[AMRadio] fs/ft: Eimac 4CX250B - Unknown Condition

Brett Gazdzinski brett.gazdzinski at verizon.net
Thu Nov 29 09:37:30 EST 2007

I avoid 4cx250  pull outs as they are almost always bad.
They may test fine, but they arc over after a while in use.
I have about 30 of them that do that.

As they are used, the stuff they made to coat the cathode
(so it emits electrons) gets deposited all over inside the tube,
and at some point they start arcing over.
It just seems to come down to run time (filiments on).

They tend to work for a while, then arc, and the more
you use them the more they arc, till next time when you
start over again, each time getting shorter before they arc.

Maybe reducing the voltage to say 1000 volts
(down from 2000) might give them more time.

I consider these tubes worthless unless they were not used
or have low hours on them.

Not sure what new ones go for, I got 4 new ones a few years ago
for $160.00, used ones used to be $5.00 and not usualy worth that.


----- Original Message ----- 
From: "Rev. Robert P. Chrysafis" <kc8gpd at hotmail.com>
To: <AMRadio at mailman.qth.net>
Sent: Thursday, November 29, 2007 9:25 AM
Subject: [AMRadio] fs/ft: Eimac 4CX250B - Unknown Condition

> I got this from a radio station in a lot of stuff and it has been floating
> around my house for quite some time. I have no use for it as i'm into QRP.
> have no idea if it works or not. It looks like it's in good condition.
> I'll swap it for an interesting technical trinket or best cash offer plus
> shipping.
> My interests are Part 15 AM Microcasting and Computers.
> Thank You,
> Rev. Robert P. Chrysafis
> Universal Life Ministries
> http://www.ulc.org
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