[Amps] TH347 filament ramping

[Carl]

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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