Heathkit GD-29 (1971)
Overview
The GD-29 is the odd one out in any Heathkit collection. It is a microwave oven sold as a build-it-yourself kit, announced by Heath in late 1970 and priced at $399.95. It is not a tuner, not an amplifier, not a test instrument. It is a countertop electronic oven that a hobbyist assembled at the kitchen table, and it is one of the strangest things the Benton Harbor company ever boxed up and shipped.
Heath's own advertising pitched the kit as a cooking revolution. It claimed microwave preparation ran up to 70 percent faster than conventional cooking and preserved more vitamins in the process. The copy leaned hard on the domestic angle - a baked potato in four minutes, a five-pound roast in 45 - and on the fact that only the food heats, so a meal can be cooked on china, glass, or paper and served on the same dish. The oven runs on standard 120 VAC household current, which the marketing framed as portability: plug it in on the countertop, on a wheeled cart, on the patio, at the cottage. Shipping weight was listed at 97 lbs in one 1971 catalog page and 80 lbs in the earlier launch advertisement. Treat that as catalog inconsistency, not a spec change.
The engineering inside is period-correct microwave hardware. A Litton magnetron operates at 2450 MHz with a peak power of 650 watts, coupled to the cavity through a waveguide. A metal stirrer underneath deflects the microwaves for even heating, and a fan draws air through a rear-panel filter to keep the tube cool. The cavity measures 8 inches high, 14 inches deep, and 15½ inches wide. Heath made much of the safety design. It called the door interlock system unique in the industry: the oven stops if the door opens, and the door cannot open unless the interlock is functioning. There is also a second independent door interlock and tamperproof mechanisms throughout. The door seal is conductive vinyl, backed by a plastic door baffle and a capacitive door seal. Assembled per the manual, Heath stated the GD-29 met the then-new federal standards for safety and radio interference.
For a piece of vintage gear, the GD-29 has an unusually good paper trail in the audio press. Audio (December 1972, p.70) ran a Workbench report on the oven. The reviewer admitted outright hesitation about covering a microwave, but reasoned that it is an electronic kit and the audio enthusiast is as competent as anyone to build one. That review is the best independent source on the unit's construction and safety architecture. It is also candid about the economics: unlike most Heathkits, there was not a great deal of money to be saved by building this one. The pitch was serviceability instead - an owner who built it could also fix it - and the domestic prestige of being the person who assembled the family oven. Audio also noted the GD-29 in its annual index of equipment reviewed that December.
Collectibility is thin but real, and it is not an audio-collector market. A 1970s microwave is a heavy, mains-powered appliance with a magnetron that may or may not still be healthy. The people who want one are Heathkit completists and mid-century appliance people. Values reflect that. Nobody bought a microwave oven kit to put on a shelf, so survivors are working appliances or garage casualties, rarely both intact and original. Anyone chasing one should check the door interlocks above all else. The safety system Heath advertised is the most important part on a fifty-year-old magnetron appliance, and it is also the part a previous owner may have bypassed.
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