[ARC5] [MRCG] Attic Archaeology

[Scott Robinson]

Hi Jay,

What I do for them is to heat the cathode (6.3V to the heater) and apply 
50V DC between cathode and heater, in both polarities. I measure the DC 
current and it needs to be less than 5 uA, in either direction. I don't 
do this in a tester, but on the bench with two power supplies.

I think a design that uses undocumented properties of a tube or other 
component is silly, but apparently that's how Colossus is designed. 
About half of the 807s I've seen have passed that tests, and they 
clearly separate into two groups with very few on the edge.

I of course also test them with a Hickok 605A transconductance tester in 
the usual way. Your TV-7 has the same measuring engine as a Hickok 
tester, so it will be fine for transconductance testing.

Peace,

Scott



On 4/20/15 6:16 PM, Jay Coward wrote:
> ,
>   What exactly is the H-K test? I have two TA-12  transmitters with I
> think 4 ea 807's. If I can do this test with a TV-7 tube tester I could
> save you the trouble of the test and maybe cull a few out. I only need
> tubes for one. the other is a parter or a project for someone else.
>   Jay
> -----Original Message-----
> From: Scott Robinson <spr at earthlink.net>
> To: Jim Falls <radio-tuber at att.net>; MRCG <mrcg at mailman.qth.net>; ARC-5
> <arc5 at mailman.qth.net>
> Sent: Sun, Apr 19, 2015 9:03 pm
> Subject: Re: [MRCG] [ARC5] Attic Archaeology
>
> Folks,
>
> I'd like to make a plea here. The Colossus computer in the UK  (which
>
> runs and is demonstrated regularly), which was used to decode the German
>
> high command code during WWII, uses a number of 807s (50, I think). For
>
> reasons of preserving all details of the original design, they won't use
>
> 1625s. Don't ask, I already had that argument when I was there and they
>
> weren't willing to budge on this point
>
> I sent them about 30 such tubes last
> year, and they were very grateful.
> If anyone has good (doesn't have to be new)
> 807s, I would like to get
> them, do the special H-K leakage test that Colossus
> requires, and ship
> the ones that pass off to the UK. I will return all that
> fail the H-K
> test to the original owner. In my experience so far, about half
> of
> otherwise perfectly good 807s pass this
> test.
>
> See
>
> <http://www.tnmoc.org/>
>
> for info about the museum,
> and
>
> <http://www.tnmoc.org/explore/colossus-gallery>
>
> for Colossus-specific
> stuff.
>
> It's a really good cause, and if any of you are in the London,
> Bletchley
> Park, where Colossus and other such things are located, is a 45
> minute
> commuter train ride out of (as I recall) London's Euston station. The
>
> entrance to the park is about 1000 feet from the train
> station.
>
> Peace,
>
> Scotty Robinson
>
> On 4/18/15 1:50 PM, Jim Falls wrote:
>>
> I have 18 NIB 1625's and 3 loose that test excellent/near max scale on my Hickok
> 600. Anyone need some? I'll bring them to SLO.
>>
>> At least a dozen nib 211's
> also.
>>
>> More later as I progress.
>>
>> Cheers!
>> Jim K6FWT
>> CBLA #37
>>
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