[Elecraft] Help Voltage check KPA100

[James T. "Jim" Rogers]

Jeff wrote:
"I am at the voltage check on page 43 of the KPA100 manual. I only have 0.5
V
on the cathode of D13 instead of 90 to 150 V."

OF IMMEDIATE CONCERN to me is 0v on the Q7 side of R12 indicating that Q7 is
turned on. 5T should not be present on the gate of Q7 except during
TRANSMIT. It is possible Q7 may have been damaged by ESD. The ZVN4424 is
very ESD sensitive.

SECONDARILY I am concerned that only 76V is found at the junction or R11,
R12. Check thoroughly for a solder bridge. It appears something is pulling
the 90-150v power supply down. This is not a high current supply so it won't
take much to pull it down. I would check component orientation in the
90-150v supply area, particularly the diodes.

You may be chasing more than one problem, If you can lift the common sides
of R11, and R12 and check that 90-150v is actually being produced at the
cathode of D1, this may help you in isolating the problem(s) to the TR
switch area.

I might make sure the POWER is at MINIMUM and I would even go so far as to
remove the RF connection between the K2 and the KPA100 and put a dummy load
on the K2 until I was able to verify the operation of the TR switch in the
KPA100 but then again I am the nervous type.

I wish I could be of more help. I am just giving my thoughts from reading
the diagram and do not have near the knowledge base of the "gurus" who all
appear to be at Dayton.

73 Jim, W4ATK
K2/100 #4028