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Old 12th Aug 2017, 6:42 pm   #61
Fourlegsgood
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Default Re: Free Standardised Valves

I realise that paper tables and graphs will soon run out of space so I wondered about a spreadsheet version and graph. Unfortunately whilst I am very much at home with CAD and Graphics applications I am not very good with spreadsheets beyond normal stuff.

This is my attempt. Maybe some one can do a template that we could attach to each valve and fill it in as it goes on its travels?

Nick

6AU5GT Nr 1 spreadsheet.pdf
valve 1.xlsx
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Old 12th Aug 2017, 7:57 pm   #62
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Default Re: Free Standardised Valves

Nick & Guys. There are now three different software graph responses to my original old fashioned A4 graph paper Gm graphs, for all the valves I've put out. Equally though, other folk are just using my graphs.
Old fashioned I might be, but I don't have the software, and I suspect many other Forum folk don't either. Hence the simplicity. "Singing from the same hymn sheet" is the quotation which comes to mind. If folk want to keep their Tester/VCM records in a spreadsheet format, then great. Otherwise it means that myself & others will have to spend time fannying about transposing results to study. (Note - study, not gloat).
Don't forget - I repeat - this is not a " My Tester is better than other folk's" competition. If one set of Gm graphs differ significantly from others - for the same valve, then there might well be a calibration issue. In that case - do a "before & after" graph, repair/calibration-wise. Letting us all know what was done would help folk who own the same tester or VCM & would appreciate this sharing of info in the future.
Don't worry about me hunched over a drawing board. I enjoy it. Keeps my brain active, & wrist & fingers co-ordination supple. (There is a joke about ex RAF guys in there). Admitted - I've a drawer full of professional drawing pens, ink, stencils, Rotring/Staedeter/Faber Castel, etc. And used them extensively in a pre-retirement life. Admitted - my graphs could be a tad neater, but all this constant voltage & current observations & tabulations - is jolly time consuming. Time is what I'm short of, I'm afraid. But my graphs, using 15 or 16 points, do reveal reasonable curves.
As I've already said a few posts back - once this project has run its course, maybe a few months, or a year or so, and the valves have passed from folk to folk to folk - then perhaps an acceptable software program could be used( Hey - Barry, Martin, Nick - who's going to donate hours & hours of time to transpose what- 25, 50, 100 other Forum folk's graphs ??)

Regards, David
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Old 12th Aug 2017, 8:04 pm   #63
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Default Re: Free Standardised Valves

I made a similar Excel sheet but used yours and added my info, however I moved the diagram to a separate sheet to keep the data on another sheet.

When the 6AU5GT arrived to me it was unfortunately damaged, there was a short between G1 and the Cathode. While examining the valve I could see that the cathode had fallen down through the top mica sheet and was tilting to one side. Some hard banging of the valve in my hand moved the cathode to the side enough so that it is almost centered but I couldn't get it to come through the mica sheet at the top.

The measurements in my VCM163 and Roetest V9 shows that the results are in line with Davids and I added them to the Excel-sheet. I made measurements with both Anode voltage set at 200V like in the AVO VDMs and also with 250V like David used. I only made measurements at 250V with the Roetest. With my VCM163 and a grid voltage of -20V I got a Gm of 4.4mA/V @ 46mA Ia with 200V and 4.6mA/V @ 49mA Ia at 250V. The Roetest used a grid voltage of -22.5V and there I got a Gm of 3.9 @ 39mA. I'll add my measurements to Davids sheet when I have some more time and post a scan here.

I will test a bunch of 6CH6/EL821 that are NOS unopened in their Pinnacle boxes and ship to David so that he can send them out to people for further testing. Hopefully I'll be able to include two used 6AU5GTs that show similar results to Davids.
Attached Files
File Type: xlsx Valves.xlsx (15.8 KB, 20 views)
File Type: pdf Valves.pdf (42.9 KB, 25 views)
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Last edited by Dekatron; 12th Aug 2017 at 8:06 pm. Reason: Added a PDF
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Old 12th Aug 2017, 8:12 pm   #64
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Default Re: Free Standardised Valves

Quote:
Originally Posted by David Simpson View Post
As I've already said a few posts back - once this project has run its course, maybe a few months, or a year or so, and the valves have passed from folk to folk to folk - then perhaps an acceptable software program could be used( Hey - Barry, Martin, Nick - who's going to donate hours & hours of time to transpose what- 25, 50, 100 other Forum folk's graphs ??)

Regards, David
Hopefully it won't take that much time if people just put down the numbers in a row, then they can easily be incorporated into an Excel-sheet.

I'll help out when I can.

