[Johnson] Slightly off topic question concerning mercury vapor rectifiers

[Roy Morgan]

At 04:50 AM 10/25/02 -0700, Joe Yamond wrote:
>   Luckily I
>didnt take out the transformer, probably only the
>tubes. I do love that cool blue glow but if I get
>tired of it I may swap for SS repl.


Joe,

Be warned.  That lovely blue glow is habit forming.

AND.. when the glow flickers in response to your keying or voice, you can 
get really attached to it. In my experience there is only one feasible 
response to this difficult addiction.  It involves all of the following:

1) Buy all examples of these tubes you find at hamfests and the 
like.  Cultivate the habit of digging way down in boxes of loose tubes to 
find any lurking there.. Memorize the shape and appearance of the 
lowly-looking 816 so you don't miss any of them.  Further expertise in this 
area will let you spot and recognize old and odd tubes of this sort like 
the 866 (non-A), even the globe variety from the 1920's and 30's, and one 
or two tubes similar to the 866 not made since the late 1930's.  More 
modern Phillips versions of the 866A have a thin, almost tubular shape and 
may escape recognition by less well informed addicts.

Develop a negotiating strategy that goes something like this:
   "Hey, this tube looks all cruddy inside, do you know what it is?"  (Of 
course, YOU know what it is.. it's an 816 with yukky-looking mercury all 
over the insides!)
   "Gee, it looks all burned out, what do you asking for these, anyway?"
   "Well, the guy over there sells tubes this size for two bucks each.."

2) Make up a little board with a filament transformer and two sockets so 
you can heat up the spare tubes from time to time and keep them happy.  If 
you are really dedicated, you can lash up a second filament transformer and 
resistor load to run just enough current  through them to get the blue 
glow.. (include a separate switch, for turning on after enough warm up 
time.)  Make sure your operating tubes are fully warmed up before you apply 
high voltage. Do not be in a hurry to get on the air until the tubes are 
happily warmed up.

3) In the case of the Johnson Valiant, arrange a mirror so you can see the 
tubes clearly while operating.  Eventually, you may own a transmitter that 
has solid front panels and does not let you see the tubes.  (The TMC 
GPT-750 is of this sort.)  I am investigating the use of  tiny video 
cameras to bring the images of the rectifiers and the finals out so they 
can be seen and properly appreciated.  Home brewed equipment, of course, 
should be built with proper windows in the panels.

Only some of this is tongue in cheek. This addiction is serious.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --