OFF TOPIC, SORT OF

[Paul Blumhardt]

You can check for grid to cathode/filament shorts with an ohm meter.

You can also check for control grid-screen-suppressor grid shorts 

Finally, most high power tubes have two grid pins - you can check for open
grid connections too. Don't forget you can check for open filament/cathodes
too.

3-500z, 572B and 811 are very common, so it should be easy to find a buddy
with an amp with those tubes to test your tube in. Even the 3CX1200/1500
amps are pretty common these days.

Paul

-----Original Message-----
From: Heathkit Owners and Collectors List [mailto:HEATH at LISTSERV.TEMPE.GOV]
On Behalf Of Bob Groh WA2CKY
Sent: Monday, October 08, 2007 12:13 AM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: OFF TOPIC, SORT OF

Oh, boy. Just went through this on the AMPS list. I had a 4-1000A and asked
the same question. I think the full answer is that the only valid way is to
fire it up under voltage. Best to run RF to it but a check of idling current
may be sufficient. For an older tube, you need to (or should at any rate)
condition the  tube for a couple of days (run filament voltage alone) and
then put HV on it and run it longer. You need to check emissions after you
have conditioned it and that means checking idling current which means full
HV on it. Someplace I've got information on all of this. 

I had a beautiful 4-1000A in pristine shape. Sold it subject to return if it
didn't work. Buyer put it in his PA, conditioned it and then tried it. No go
- no idle current. So the tube was returned to me and I refunded buyer's
money. 

At least that is my take on it at this time. I'm stopped for a bit until I
get the old KW fixed so I can run the tests myself. Some of the guy's have
built HV testers and they firmly believe that you need to HiPot all vacuum
parts before using. 

So it doesn't look there is any easy way to do this without a full blown RF
deck or test bed.  Ugh.

73
Bob, WA2CKY


----- Original Message ----
From: Murray Grandy <mgrandy at TELUS.NET>
To: HEATH at LISTSERV.TEMPE.GOV
Sent: Sunday, October 7, 2007 1:54:31 AM
Subject: [HEATH-TEMPE] OFF TOPIC, SORT OF

DOES ANYONE KNOW OF A WAY OF TESTING TRANSMITTER TUBES SUCH AS 4-400. WAS
THERE EVER ANYTHING IN ANY OF THE ARRL HANDBOOKS. SEEMS LIKE THERE MUST BE
SOME WAY TO JERRY RIG SOMETHING THAT WOULD DO A BASIC KINDA TEST.
Murray

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