Here's the data from the Excel sheet I just added:

Grid voltage 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15
D C tester 11 13,5 16 19 21,5 24,5 29 32 36 40,5 45 50 55,5 60,5 67 73,5
David Mk3 10 12,5 15 17,7 21 24 27 30 34 38 42 45,5 50 54,5 59,5 64
Richard Mk4 7,8 9,8 12 14,2 17,3 20,6 23,5 26 30 34 38 43 48 54 59 64,5
Nick VCM163 11 13 16 18,5 22 25 28 32 36 41 45 51 56 62 68 74
Martin VCM163 Va=200 14 15 18 20 23 27 30 34 38 42 46 52 57 63 69 76
Martin VCM163 Va=250 15 16 19 22 25 28 32 35 39 44 48 54 59 65 72 79
Martin Roetest V9 14,8 17 19,7 22,5 25,5 28,7 31,6 35 39,3 43,5 48 52,9 57,9 63,4 69,2 75,2

If you just add your own data at the end and some prefix text it is very easy to just add those rows to the Excel sheet.

Then someone can print that sheet and for instance just use a few datasets at a time to make it eligible. Marking which valve has been tested in a separate column can also be used to plot different valves in different diagrams.
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Old 12th Aug 2017, 8:51 pm   #65
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Default Re: Free Standardised Valves

Quote:
Originally Posted by Dekatron View Post
The measurements in my VCM163 and Roetest V9 shows that the results are in line with Davids and I added them to the Excel-sheet. I made measurements with both Anode voltage set at 200V like in the AVO VDMs and also with 250V like David used. I only made measurements at 250V with the Roetest. With my VCM163 and a grid voltage of -20V I got a Gm of 4.4mA/V @ 46mA Ia with 200V and 4.6mA/V @ 49mA Ia at 250V. The Roetest used a grid voltage of -22.5V and there I got a Gm of 3.9 @ 39mA. I'll add my measurements to Davids sheet when I have some more time and post a scan here.
I forgot to say that my measurements were made with Va = 250v because I just followed David's lead.

Nck
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Old 12th Aug 2017, 8:58 pm   #66
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Default Re: Free Standardised Valves

Quote:
Originally Posted by David Simpson View Post
Nick & Guys. There are now three different software graph responses to my original old fashioned A4 graph paper Gm graphs, for all the valves I've put out. Equally though, other folk are just using my graphs.
Old fashioned I might be, but I don't have the software, and I suspect many other Forum folk don't either. Hence the simplicity. "Singing from the same hymn sheet" is the quotation which comes to mind. If folk want to keep their Tester/VCM records in a spreadsheet format, then great. Otherwise it means that myself & others will have to spend time fannying about transposing results to study. (Note - study, not gloat).
David,

Don't get me wrong. I prefer the paper version and find easier to see what is what. It was just that the columns for figures was running out of room on the piece of paper.

regards, Nick
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Old 12th Aug 2017, 9:45 pm   #67
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Default Re: Free Standardised Valves

Guys, what Martin & Nick have done & the time spent - I'm really grateful. Very professional.
I could possibly reduce the width of the tabulation columns so that extra readings could be taken. I've that heap of Neil's 6AQ5's, and now Martin's kind offer of a donation of 6CH6's, still to do - so will commence with them. But not this week or next - harvest time - DIY time etc.
One wee niggle regarding Nick's & Martin's software graphs :- the size of the writing, particularly the tiny curve ID's beneath the x axis of Vg. Even with my glasses on - I'm struggling to read the info. Going by the age profile of many Forum folk - eyesight usage of glasses is probably prevalent amongst a heap of us retired guys.
I reiterate - many many thanks to all who are participating, and their time spent.
I might, just might, if this god-awful weather continues - send a wee handful of 6AQ5's & graphs down to Goldborne via Mark James(Another very hardworking agricultural/outdoor Forum guy), to be freely distributed. It will save postage costs.

Regards, David
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Old 13th Aug 2017, 6:27 am   #68
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Default Re: Free Standardised Valves

Quote:
Originally Posted by David Simpson View Post
One wee niggle regarding Nick's & Martin's software graphs :- the size of the writing, particularly the tiny curve ID's beneath the x axis of Vg. Even with my glasses on - I'm struggling to read the info.
Sorted (hopefully). See attached version 2.

regards, Nick

Valves-2.pdf

Valves-2.xlsx

Last edited by Fourlegsgood; 13th Aug 2017 at 6:48 am.
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Old 13th Aug 2017, 9:59 am   #69
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Default Re: Free Standardised Valves

