[Yaesu] Running a single sweep tube in the final of an FT-101-B

2003年9月21日 22:38:26 -0400

Greetings list!
I lost a final tube in my FT-101-B and did not have a spare or a pair
back in late 80s or early 90s. I implemented an emergency
reconfiguration that let me get on at about half power and worked 10 or
so countries within a few hours of having gotten the rig back on line. Of
course good cdx, good QTH (1km fm ocean - elevation 75 feet, underground
stream, and being in Eastern MA, plus using Hustler 5-BTV vertical with
its low angle so an S-5 or S-1 sig gets places a dipole won't get, ground
or coil loss and missing tube notwithstanding. 
Anybody else ever run a single sweep tube in the final of an FT-101?
Recognizing my plate impedance would rise and the match to the tank would
at least require retune and neutralization would need trim, I ventured to
try this approximate method to revitalize the rig at low power. I
studied the 101-B schematic, saw the 12 volt to seriesed final tube
heaters and that there was an external power plug socket with a jumper
plug in it. I removed the short on the power jumper plug, jumped the
heater pins on the base of the bad final tube, and connected a 6.3 AC
transformer externally to the heater buss and ground at the jumper plug. 
I probably should have bypassed the xfrmr pri & sec but did not. 
Fired up and neutralized the xmtr immediately then got on the air to try
out the mod and evaluate any feedback from the world. The final draw was
about half current maybe, a bit more on some bands. I was able to
resonate the tank and peak output on all bands. Reports did not
criticize and I invited such, to be safer than just trusting to all the
discriminating ears out there. Until I got a new pair of finals I spent
some considerable and good times on the air but at ~ half power. 
Just curious: to what lengths might others have gone, and what might I
have inadvertently caused doing so. BTW I believe I left the tube plate
lead dangling and removed glass envelope and elements of the tube rather
than leave the passive interelectrode capacitance and stray capacitance
and element inductances so it had to be re-neutralized. 
Enjoy seeing the lore on the Yaesu line and rare remarks about the old
fox tango news letter and misc mods and gripes on the old radios! mine is
still backup/ odd time s can get on from my summer place when I have not
brought my FT-990. I have yet to get inside the 990 and do any of the
corrective or maintenance actions. Hoping to get my memories going again
assuming a new memory battery will do the trick
Enjoy each radio for its relatively highly accurate frequencies when
calibrated to prescribed methods. Remembering the BC-221 surplus freq
meters of WWII,
I was impressed at how well I knew my frequency on the FT-101-B as Nobody
complained on WW SB or ARRL SB when I worked 40 or 80 meters split
frequencies in DX contests always felt like cheating to be aware of a
quiet place to call and it seemed so easy to get in and out, working the
DX run 
stations, particularly those who were not causing pile ups!
Think I 'll crawl back in my hole posing one question.
On the FT-990 main dial is there any adjustment of slop or wobble? If not
is the dial mechanism a spare part needing replacement. Consultation of
the manual and some disassembly will show me the way but possibly a few
words will help me focus on issues I barely realize exist. 
The FT-990 seems to work well once powered up and SWR knocked out on the
bands; leaving power up on the rig over a whole contest is necessary,
considering no functional tuner or frequency memory after power down
until battery is replaced.
Think I will crawl back into my hole and revert to vicarious groundhog
mode!
73 and DX or awards/ contest points and much FUN.
See you on 'tests or maybe a rag chew.
Thanks for being more terse than I.
Dennis N1DS
________________________________________________________________
The best thing to hit the internet in years - Juno SpeedBand!
Surf the web up to FIVE TIMES FASTER!
Only 14ドル.95/ month - visit www.juno.com to sign up today!