As mentioned on the previous page, in 1955, if you wanted a microwave oven, sorry..."electronic oven", in your kitchen, and you had deep enough pockets, you could order a Tappan RL-1. A little Googling will show you lots of pics as a number have survived thanks to being built-in and not easily junked without leaving a large hole in your kitchen wall. Other major manufacturers, not quite ready to jump into the market with both feet, sold the RL-1 with their own badging, knobs and minor trim changes. Whirlpool-RCA, Kelvinator and Westinghouse all pop up from time to time.

The early units were air cooled and utilized a Raytheon QK-707 magnetron. Like the Radarange Mark V, these had mercury vapor rectifier tubes which required initial warmup before use, so operation required a little planning. On the other hand, these MWO's all had a broiler element that could be used in conjunction with microwave energy to achieve browning and speed overall cooking. This idea resurfaces every few years, but unless you're doing actual meal prep with your microwave, it only adds cost and complexity (see also the Radarange Plus).
 

Curiously, the slightly later RL-1's are liquid cooled. They use Litton magnetrons, liquid-cooled transformers and small radiators; glycol circulation is by a small pump driven off one of the blower motors.

While never a major success due to cost (+$10k in 2023), variations of the RL-1 continued to be offered into the early 1960's. Tappan even introduced a high/low cooking center with traditional oven on the bottom, stovetop burners as usual, and an eye-height upper oven that was a microwave. Typical for the 1980's, but this was introduced in 1962! The power supply and magnetron were in the base where a pots/pan storage drawer would be found on a traditional setup, and a waveguide ran up the back! Spendy, but no holes in the wall required, and service was much easier. Just slide the unit out and unplug. GE later offered a conventional styled range with microwave power supply built into the same storage area, but with the magnetron in the main oven. These really did provide the best of both worlds, but required old dogs to learn new tricks, and never gained much traction. At some point I'll add pics of my GE.
 

Power Control Chassis; relay logic + time delay tube	Back of timing chassis, fluorescent starter, antenna motor & test switch shown.	Safety First! Laser cut plastic shield over HV terminals allows operation with back removed. Added inline breakers and new cord.

So what's the deal with this Tappan 1000?

The story that goes along with this microwave was that it was originally installed at one of the service areas on the Ohio Turnpike back in 1962. These were set up with vendeterias, "automat style", where you'd purchase a pre-packaged food item, locate an open microwave, insert said package and press the colored button corresponding to your purchase. Each button is set for a different preset cook time, but unlike the Radarange Mark V, the timing system is entirely electronic using adjustable RC circuits. But the differences don't stop there. This commercial model lacks a broiler element, has an interior light (fluorescent!), and the recipe card file located between the front air grilles has been replaced with special badging on a swing-away door. For the intended environment, the entire oven is slipped into a stainless NSF-compliant case, meaning technically this thing has two consecutive back panels, and a lot of extra weight! Note the unique fiberglass serving tray and chrome wall supports.
 

Step 1: Build a steel cart to handle the 350+ pound unit. Tractor loader was required to lift the Tappan into position.	Neon indicators confirm your timing selection.	Post-restoration. Conventional timer on right.	Cooling system rebuilt with silicone hoses. Copper cylinder is supply tank for coolant.

Since these were intended for 24/7 service, once powered-on, the unit stays in stand-by mode, with magnetron filament lit, one blower motor running, antenna/stirrer rotating and interior light on. Once 'start' is pressed, the other blower motor/water pump springs to life and high voltage is applied. One more thing....unlike the consumer models these also have an end-of-cycle bell to let you know you're ready to roll.

The commercial version was also designed for service: the upper panel with controls is removable, and reveals two plug-in chassis that install from the front. One handles timing, the other power control, including HV delay on startup to prevent magnetron damage.

When the Turnpike was updated many decades ago, a crew was hired to remove/demo all of this equipment including the microwaves; this one survived, and may be the only one left. It's now restored and operational.

A brief demo cooking a couple of potatoes; you can hear the bell signal at the end.

A video of the cooling system in action. A pair of radiators sit below the oven cavity towards the front, each having a cooling fan on the backside. The black pump shares the left fan's shaft, which is only powered when cooking. The Microtron unit at the top houses the magnetron tube and electromagnet. Transformer bottom right is also liquid cooled. I found RV antifreeze to be a close chemical substitute to the original coolant.

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Cory Heisterkamp 2/2024