Of Blue Glows in 3-500Z Eimac Tubes

[Robert S. Capon]

I appreciate everyone's input on the blue glow from the 3-500 in my SB-1000.
The e-mail was unanimous that it's a common phemonena, and that I shouldn't go
to the expense of replacing the tube until the performance of the amp begins
to fall off.

There were two lines of thought on the cause.  One line was gas in the tube,
the other was phospherescents.  So I called Eimac (now a division of CPI
rather than Varian), and spoke to tech support.  Both causes are correct.  If
the blue glow exists between the glass envelope and the plate amd seems to
move around, it's probably caused by trace amounts of gas.  However, if the
blue glow hugs the glass envelope and is fixed, it's caused by trace amounts
of phospherous that was introduced in the glass washing process.  Of the two
phenomena, the latter is less likely to impact performance, but in any case,
he suggested to run the tube until performance falls off.  My tube falls into
the latter category.

I happen to have a pair of spare tubes, and the SB-1000 only uses a single
tube.  So, I'll continue to run this one, until the performance drops off.
Eimac indicates that the tubes are no longer made, and they're beginning to
get scarce, so better to save them for a rainy day.

I'm getting great signal reports with the amp, which I finished building only
recently.  I was nervous about aligning the amp because of the high voltages
involved, so I sent the amp off to Ron at RTO electronics for aligning, which
is one of the great services offered by RTO in addition to trouble-shooting
rigs (e-mail: rtoxl at andrews.edu).

Anyway, I broke with one call a 20 meter SSB pile-up to 9K2ZZ who was working
simplex on the busy 14,195.  He gave me an S-9 +20 report, and also reported
good audio.  It's really nice to have a big piece of gear in the shack that
says "Heathkit".  Looks VFB.

I also appreciate the e-mail tech support from Ron, Randy, and others on the
Heath list while I was building the unit.

73,

Rob, W3DX

--- --- --- --- --- --- --- --- --- --- --- --- --- --
To subscribe: listserv at listserv.tempe.gov
and in body: subscribe HEATH yourfirstname yourlastname
To unsubscribe:  listserv at listserv.tempe.gov
and in body: signoff HEATH
Archives for HEATH: http://www.tempe.gov/archives
--- --- --- --- --- --- --- --- --- --- --- --- --- --