Re: LF: W1VD amp help

[Rolf Torvik <la2xpa@gmail.com>]

Paul,

also had problems with the W1VD driver circuit (MF version).

The solution for me was to earth all the unused pins of the 74F74.

I can send you the input levels later if needed (not available now)

73 Rolf LA2XPA

2018-04-08 2:09 GMT+02:00 N1BUG <paul@n1bug.com>:

It seems I'm in over my head again. I'm having difficulty getting my
newly built W1VD kW 137 amp to run correctly. I think the problem
may be with my driver board.

Question 1:
Could anyone with a known good W1VD kW deck send me a scope plot of
your gate waveform please?


Question 2:
Using the driver circuit exactly as shown here

http://w1vd.com/137-500-KWRev3.0.pdf

what have you successfully driven it with? Please specify sine or
square wave and drive level.



Here are the problems I'm having:

Using the configuration shown in the pdf schematic above my amp will
not drive with either sine or square wave input at any level up to
+23 dBm from a HP 3325B at X2 frequency (275 kHz).

When I add this X2 multiplier

http://w1vd.com/X2LinearClassDinterface2.pdf

between the 3325B and the amp, it works. Sort of. I changed the
3325B to 137.5 kHz of course. I get about 65W with 13V on the drains
and 250W at 25V. But, something goes into oscillation when RF drive
is removed! Not the FETs. It's either the driver board or the
multiplier or the combination of the two. I can see it oscillating
when I probe the input to the driver board. Oscillation starts only
after RF drive has been present and then removed. Neither the
multiplier nor the driver board show evidence of oscillation when
not connected to each other.

I may have additional issues at high power but I think I should get
the driver working correctly before proceeding further.

73,
Paul N1BUG

--

Rolf Torvik (LA2XPA)
Langveien 61
6510 Kristiansund
Norway
+47 91663050