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David Simpson · 13th Aug 2017, 10:59 am

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

13th Aug 2017, 10:59 am	#69
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,852	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