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Heathkit Jr Electronic Workshop "35", Model JK-18 |
The Heathkit Jr 35 evidently had been stored with batteries in the battery holder, which corroded badly. I replaced it with a plastic RadioShack 4 D-cell battery holder (270-389), wired into the negative power rail and the hot side of the power switch (which is part of the variable resistor).
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Corroded battery holder |
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Replacement battery holder mounted |
I mounted the replacement battery holder with a dozen "heavy duty" 1 inch foam double-stick mounting squares (rated to hold 900g), stacked in four groups each three high to overcome the various screws protruding through the main board.
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The remote speaker station |
The rubber foot used to protect the relay from being crushed when you turn the kit over was stuck to the remote speaker station. I put it in its rightful place.
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Relay with the brown rubber foot |
Earlier, I had built a couple simple circuits, which showed the meter and new battery pack working, but showed me the telegraph key switches were not making good contact. I used a Scotch-Brite scrubbing pad to remove corrosion from the key switches on the main board and the remote station.
I ran through the tests in the manual appendix to check out the lamp, power switch, speaker, earphone, antenna coil continuity, remote station speaker & telegraph key, slide switch, and relay.
I then jumped ahead of myself, building the 4-transistor AM radio experiment; I got slight hints of a audio signal if I wiggled and touched some of the wires. I'm highly suspicous of the electrolytic capacitors. I probably should have tested those (and the transistors) before using them in such a complex circuit. The wire connections to the springs are not all that reliable, and the wires might have some oxidation on them.