Nick - many thanks for the revision. I can print off a nice pdf copy, but not the other - I don't have MS Office.
It would seem that the Roetest, my DC Tester, and the 163's are jolly close, but the older Mk3 & Mk4 struggle at achieving the higher Ia's. The Roetest's curve is mathematically perfect, but all the others exhibit the slight kinks.The kinks, I suspect, going by my own experience & some feedback from participants, are due to several factors. They are :- a) Wear & tear on Grid pots, b) switching between ranges on the grid volts switch & the meter switch's Ia range, c) age related deterioration of pots, shunts & multipliers, d) plain old human error(remember what I said last night about older Forum folk wearing glasses), e) the dynamics of the valve. My DC tester also meters Screen current, and I note with the 6AU5GT's that current starts to flow slightly round about -26/25 V Vg, and finally draws approx. 3 to 4mA in the -17/15V range.
The uploading & downloading of graphs & scanned copies of graphs, via the Forum, and to a lesser degree via emails, is obviously degrading the centimetric & millimetric matrices of the graphs. Thankfully Nick has enlarged the writing. Before - Jag inter lasa sma skrivand po graf papper, lodsen. That's for Martin when he arises from his pit & reads the post.

Regards, David
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Old 13th Aug 2017, 4:31 pm   #70
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Default Re: Free Standardised Valves

David, you may not have micro$oft Office, nor do I, but you can download LIBRE OFFICE, an open source "open document format" programme. I opens (most) stuff perfectly that was written in MS Office. Including the previous graph!
It is FREE, safe, and works. I have been using Libre and its predecessor Open Office.Org for maybe 15 years. OK with Windoze and Linux (my OS of choice) and probably Apple and Android as well.
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Old 13th Aug 2017, 5:53 pm   #71
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Default Re: Free Standardised Valves

Quote:
Originally Posted by David Simpson View Post
Nick - many thanks for the revision. I can print off a nice pdf copy, but not the other - I don't have MS Office.
It would seem that the Roetest, my DC Tester, and the 163's are jolly close, but the older Mk3 & Mk4 struggle at achieving the higher Ia's. The Roetest's curve is mathematically perfect, but all the others exhibit the slight kinks.The kinks, I suspect, going by my own experience & some feedback from participants, are due to several factors. They are :- a) Wear & tear on Grid pots, b) switching between ranges on the grid volts switch & the meter switch's Ia range, c) age related deterioration of pots, shunts & multipliers, d) plain old human error(remember what I said last night about older Forum folk wearing glasses), e) the dynamics of the valve. . . . . . .
David,

As you will know, the VCM163 grid voltage is set by a pot with the line on a see through (ish) plastic disc. The see through plastic disc is also some distance off the scale behind so parallax is almost guaranteed. I personally find it difficult to set that pot with any degree of accuracy and so if I want repeatable test results I set the grid volts by measurement on a DMM. Any kinks in my graph line are quite likely due to my imprecise setting of the grid volts.

That being said, I am impressed by the level of consistentcy of the results from all the testers. I have not worked it out but by eye it looks like plus or minus 5% which is fair enough.

regards, Nick

Last edited by Fourlegsgood; 13th Aug 2017 at 6:13 pm.
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Old 14th Aug 2017, 8:49 am   #72
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Default Re: Free Standardised Valves

Nick,

I'm afraid your comment that the errors are +-5% is wildly optimistic. I have just plotted the errors from the data in your "Valves-2.xlsx" file, and I enclose the results. The error graph is on a 3rd tab on the Excel spreadsheet - and the data is derived in the Data tab.

As you will see only one tester - your VCM163 gets what I would call "close" to the DC results. Most of the testers are within a +-10% bound with Vg below -25 volts (i.e. -15 to -25V). They mostly look pretty wild as the Vg drops below the -25V point.

I don't know whether all the testers make the -25V point a significant one, where a change of grid voltage range is required. It certainly does on my Mk.IV, and I know there is something dodgy going on around that switching point with my own VCM.


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File Type: pdf Valves-2_Errors.pdf (91.2 KB, 13 views)
File Type: xlsx Valves-2_Errors.xlsx (21.6 KB, 14 views)
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Old 14th Aug 2017, 8:58 am   #73
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Default Re: Free Standardised Valves

And we might usefully debate what level of accuracy is acceptable for a VCM?

For the average user who is just trying to get kit working at all, then I doubt whether accuracy is of any importance at all. All they really need to know is does the valve heater still work, and does it have any emission? The go/no-go test indications are quite good enough for that level of testing.

Those (few) of us who are analysing circuits and trying to understand why an equipment does/does not meet its specification is surely going to want something a lot better than that. A starting point might be to note that most valve circuits have passive components with tolerances of +-10%. Occasionally you get circuits with passives down in the 1 to 2% region, but they are not typical.

That observation suggests to me that valve measurements that are better than the circuit tolerances is what is required. So I would be aiming for +-5% on a VCM, with a worst case of +-10%. Probably most helpful is to know where one's VCM is inaccurate, so that one is forewarned not to rely on its results.

