On Sun, 4 Jul 1999 16:06:41 -0400 "Jack Trampler" <email@example.com> writes:
>Recently my FT-1000MP took ill and I had to return it to Yaesu. I
>on this reflector about keying the Drake T4XC with the keying circuit
>appears in the TR manual. I received many replies (thank you to all)
>there were two routes to choose from.
>Since the Drake uses grid block keying, the first option was to change
>transistor to a PNP type capable of handling the keying voltage.
>measured -34.5 volts at the key. The problem with this option is when
>comes back I will have to change the transistor again.
>The second option was to use the existing circuit to key a relay.
>>I believe the C-line uses -60 to -70 volts DC for grid block keying.
>>such the polarity is wrong, and the voltage rating would be exceeded.
>>simplest fix probably is to put a dip relay in the collector, provide
>>volts to operate it, and use the relay contacts to key the C-line.
>I decided to go the route of the relay as it will be compatible with
>rigs. I used a Radio Shack 5VDC reed relay (part #275-232) with the
>connected between the transistor collector and the junction of pin 17
>the 1K ohm resistor that goes the emitter. Pin 17 supplies 5 VDC.
>tested this relay up to 50 WPM and it works very well.
>The only question I have now is the relay draws 20ma. Will this
>current damage the computer or serial port? I would think not, but I
>have any specs on this. If anyone know for sure, I would appreciate
Sometimes it's difficult to get an authoritative answer on a
question like this. Anyway, here's one method that Tree
recommended to me last week that will work for sure.
Connect an external voltage source to your relay, +12vdc
or +5vdc, or whatever is required. Connect the other side of
the relay coil to the collector of the transistor in the regular
positive keying circuit.
Dave Hachadorian, K6LL
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