Do I need a "soft keyer" or buffer to use my Heathkit SB-1000 Amp with K3?


Christopher Scibelli
 

I have a Heathkit SB-1000 KW HF amplifier. It is actually an Ameritron AL-80. Ameritron sells what they call a "buffer" and others call it a "soft keyer". Ameritron has an article on how modern rigs can be damaged by older amps due to high voltage and/or current on the key line. I ran the Amp with an Icom 735 for about a decade and it did show the signs that Ameritron warns about. The relay (I'm not sure if it is the one in the amp or the T/R relay in the rig) would get stuck and naturally receive signals would be greatly attenuated. If I pulled the keyer line out of the RCA jack from the Icom and gave it some quick taps against the Amp chasis (grounding it)it would "unfreeze". Sometimes some very high speed dits from the keyer would unfreeze it. I should have investigated this when it started but the very fast dits would usually quickly restore things to normal and to be honest, I did not know what was causing it. I haven't used the Icom in years but when I hooked it up last week the receiver was virtually dead, but transmit is OK. I think the T/R relay in the 735 is shot but it's just a guess.

Can I run the K3 with the SB-1000 or do I need a "soft key" or buffer? Hamgadgets.com has a $15 simple kit which seems to do the same thing as Ameritron's buffer. It is described as follows:

"Operation is simple. Input from your straight key, bug, computer, electronic keyer or external T/R output of your transceiver controls the input of an optically isolated solid state relay with back-to-back MOSFET outputs. An LED lights whenever either input is active so you know when the output is on. The output is optically isolated from the input - no more "hot" keys on the operating bench, and no more blown components in your solid state transceiver from keying that SB-series amp. Best of all, you get completely silent operation and turn-on times around 2 ms or less."

Lastly, can somebody kindly describe exactly what is happening when I press the PTT on the K3? I was under the impression that up to 200 volts at 5 amps was being generated by the Amplifier and that my Icom has been damaged due to excessive current from the Amp but it is confusing to me, anyway. I apologize for the length. Blowing a part on a 20 year old rig is one thing but I have to make sure the SB-1000 will not damage this beautiful rig.

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