Richard

Last edited by trh01uk; 14th Aug 2017 at 8:59 am. Reason: Missing words
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Old 14th Aug 2017, 9:16 am   #74
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Default Re: Free Standardised Valves

Can we actually say anything about the tolerance since we have all tested different 6AU5GTs?

The 6AU5GT that David sent me has as far as I am aware of only been tested by me and David (correct?).

In a previous post I mentioned that we need to add which valve that has been tested so that we only compare our measurements against the same valve.

I haven't looked much at the measurements I got since the valve was damaged during shipping but a quick check against Davids measurements shows that they are very close.
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Old 14th Aug 2017, 9:42 am   #75
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Default Re: Free Standardised Valves

Martin,

sorry - I used Nick's compiled data without question. I assumed we had all used the same one valve for testing - since the data includes only one base line set of DC test results.

Looks like Nick - and my derived results - are all junk and need totally reworking. I assume all the data is actually on this thread if we go looking for it.



Richard
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Old 14th Aug 2017, 9:54 am   #76
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Default Re: Free Standardised Valves

In our enthusiasm some data from different valves has been combined. I am just in the process of splitting it out and creating an excel spreadsheet and graph for each valve.

I will name these files with the valve type, valve number (as per David's naming) and date of revision.

Then we can keep track of what is going on.

Nick
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Old 14th Aug 2017, 11:29 am   #77
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Default Re: Free Standardised Valves

I have now done revised spreadsheets for 6AU5GT valves numbers 1 through to 5.

I hope I have picked up all posted results for these.

You will see that each file name shows the type of valve, David's applied number and the revision for the spreadsheet (all have been started at RevA).

Having done these five spreadsheets I find it interesting that David's Mk3 compared to his DC tester does not show a constant difference across the valves (these are of course the only tester results that spread across multiple valves apart from mine for valves 1 and 5).

Perhaps someone can enter the KTW61 results on one of these spreadsheets and then resave to create their own spreadsheets? (Unfortunately I have to do some proper work now!)

regards, Nick

6AU5GT Nr One RevA.xlsx

6AU5GT Nr Two RevA.xlsx

6AU5GT Nr Three RevA.xlsx

6AU5GT Nr Four RevA.xlsx

6AU5GT Nr Five RevA.xlsx
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Old 14th Aug 2017, 11:57 am   #78
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Default Re: Free Standardised Valves

And here are the pdf versions.

6AU5GT Nr One RevA.pdf

6AU5GT Nr Two RevA.pdf

6AU5GT Nr Three RevA.pdf

6AU5GT Nr Four RevA.pdf

6AU5GT Nr Five RevA.pdf
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Old 14th Aug 2017, 1:52 pm   #79
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Default Re: Free Standardised Valves

Folks, Me edd is swimming with Hexhell !
Martin - back on the 12th, your tabulations & graphs included Nick's & Richard's results. Yes they were fortunately within 5%, but remember - those guys had a different valve - 6AU5GT No 1,. You & I shared No 3.
Nick - thanks for the pdf versions.
Richard - good point. Would everyone be happy with getting within 5% of my DC Tester/Martin'sRoetest/ & the two 163's - all jolly close. Also remember what I said a few posts back about "Green Zone" readings on meters. I'm sure 5 - 10% of centre green would be acceptable.
Talking of meters - I'd really like some Taylor & Mullard enthusiasts to join in the debate. Their views are just as important as us AVO VCM folk's. Even though accurate Ia's aren't a serious feature with them. Then there are the Sussex enthusiasts - come on guys. Perhaps all this talk of graph analysis is putting some Forum folk off.
As Richard says, some of us, but not the vast majority of valve testing folk, do delve into Static testing(Mu, Barkhausen's Law, etc.) and Dynamic testing ( Gain - both mathematical & visual on a scope). All interesting & whiles away the winter days,( I can modulate the grid with 1KHz).
I've now graphed 6AU5GT No 6 (the last one), and it will return with Mark James after his weekend visit.
I'll just keep flogging on with my metric graph paper, but if there is also a heap of Exel graphs doing the rounds, that's OK with me. But they need to be in the same format Martin & Nick. As long as all this graphing & Gm-ing results in lots of Forum folk understanding their testers & vcm's.

Regards, David
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Old 14th Aug 2017, 2:40 pm   #80
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Default Re: Free Standardised Valves

David,

Just comparing the graphs for 6AU5GT No 1 and No 5 (where you and I have both tested the same valves with the same testers) it occurs to me that whilst my VCM163 follows your DC tester line pretty well on the graph for 6AU5GT No 1 there is a variation between them between grid volts 27 to 30 on the graph for 6AU5GT No 5.

It almost looks like there is a dip from the line of the smooth curve for the DC tester on the graph for 6AU5GT No 5. Is the DC tester without flaws or could something have happened to cause it to give some slightly duff readings in that zone?

regards, Nick
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