[1000mp] Computer Interface

[Doug Rehman]

I just finished building an interface for my Field for both CW and digital
modes. I used the circuit found at http://www.qsl.net/wm2u/interface.html
for both the CW key and the PTT. The CW key works perfectly from the
computer, but I am having a problem with the PTT line. The PTT line is
connected to Pin 3 of the "Packet" connector.

When keyed by the computer, the PTT voltage drops from 13.4 volts to about
2.7 volts- not enough to key the radio. If I parallel 50 ohms across the
opto isolator's output, it works like it is supposed to (the standby voltage
on the PTT line drops to about .7 volts, but the radio isn't keyed until the
computer keys it).

I've tried to use the CW key output for PTT, but it does the same thing so I
don't think it's a wiring or component issue.

I've also checked the ground connection- no problem (.1mV difference
according to my DVM). 

It won't key the radio from the  PTT connector on the back either.

I've used this exact same circuit before on a Kenwood TS-430S and TS-2000
without any problems.

Any ideas? Anybody experienced this before?

Hanks,
Doug
K4DDR