Anyone who does repairs on Heath, Drake or other 3-500Z ham linears has probably heard about the (we hope) temporary closing of Harbach Electronics. Jeff is a supplier of many a rare item needed to keep old steam-powered gear on the air.
Until a flood inundated the work area for his "Harbach" operations.
Turns out his build-it-in soft key for the Heath SB220 is a unique product. Didn't find an alternate source when I was asked. Doesn't mean there isn't one, just means I failed to find one.
I'm not quite ready to build and sell a batch of these, but I drew a schematic of the thing from some pics I had taken a while back. It's a clever design, and has a reputation for holding up well.
Just one problem. Forgot the type number of the MOSFET that controls the relay coil. The NPN transistor could be any small NPN, pretty much.
Rather than put it off until later, here's the circuit if you want to build one yourself. Later is when I'll get back to work and retrieve the missing MOSFET part number.
Pretty sure it's right. Here's what the component side looks like.
And the solder side.
One last thought: This is *NOT* the one that goes inside the Ess-Bee two hundred. Different amplifier, different circuit to match the relay circuit it uses.
73
Until a flood inundated the work area for his "Harbach" operations.
Turns out his build-it-in soft key for the Heath SB220 is a unique product. Didn't find an alternate source when I was asked. Doesn't mean there isn't one, just means I failed to find one.
I'm not quite ready to build and sell a batch of these, but I drew a schematic of the thing from some pics I had taken a while back. It's a clever design, and has a reputation for holding up well.
Just one problem. Forgot the type number of the MOSFET that controls the relay coil. The NPN transistor could be any small NPN, pretty much.
Rather than put it off until later, here's the circuit if you want to build one yourself. Later is when I'll get back to work and retrieve the missing MOSFET part number.
Pretty sure it's right. Here's what the component side looks like.
And the solder side.
One last thought: This is *NOT* the one that goes inside the Ess-Bee two hundred. Different amplifier, different circuit to match the relay circuit it uses.
73
