[1000mp] MK5 cw transmit lockup on 40 & 80m

[Paul Ash]

Hello All,

I am experiencing a somewhat strange problem=20
with my MK5. For contesting, I use my PC to key
the rig in CW mode. What I am finding is
when running on 40 or 80m (with 500W or more
out of my Henry 3K) the transmitter will lock=20
"keyed" as soon as I attempt to send any characters.
I have to pull the key jack plug from the front of the rig
to get the MK5 to switch back to RX. This problem is
certainly frequency dependent, no problems at all above 40m.
The rig operates normally if I use paddles to key the rig.
I do use the PC for normal CAT via the serial port.=20

I have tried ferrites on the key line. I have the rig and the PC=20
connected to the same power strip. Everything in the shack
is connected to the same single point station ground.=20

I pulled the serial cable and it has no effect.

Rig works fine in SSB.

I am using a simple parallel port interface with
just a 2n2222 and 1k resistor. Should I be considering
something else?

I called Yaesu and the tech there has no clue, not even a guess as
to the problem.

Any ideas?

Tnx and 73,

Paul N1PA

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