=16mA, or graph the curve around 16mA. Any other valve, any other Ia likewise.

David Simpson · 18th Feb 2023, 11:57 am

As Bazz says, some years back I acquired a number of NOS & decent 2nd hand 6AQ5's & 6AU5's. These lent themselves to that particular standardising project. Their Ia/Vg curves could be plotted from a mA or so all the way up to 40 - 50mA. Most amplifying valves used in vintage domestic radios fall into this range of Ia. However, the wee ECC's only operate at 10mA or less. At the end of the calibration section in the AVO MK3, 4 & CT160's Manuals - they recommend using a large pentode to check the tester's Ia capabilities, anyway.
My pure DC testing rig has actually graphed up to 117mA Ia for an EL37, and regularly in the past tested KT66's & 88's up to 100mA Ia.
However, there is now a growing wee band of valve testing enthusiasts on the Forum who have ultra modern curve tracing rigs, (RoeTest, Sussex, etc.,) who can do the same standardisation in just a few minutes. Hopefully, they can pass around a few valves, and give my A4 graph-tracing wrist a rest.
There is still a bit of confusion about the difference between "Valve Testers" & "VCM's"(Valve Characteristic Meters). The Mullard HSVT & the CT160 are Testers. I.e. - they give a decent "pass" reading at the centre of the "Green Zone". Whereas the AVO MK's 1,2,3,4 & 163 give a dialled readout of mA/V, as well as an Ia reading, which is hopefully close to the VD Manual's. All would still benefit from being checked with a DC standardised valve, from time to time.

Regards, David

woodchips · 11th Mar 2023, 11:09 am

Came across an interesting section in Engineering Electronics by Ryder about standardising valves, see attached.

One of those interesting books, I bought it because of the chapter on induction heating, but lots of other interesting, ie sit and read it, bits.

Bazz4CQJ · 11th Mar 2023, 3:56 pm

I've created a few standard valves over the years and have always been happy with simple DC measurements, and I think David Simpson also goes down the DC route.

I suspect that anything else (AF methods) gets more complicated and I'm not sure what benefits it offers.

I'm inclined to say that the more basic the test, the fewer the sources of errors?

B

Waverider · 26th Apr 2023, 10:02 pm

This thread has been fascinating for me to read, I have an Avo VCM Mk II that I have been restoring and I have been wondering about measuring up a standardised valve. I also have an etracer computerised curve tracer, reading through the thread I realised that rather than building a rig to plot the curve I can instead use my etracer to make a few standardised valves for AVO calibration checking. I will try making up some etracer tube config files especially for this purpose and see how it goes. I have some 6AQ5's here and some ECC81 and ECC83's so it will be interesting to try them all.

14th Feb 2023, 1:31 pm	#21
waran2005 Tetrode Join Date: Feb 2020 Location: Cardiff, Wales, UK. Posts: 65	Re: AVO instructions for creating a standardised valve. Hi Bazz, Spot on lol, my 81 is new old stock and both halves are very different, nowhere near matched! I will have to get a few more ECC 80s to play with if they're pretty cheap. Cheers.

14th Feb 2023, 4:56 pm	#22
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO instructions for creating a standardised valve. You don't have to use an ECC81, but it has advantages for the 163. I've also used EF91's and ECL80's in the past. To begin with, anything you can trust would be helpful. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

14th Feb 2023, 5:15 pm	#23
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,853	Re: AVO instructions for creating a standardised valve. Waran, what you are experiencing with your ECC valves having different Ia's between the two triode halves, is also experienced by many valve testing enthusiasts. Also, they are susceptible to their Ia's running away if Vg is accidently set too low. Phut - they light up like a firework. Those reasons are why I changed to a more robust valve such as the 6AQ5 or 6AU5 for my standardising endeavours. If you've a box of cheapo EEC81's or 88's then by all means play with them. But decent ECC83's, E288CC's, etc., & top end brands like Telefunken are worth good money. When tabulating Ia/Vg to be able to plot the Gm curve - ALWAYS start with a high Vg - just enough to obtain an Ia of 0.5mA or so, then reduce the Vg by small incremental voltage values & observe & record the gentle rise in Ia. Also, it is essential, standardising-wise, that a valve which requires say - 6.3V - gets just that spot-on value. Regards, David

16th Feb 2023, 10:52 am	#25
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,175	Re: AVO instructions for creating a standardised valve. Interesting bit in the Service And Calibration document for the Avo Valve Tester Type 160 about standardising valves. This is the reprint by Ed van der Weele, no date.

