Hello again,
:I have a Kenwood TL911 Amplifier which is in good condition except for
the
:output tubes.
Never knew Kenwood made the amp... Sounds like another classic sweep tube
amp, just this one has five tubes.
:The tubes are TV sweep types 6JE6C. The ARRL handbook rates these tubes
at
:30 watts DC power dissipation at a plate voltage of 500V.
If my memory serves, they actually have about 33 watts diss per tube,
some brands had better construction practices. They rated Vp was rarely
used. These sweep tube amps were often abusive to the tube as they were
once common and cheap.
I pulled many out of the backs of tube TV's.
:The tubes are run
:in this "linear" with a plate voltage of 1300V (5 tubes in parallel.)
and
:the amp's rated input power is allegedly 2.0 KW PEP(user's manual).
Wow, that's even spanking them worse than the dentron GLA-1000 does. Your
really pushing it with that high a plate voltage. Even though the Dentron
used about 1100 to 1200 volts, it always scared me even though I've never
had one flash over.
The realistic operation of the 6LQ6 type sweep tube is 600 to 900 volts,
grounded grid and some resistors in the cathode leads. 10 ohms will help
with the linearity.
2kw .... on a good day with a tail wind.... I don't think so.
If you really want a realistic type of operation. My current 4 tube sweep
amps are as follows:
4-6KD6 tubes and 900 Vp grounded grid operation. Driven with 40 watts cw
carrier, they deliver around 400 watts carrier output and a relative
clean signal on the analyzer. In SSB service, they "can" be driven with
up to 100 watts for 475 to about 600 out... hardly worth the trouble.
Every test I've ever done shows they really get non-linear, starting
about 65 to 70 watts and drive above 80 watts gets you on the way to a
"worked all vcrs" award with some low Q tanks. The tubes will have a much
shortened life if the duty cycle in SSB levels is increased with audio
processors. The rarely have tuned input circuits as they were made to be
driven with tube final HF rigs.
The dentron 4-6LQ6 drives with 40 to 60 watts clean and puts out about
350 to 550 clean. There are power levels above 60 watts which work, but
you don't want to go there with a quad tube amplifier.
Depending on your circuit, the five tube amp should drive with 50-75
watts for clean output, add the 10 ohm resistors in the cathode leads and
you can up that a bit with better results. The Svetlana EL-509 is the
way to go unless you can buy some NOS tubes priced two days ago at $43
+s&h
Another though would be the rebuild of the amp with 811A's as they are so
cheap from china. Prob wouldn't be that practical though. The EL-509 is
almost a direct swap and mod tube.
:These tubes are hard to come by and expensive in relation to the worth
of the
:amplifier. I have some 6146 tubes which have a recommended maximum plate
:voltage of 800V i.e supposedly 300V higher than the 6JE6 and a rated DC
:power dissipation of 25 watts. My question is, can I substitute the
6JE6s
:with the 6146s ?.
Yeah, but it's not practical. One reason is the VHF gain of the 6146
Another is the high C values of the typical sweep tube would require a
rework of the tank values.
Not to mention the lower Plate diss.
: If this is a No No are there any suggestions for an alternative
substition
:(could be less than 5 tubes). Only looking for about 400W PEP output.
:Supplies available are as follows.
:Plate Voltage: 1300V Plate Current: 1.5A max.
:Screen Voltage: 70V (but could probably squeeze about 170V out of the
:existing supply).
:Bias Voltage: Variable down to -75V
:Heater Voltage 6.3V Heater Current 12.5 Amps.
the el-509, 811A, 6KD6, 6LF6, 8950 or anything you can get your hands
on cheep.
:Any advice would be appreciated.
Buy Microsoft at $12 a share.... (just kidding)
:Eric
:ZS5EWM
See the above Eric. The EL-509 or NOS tubes are your best bet. My first
choice is the EL-509
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