[Johnson] FW: Pacemaker

[Glen Zook]

Be very careful using the 6146B/8298A in the Pacemaker.  The rig was designed for the 6146 or 6146A/8298 and the 6146B/8298A is really a different tube and many of the older transmitters designed for the earlier versions are pretty unhappy with the later version.  Any 6146W with a code date of after mid-1964 is going to be the same as the 6146B/8298A.

Although certain particular examples of any of the older transmitter models work fine with the 6146B/8298A most do not.  When using the later version the tubes often "take off", cannot be properly neutralized, etc.

For the article on the 6146 family of tubes that was published in Electric Radio Magazine a while back go to

http://k9sth.com/uploads/The_6146_Family_of_Tubes_1.pdf

The cautions and so forth are in the article.

Glen, K9STH

Website:  http://k9sth.com


--- On Mon, 1/19/09, Langston, Mike <MLangston at pricegregory.com> wrote:

> From: Langston, Mike <MLangston at pricegregory.com>
> Subject: [Johnson] FW: Pacemaker
> To: johnson at mailman.qth.net
> Date: Monday, January 19, 2009, 4:02 PM
> I have started the alignment sequence in the manual. VFO
> alignment
> (tracking) proceeded with no problems. Next section is xtal
> osc. Time
> out while I built an RF probe. Turned the rig on it's
> side and turned it
> on to let it warm up (standby position). 3-5 minutes later
> a slight
> buzzing sound and the 5A fuse let go (one in the xfrmr
> primary - got rid
> of the fused plug). Replaced with 5A slo-blo and watched
> closely this
> time when I turned it on. Same time delay and started
> hearing the buzz.
> The 6146 final looked like it was on fire inside with a
> pulse that
> matched the buzz frequency. Turned it off.
> 
>  
> 
> Tested the 6146. Filament lights but reading is 2000 on my
> Stark 999.
> Minimum good reading is advertised as 4100. A new 6146B
> tests 4500-6000
> (I've got a bunch of them). This same tube tested good
> when I first
> checked it.
> 
>  
> 
> Could having the rig on its side have caused something to
> sag and short
> inside the tube? I've had finals self-oscillate before
> (HT-44) but there
> was no associated light show. I don't really want to
> ruin a 6146B just
> to satisfy myself that there was nothing wrong with the
> original tube. 
> 
>  
> 
> Any ideas?
> 
>  
> 
> Thanks in advance.
> 
> Mike KL7CD
> 
> Johnson mailing list
> Home: http://mailman.qth.net/mailman/listinfo/johnson
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Johnson at mailman.qth.net