[Amps] TH347 filament ramping

[TexasRF at aol.com]

Carl, that was a price quoted by Freeland Products, a tube rebuilder in the 
 New Orleans LA area. New tubes were around $6K from Richardson Electronics 
the  last time I checked. There will be no new TH347 tubes in my future!
 
I have seen pulls for around $200 in Europe but they typically will run a  
maximum of 1.2A plate current where a good tube will run 1.9 to 2 A. Even at 
 1.2A they will output 1500W or more so a pull my be ok depending on what 
you are  looking for.
 
A recent batch of four pulls yielded one tube that did 2000W out, one that  
did 1500W out, one that did 900W out and one that arced and sparked, not  
recoverable.
 
At this rate, a good pull is worth $400 to $800 depending on how good it  
is.
 
I have, as suggested, considered running the tube with low filament voltage 
 when off. My operating style may keep me away from 1296MHz for several 
weeks at  a time so I am not sure I would get a benefit from the low voltage.
 
Too many bands, not enough time!
 
73,
Gerald K5GW
 
 
 
 
In a message dated 8/28/2009 4:53:45 P.M. Central Daylight Time,  
km1h at jeremy.mv.com writes:

Gerald,  have you considered running the filament black when not in use as  
suggested by Siemens?

Is that $2500 in Germany or the  USA?

And what is the going price for a decent one in Europe? My #2 son  just got 
confirmation of his Germany assignment  today.

Carl
KM1H


----- Original Message ----- 
From:  <TexasRF at aol.com>
To: <jtml at vla.com>;  <amps at contesting.com>
Sent: Friday, August 28, 2009 5:33  PM
Subject: Re: [Amps] TH347 filament ramping


> Fortunately  one was used and the other was a rebuilt tube. The filament
> went open  like a bad light bulb when they failed.
>
> The price of rebuilt  tubes has doubled over the past few years. They were
> around $1200 with  a discount coupon now about $2500. While this sounds 
> like
>  a  very high price, the tube is very capable of 3KW plus at 1296 MHz. If 
 
> the
> filament issue is resolved, one can expect a lifetime of  use at amateur
> power  levels. This makes the $2500 price a bit  more acceptable.
>
> So far so good with the relay scheme. That  has been in use for a couple 
of
> years now.
>
> 73,
>  Gerald K5GW
>
>
>
>
> In a message dated  8/28/2009 4:04:14 P.M. Central Daylight Time,
> jtml at losalamos.com  writes:
>
> Gerald,  that's unfortunate, I hope you didn't  pay list price for those
> tubes and  have them fail like  that.
> Your relay scheme seems like it would have  prevented  problems. Did the
> filaments burn out or did they just short to   grid and stick there?
> 73
> John
>  K5PRO
>
>> I lost a couple of  good TH347 tubes due excess  filament current at turn
> on.
>>  I  thought there  was sufficient turn on current limiting but apparently
>
>>  not.
>>
>
> ----
>> 73,
>> Gerald   K5GW
>
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