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


Brett Gazdzinski brett.gazdzinski at verizon.net
Thu Nov 29 09:50:16 EST 2007


The tube may be fine, but unles you KNOW that, its likely not.
I guess lots of these were used in broadcast service, and when
they started arcing over, they were pulled and thrown in a box
for sale at the hamfest.

I know I bought a lot of them at fests for very little, and 99%
wont work more than a few transmissions before arcing.
The new ones have been in for years without problems...

I was getting 3cx800's as pullouts and 80% of them were useless also.

Brett
N2DTS

----- Original Message ----- 
From: "Rev. Robert P. Chrysafis" <kc8gpd at hotmail.com>
To: "Brett Gazdzinski" <brett.gazdzinski at verizon.net>; "Discussion of AM
Radio in the Amateur Service" <amradio at mailman.qth.net>
Sent: Thursday, November 29, 2007 9:42 AM
Subject: Re: [AMRadio] fs/ft: Eimac 4CX250B - Unknown Condition


> Ok,
>
> I don't know much about this high power stuff. highest power tube tranny i
> have is 36 Watts on the AM BCB for carrier current use.
>
> and actually that is the only tube tx i have. it's going to be a learning
> experience to get it going again.
>
> ----- Original Message ----- 
> From: "Brett Gazdzinski" <brett.gazdzinski at verizon.net>
> To: "Discussion of AM Radio in the Amateur Service"
> <amradio at mailman.qth.net>
> Sent: Thursday, November 29, 2007 9:37 AM
> Subject: Re: [AMRadio] fs/ft: Eimac 4CX250B - Unknown Condition
>
>
> >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.
> >
> > Brett
> > N2DTS
> >
> >
> >
> >
> > ----- 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.
> > I
> >> 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
> >>
> >> Moderator Hunterdonfree
> >> http://groups.yahoo.com/group/hunterdonfree
> >> Moderator NeighborhoodInformer NJ/PA
> >> http://groups.yahoo.com/group/NeighborhoodInformerNewJersey
> >> http://groups.yahoo.com/group/NeighborhoodInformerpennsylvania
> >>
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