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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 16th Oct 2017, 4:53 pm   #141
David Simpson
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Default Re: Free Standardised Valves

Well Chris,
Wow - what a difference a few weeks have made to this valve's O/P !
I chickened out at -18V Vg with both my testers, but even then without the ferrited adaptor - it still rose to 100mA.
That golden "X" plot at 100mA I'm sure is parasitics. Likewise I suspect that your DC tests might also be parasitics between -17V & -15V. Certainly, my tests today & your DC test are way above those taken a few weeks ago by us & others.

Regards, David
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Name:	Testing Chris's valve (a).jpg
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Name:	Testing Chris's valve (b).jpg
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Name:	Testing Chris's valve (c).jpg
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File Type: pdf Chris's Graph (a).pdf (342.3 KB, 20 views)
File Type: pdf Chris's Graph (b).pdf (260.2 KB, 11 views)
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Old 16th Oct 2017, 5:40 pm   #142
chriswood1900
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Default Re: Free Standardised Valves

David
Thank you for the confirmation on the results, when it first happened it left me confused. It also seems that your latest figures are even higher than I was getting, perhaps we've found a new way of upping the performance of valves, just keep posting them! Wait for the valve audio fans cotton on to this.
Regards
Chris
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Old 16th Oct 2017, 8:43 pm   #143
David Simpson
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Default Re: Free Standardised Valves

The original 5 plots all start out within 10mA of each other, then squeeze to within 5mA of each other at -20V Vg, then peak within 10mA of each other.
If Vh, Va & Vs are the same for all 9 plots - then only the grid can be responsible for excessive Ia for the last 4 tests. It passed all my Mk3's inter-electrode insulation tests & no doubt the same AVO tests on the CT160 & 163. Possibly there has been some sagging of the grid's coil, thus giving less control of the electron flow. Hence susceptibility to parasitics approaching 100mA. Probably caused by postal damage or being manhandled around all our workshops. Note that Martin in Sweden also had possible postage damage to electrodes with valve no3. No reports of a similar phenomenon have come back from folk using the 6AQ5's or KTW61's,thankfully.
Still no interest or reports from Taylor, Mullard or Hickok owners. A pity. Their involvement is just as important as those of us with AVO's, Sussex, DC Testers, Roe Testers, etc.

Regards, David
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Old 7th Nov 2017, 5:04 pm   #144
chriswood1900
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Default Re: Free Standardised Valves

After 3 very busy a weeks I found some time today to test Martinís valve no 72 on my CT 160,l which if you remember the fun with Valve 5 was an interesting exercise. Valve 72 is still 6AU5 but of earlier RCA manufacture not GE and as you will see in the attached results produced higher Ia results at grid voltages around -30V. but very similar at the lower end -15V. The results between Davidís results and mine were so similar I thought there must be a mistake but on double checking proved correct. see post #130
Regards
Chris
Attached Files
File Type: pdf Martin's 6AU5GT Nr 72 V1.pdf (31.9 KB, 10 views)
File Type: pdf Martin's 6AU5GT Nr 72 V1 Data.pdf (28.4 KB, 8 views)
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Old 7th Nov 2017, 5:45 pm   #145
Mark James
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Default Re: Free Standardised Valves

I still have two 6AU5GT's for collection at Goldborne on Sunday or at next RWB. PM me if you would like one.

Mark
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Old 7th Nov 2017, 8:30 pm   #146
David Simpson
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Default Re: Free Standardised Valves

Well done Chris,
Looks like my testers & your CT160 just about match Martin's RoeTest result for 250V/150V/6.3V. So a good result for the three of us.
Hopefully folk will grab the two valves which Mark is taking to Goldborne & join in this thread. Also folks, don't forget - I still have more of Martin's st'd 6AU5GT's which he'd kindly sent over.
I'll reiterate, this isn't a competition between different makes of valve testers or VCM's, or between different Forum folk. Perhaps Martin,myself,Chris, and one or two others have acquired close results, but that's because we're keen valvies & have spent hours working on our valve testing gear. Our aim is to help & advise others, whilst offering trusted free standardised valves to pass amongst the vintage fraternity who own testers.

Regards, David
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Old 8th Nov 2017, 3:12 am   #147
Dekatron
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Default Re: Free Standardised Valves

Nice to see that the curves agree so well.

Some comments on the vales I sent to David below.

All of the 6AU5GT's I sent to David came from HP and/or Tektronix instruments that had been scrapped after being used as donors for other instruments, so they had all seen some use but were working well enough to be saved as spares.

They were all tested a few times each and had warm-up times varying from 5-15 minutes with all voltages applied before the measurements were taken, this due to how the Roetest works in automatic mode but also so that I could observe the anode and grid currents during warmup and eliminate any poor valve.
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