16th Feb 2023, 6:32 pm	#27
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO instructions for creating a standardised valve. I checked Google for Mr van der Weele.....and found only this thread. His name shows up on radiomuseum.org but with no content. The thing about standard valves for use with valve testers in that it's not rocket science, and it's been discussed on the forum in a number of threads. David Simson started a "project" some years ago in which he carefully created a number of Standard valves "by hand" (not on a tester, but on a simple "text book" bench set up) and generously circulated then around the forum. The outcome suggested that most peoples' testers were working well. I think his choice of valve for that was simply a valve of which he had several available. Ultimately, any valve will do, though some may suit different testers more than others. Think also about the type of valves you want to test. There was a guy in France selling "standard valves", but I much believe that making your own is an informative exercise. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

17th Feb 2023, 4:21 pm	#28
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,175	Re: AVO instructions for creating a standardised valve. When I found my copy of the van der Weele document in amongst all the rest of the valve tester paperwork I rather assumed it came off this forum, being the source of very much good info on said testers. It would seem I am wrong, and a search has so far not turned up an electronic copy. My guess is it is from about 6-8 years ago when I bought an Avo Mk2 off this forum, and wanted to know how to use it. From this document there certainly aren't any secrets in making a standard valve, use DC supplies, well smoothed, to measure the gm at Ia=16mA, or graph the curve around 16mA. Any other valve, any other Ia likewise.

18th Feb 2023, 11:57 am	#29
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,853	Re: AVO instructions for creating a standardised valve. As Bazz says, some years back I acquired a number of NOS & decent 2nd hand 6AQ5's & 6AU5's. These lent themselves to that particular standardising project. Their Ia/Vg curves could be plotted from a mA or so all the way up to 40 - 50mA. Most amplifying valves used in vintage domestic radios fall into this range of Ia. However, the wee ECC's only operate at 10mA or less. At the end of the calibration section in the AVO MK3, 4 & CT160's Manuals - they recommend using a large pentode to check the tester's Ia capabilities, anyway. My pure DC testing rig has actually graphed up to 117mA Ia for an EL37, and regularly in the past tested KT66's & 88's up to 100mA Ia. However, there is now a growing wee band of valve testing enthusiasts on the Forum who have ultra modern curve tracing rigs, (RoeTest, Sussex, etc.,) who can do the same standardisation in just a few minutes. Hopefully, they can pass around a few valves, and give my A4 graph-tracing wrist a rest. There is still a bit of confusion about the difference between "Valve Testers" & "VCM's"(Valve Characteristic Meters). The Mullard HSVT & the CT160 are Testers. I.e. - they give a decent "pass" reading at the centre of the "Green Zone". Whereas the AVO MK's 1,2,3,4 & 163 give a dialled readout of mA/V, as well as an Ia reading, which is hopefully close to the VD Manual's. All would still benefit from being checked with a DC standardised valve, from time to time. Regards, David

11th Mar 2023, 11:09 am	#30
woodchips Octode Join Date: May 2010 Location: Grantham, Lincolnshire, UK. Posts: 1,175	Re: AVO instructions for creating a standardised valve. Came across an interesting section in Engineering Electronics by Ryder about standardising valves, see attached. One of those interesting books, I bought it because of the chapter on induction heating, but lots of other interesting, ie sit and read it, bits. Attached Thumbnails

11th Mar 2023, 3:56 pm	#31
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO instructions for creating a standardised valve. I've created a few standard valves over the years and have always been happy with simple DC measurements, and I think David Simpson also goes down the DC route. I suspect that anything else (AF methods) gets more complicated and I'm not sure what benefits it offers. I'm inclined to say that the more basic the test, the fewer the sources of errors? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

26th Apr 2023, 10:02 pm	#32
Waverider Diode Join Date: Apr 2023 Location: Melbourne, Victoria, Australia. Posts: 6	Re: AVO instructions for creating a standardised valve. This thread has been fascinating for me to read, I have an Avo VCM Mk II that I have been restoring and I have been wondering about measuring up a standardised valve. I also have an etracer computerised curve tracer, reading through the thread I realised that rather than building a rig to plot the curve I can instead use my etracer to make a few standardised valves for AVO calibration checking. I will try making up some etracer tube config files especially for this purpose and see how it goes. I have some 6AQ5's here and some ECC81 and ECC83's so it will be interesting to try them all.