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Old 23rd May 2024, 11:31 am   #1681
Craig Sawyers
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Default Re: The "Sussex" Homebrew Valve Tester.

Quote:
Originally Posted by Ed_Dinning View Post
Hi Folks, just to reiterate David's comments.
I have wound over a 100 transformers for the Sussex and people have made up their own transformer "collections"
I have had 1 of my transformers fail and I have been asked about damaged testers by a few people. In all cases this has been due to the use of the tester to "burn in" power valves.
Very few testers are designed for this. I state a duty cycle of 30% for my transformer
This keeps both the size and cost of the transformer down and reduces stress on the power supplies in the tester itself.

I have built special testing transformers to specifically "burn in" valves; these are larger and more expensive. They do not need the sophistication of the Sussex to operate.
Test on Sessex first; run for as long as needed on specific, simplified burn in rig; retest on Sussex to compare.

Ed
As Ed knows, I'm getting my soldering iron ready to build a comprehensive kit of Sussex bits I bought from a list member.

But the inadvisability of using a valve tester for burn in duties is a good one.

Now Tektronix used to burn their valves in before installation in an oscilloscope. These were specialist racks with a serious power supply rated for the purpose. The had the ability to turn the valves on and off on a defined cycle.

If anyone is interested in this the data on the Tektronix burn in programme for different valve types is here https://w140.com/tekwiki/wiki/Reference_material

Specifically

https://w140.com/tekwiki/images/0/0a/Tek_tube_aging.pdf

Racks contained the specified numbers of valves - 50 typically - with a chunky heater transformer capable of 15-20A continuous. HT was simply rectified and smoothed 117V mains.

But try that with a valve tester, even with a single power valve, and wait for the smoke to get out.

Craig
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Old 23rd May 2024, 12:05 pm   #1682
Craig Sawyers
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Default Re: The "Sussex" Homebrew Valve Tester.

Because I'm a bit retentive, I searched a VCM163 manual I downloaded an eternity ago from somewhere (perhaps BAMA) for the number of entries for the socket types which were on the MkIII tester - which along with the MkIV had the most comprehensive range of sockets.

There are 5833 entries in the VCM163 manual entries for MkIII valve sockets, with the numbers of entries and percentage of the total:

B9G 55, 0.9%
AO8 1163, 20%
B7 530, 9%
SM5 11, 0.2%
UX6 123, 2%
UX4, 277, 4.7%
SM4 31, 0.5%
UX7 34, 0.6%
SM7 15, 0.25%
UX5 93, 1.6%
B3G 34, 0.6%
MO8 65, 1.1%
B8A 197, 1.1%
B7G 903, 15%
8SC 308, 6%
B8G 14, 0.25%
B9 26, 0.4%
B4/5 678, 11.6%
B9A 1186, 20%

So fitting B9A, B7G, B4/5 and AO8 (AKA IO8) covers a total of 3930 valve types or 67%of the total.

Then add others to cover the valve types in your hoard...

Other valves in the VCM163 list that are not relevant to a 9-pin tester are 198 entries for 12-pin Compactrons.

Others of interest are Nuvistors (13 entries), but they are testable with an adaptor, and most of the small number of B10B based valves for which most only need 9 connections, and already have equivalent listings.

I'll get back under my chair....

Craig
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