[Milsurplus] Testing 1625s

[DeWitt Clay]

Not exactly. It would happen so fast that usually I wouldn't see any flash over. The cathode connection would open up acting like a fuse. I am referring to the thin metal ribbon that connects the actual cathode structure to the dumet cathode lead wire coming thru the stem press. Sometimes however, a flash over and arc would start at the upper mica spacer between the anode plate and beam forming plates and/or the cathode. Then some real fireworks would get going. 

In my DX-100 it was always the "back" 1625 that would go with out some cap across either the mod xfmr primary or secondary. Suggest .005 uF, .01 uF, or heatkit's original .02 uF value. I've been using .01 UF in a couple of DX-100 FB.
73, DeWitt  N4QNX


________________________________
From: Bry Carling <bcarling at cfl.rr.com>
To: Ray Fantini <RAFANTINI at salisbury.edu>; DeWitt Clay <n4qnx at yahoo.com>
Cc: milsurplus <milsurplus at mailman.qth.net>
Sent: Friday, October 7, 2011 5:31 AM
Subject: Re: [Milsurplus] Testing 1625s


Interesting - when you say that they got "taken out" - was that an arc-over that destroyed the tube(s) ?

73, de AF4K, Bry

On 6 Oct 2011 at 16:38, DeWitt Clay wrote:

> I have found a Heathkit DX-100 transmitter modulator section a good
> place
> to test a box of unknown 1625 tubes. Various problems will show up
> quickly
> in tubes that can't stand high voltage in the range of 700 volts. I
> also
> made an adaptor to test 1625 and 837 tubes in Collins 32V
> transmitters.
> Recommend all DX-100s to require a (.01uF) cap across the mod xfmr
> secondary or
> surges will take out one of the 1625s. 
> 73, DeWitt  N4QNX