:[snip] Have just finished the re-tube of a "Left for Dead"
:Dentron GLA-1000. Output is fine except on 10 Meters. Instruction manual
:says unit is "modifiable" however this "mod" already appears to have
:done as the inductor is tapped and band switch goes 1 position past 15M
:10???. Does anybody have the "detail" that I obviously have missed!??
:help greatly appreciated.TNX de Steve
I don't have the information handy, but from memory.... The GLA-1000
arrives with the ten meter coil installed, just disabled with a
mechanical stop on the band switch. Part of the mod is to back off the
knob, band switch nut, and re-position the band switch stop to allow the
switch to contact the 28MHz position.
The GLA-1000 didn't have tuned input which was later added with the
GLA-1000B. The tuned input makes a heck of a difference in the amplifier
linearity with solid state rigs. The 1000B ten meter input was a small
green toroid (value unknown for my lack of notes at this location), the
exact same type as the 15 meter toroid, less turns. The input cap(s) were
also much less. Some models of amplifiers I've built just required an L
network.... less the tube side cap of the traditional pi circuit.
I didn't see what power output you received with the new tubes. I also
didn't like the bias value the Popular Svetlana paperwork posted. Real
world, four 6LQ6 tubes should output about 350 to 550 watts, with 40 to
60 watts cw input power. These are good amateur practice rules and
includes the 10 ohm resistors in the cathode lead. Poor amateur practice
means you drive the amp with values over/above 60 to 75 watts and work
all VCRs and "cheezy telephones".
The output of the sweep tube amplifiers does drop off at 28MHz vs the
lower bands, but not really to crazy. Most of the problems I've run into
have been caused by poor tank circuits. wrong values, both in
inductance and physical size (small material diameters).
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