OFF TOPIC, SORT OF

[Bob W5UQ]

Bob, 
       you have said it all and that's about it. 

I've had broadcast transmitters that I bought used tubes for, had spares 
laying around and wondered the quality of them.  We could check the 
filaments, check for shorts...in fact I've zapped some big final tubes 
with AC volts (on a variac) to clear the shorts....and some really 
worked too.

_BUT the only way we could tell how well they worked,  was to put them 
in service.
_
Looks didn't really mean a thing....  terrible looking tubes may work 
great and new looking tube may not work at all.

HOWEVER, sometimes you can take a sweep tube (glass envelope) and look 
inside the tube, follow the cathode lead up to the cathode and see that 
it's "blown open".  I have a sweep tube, 6JE6C/6LQ6 tube that you can 
see the cathode lead is burned in two.   Otherwise the tube looks great.

Bob W5UQ  Tampa

Bob Groh WA2CKY wrote:
> 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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