[R-390] Heat Death

[David Wise]

Issue 6 and JX-21A Issue I are 6AC7.
JX-17 is 6AH6.

Was the JX-17 the only version updated to 6AH6?
Is anyone actually using the FCU today?

Thanks,
Dave Wise

>-----Original Message-----
>From: r-390-bounces at mailman.qth.net 
>[mailto:r-390-bounces at mailman.qth.net] On Behalf Of Les Locklear
>Sent: Monday, December 03, 2012 6:59 PM
>To: Todd, KA1KAQ; R-390-List
>Subject: Re: [R-390] Heat Death
>
>The original tube for the FCU (frequency control unit) was a 
>metal tube, a 
>6AC7, later versions used a 6AH6 7 pin miniature glass tube.
>
>Les
>
>-----Original Message----- 
>From: Todd, KA1KAQ
>Sent: Monday, December 03, 2012 8:08 PM
>To: R-390-List
>Subject: Re: [R-390] Heat Death
>
>On Mon, Dec 3, 2012 at 5:32 PM, Barry <n4buq at knology.net> wrote:
>
>> > Interestingly there is one application where I found the IERC tubes
>> > were a
>> > very bad idea. On the Hammarlund SP-600, any of the JX models that
>> > have the
>> > crystal deck, there is a tube on the backside of that module. It is
>> > sideways mounted. IERC shields make that tube run almost hot enough
>> > to melt
>> > solder (it will definitely melt the skin off of your finger).
>>
>> I would think that's to be expected since the chimney effect 
>of the shield
>> can't work that way.
>>
>
>That's exactly right, and why the later IERC shields with the 
>open/tabbed
>tops work best, and why you don't want to use a short shield 
>on a tall tube.
>
>But I'm a bit confused as to the original post. Wasn't that 
>particular tube
>on the SP-600 crystal module a metal octal based tube anyhow, 
>not a 7 or
>9-pin miniature? Even if IERC shields for that type of tube 
>were available,
>it would seem redundant even in vertical service.
>
>de Todd/'Boomer'  KA1KAQ/4
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