Yes, I know about isocouplers , I used one in my wx radio adapters we had at Seneca and several spread around in schools and business.  But to me there were several other parts of function of the SB200 to consider on the “Turn on” ckt.  So I took the easier route and only added a transformer and 4 diodes, and relay.  You can’t get much simpler than that.  The SB200 had polarty issues too…. I’m getting lazy in my old age!   Dennis

Sent from Mail for Windows

From: Mike Stillwell
Sent: Monday, May 9, 2022 8:07 AM
To: Marshall County ARC
Subject: Re: [MCARC] Fun day

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

margin: 0.0in;
font-size: 11.0pt;
font-family: Calibri , sans-serif;
}
a:link, span.MsoHyperlink {
color: blue;
text-decoration: underline;
}
*.MsoChpDefault {
}
div.WordSection1 {
page: WordSection1;
}
/*]]>*/

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

Sent from Mail for Windows