Re-wiring the Palm Portable Key (PPK) and The Red Cable Mystery

 

Inspired on the famous and much larger and heavier German Junkers key, the Palm Portable Key (PPK) is a cute, small, light but very sturdy and very able straight key for transmitting Morse code.

After several years of flawless service, suddenly the PPK ceased to transmit. A survey with a voltmeter confirmed that nothing was wrong with the stereo plug or the key itself, but that in the original cable there was an electrical discontinuity between the tip of the plug and the end of the cable connecting to the bottom of the key.

The solution was to replace the original cable with a ~4-foot long piece of RG-174 coaxial cable: the outside sheath mesh was connected to the top of the key (see arrow in the picture at the top) and the central conducted insulated by the dielectric was connected to the bottom of the key (see arrow in the picture at the bottom).

PPK

The mystery that remained was the interruption in the inner connector inside the original cable provided with the key, as it is unusual for an inner insulated wire cable to break alone and far from its end connections. The cable provided with the key had three wires, one not insulated that connected the base of the stereo plug to the top of the key, and two insulated ones: a white one, which was not used, and one red used for connecting the tip of the plug to the bottom of the key. The discontinuity was clearly in the red wire. After removing it from their common PVC sheath, a white “bruise” was noticeable on its surface at about 10 cm from the end that used to connect to the key. Testing with the voltmeter confirmed this as the site of the break – very unusual.

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