A Literal "Barn Find" Heathkit SB-200 Amplifier Lives Again, Thanks to Don Kiser's Restoration

Controls engineer Don Kiser has restored a "barn find" Heathkit SB-200 radio amplifier to its former glory — and he's using the term entirely literally, the device having been rescued from a literal barn.

"Brian O’Connor (KA2CGB) made a trip to Ohio to visit a friend [in 2007]," Kiser explains of the radio's origins. "It was at this time Brian became in possession of a rather unassuming and slightly grotesque, Heathkit SB-200 that 'been in his (friend's) barn for a long time,' Mr. O’Connor recounted to me, one fine evening, via electronic mail exchange. It was destined to be modified for 6 meter but little did Brian know that day would never come. It was somewhere in Brian’s domicile that the SB-200 sat. Untouched, year after year. Eventually, it came to live in the corner of a RARA storage unit, long forgotten until the year 2022."

The concept if a "barn find" will be familiar to those in the world of automotive collections, referring as it does to a vehicle — typically a car, though sometimes a motorcycle, light aircraft, or even a military tank — which has been stored in a barn with little shelter from the elements. Such vehicles require considerable rebuilding to get them back to functional order — and that's exactly what Kiser, having relieved O’Connor of the barn-find radio courtesy of a free-goods table at a RARA Hamfest in 2022, had to do.

"I came upon the boat anchor noticing it several times throughout the day," Kiser recalls. "It was near the end of the day that I decided to take the thing home.The faceplate barely had any paint left. I knew it to be a Heathkit but wasn’t sure exactly what it was. 'It's an amplifier,' Brian said. 'They’re good for modifying for 6 meters,' he added. I was curious and decided to take it home."

The Heathkit SB-200 is, in fact, a linear power amplifier for high-frequency radio use launched in 1964 and discontinued 14 years later. Designed primarily for 80 to 10 meter HAM band usage — though, as O'Conner claimed, frequently modified for 6 meter use — the amps can push out up to 700W — but not, usually, when they've been left to corrode. Kiser's project box had lost most of the paint to its faceplate, and was filled with grime — hiding, pleasingly, intact vacuum tubes.

"After copious amounts of contact cleaner, alcohol (denatured and medicinal), canned air, and agitation the first cleaning was complete. It [was] starting to look better but definitely not ready to go on the air. I cleaned up the case and painted it a 'matte deep gray.' Along the way I repaired the dents and dings to give it a better than new look. I also replaced the original fans with two 120VAC 80mm fans capable of 43CFM [Cubic Feet per Minute] each."

"All the capacitors were replaced with new," Kiser continues of his restoration work. "The resistors were replaced with the appropriate type.The parasitic suppressors were NOS carbon composition to keep the top looking period-correctish and other compositions can cause issues. The visible aluminum surfaces were cleaned, sanded, and polished. A new HV wire was installed good for 45KV. A new 12 AWG 20 amp cord set was added."

With the restoration complete, Kiser was able to test the restored amp with a dummy load — finding it outputting near-600W on a 100W input. "All-in-all I was surprised how simple the design of this amplifier is," he notes. "I did get lucky that its ugliness was only superficial. The meter still working was a plus as these are near Unobtanium. The tubes are in perfect condition. The project cost about $250 to complete, a bargain any day. I now urge you, the reader, to take on that project sitting in the corner collecting dust."

Kiser's full write-up is available on Hackaday.io.