Attached is another version (simpler design) that doesn’t need a separate power supply.
https://www.eham.net/article/23070

There is a company Harbaugh that makes upgrades for older linear such as the Heath SB series.
mike 
----- Original Message -----
From: Dennis Mason <[email protected]>
To: Marshall County ARC <[email protected]>
Sent: Sun, 08 May 2022 18:07:08 -0400 (EDT)
Subject: [MCARC] Fun day

Guys …   IF someone desires to use one of the “older” linears on a newer rig, there is a consideration of the compatability.  The old linears , like my National and Heathkits have about 50 volts or more for keying them up.  A friend in Lincoln bought a Heathkit SB 200 and the keying voltage was 120vdc, too much for new rigs.  Today I built a converter that inserts between the old linear and new rigs with only about 17v dc keying.  Neat thing was, all I had to buy was a transformer at Hometown lumber.  (about $27.00)  Photo showing:                     Dennis

 

 

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