Most of the use 4CX250 style of tubes available now came from FM base
station or repeater duty. They are usually replaced when the customer
complains and are well cooked at that point.
Even ones that show good output are prone to secondary screen emission and
are poor choices for SSB or modulators.
There are also loads of military tubes floating around and if they look good
and not severly overheated, the chances are that they are still good.
I have about 25 150/250's here that have all passed 125W output muster on 6M
as finals in a Clegg Zeus. Most have been $5 or less (many were freebies) so
there are no complaints. Ive also thrown out several others.
Carl
KM1H
----- Original Message -----
From: "Brett Gazdzinski" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio in the Amateur Service"
<amradio@mailman.qth.net>
Sent: Thursday, November 29, 2007 9:50 AM
Subject: Re: [AMRadio] fs/ft: Eimac 4CX250B - Unknown Condition
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" <[EMAIL PROTECTED]>
To: "Brett Gazdzinski" <[EMAIL PROTECTED]>; "Discussion of AM
Radio in the Amateur Service" <amradio@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" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio in the Amateur Service"
<amradio@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" <[EMAIL PROTECTED]>
> To: <AMRadio@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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