Thursday, 24 September 2009

Witlessness and woe

If I've learned anything this evening, it's how to waste three hours work on one simple detail. The new radio was laid out three nights ago, and it looked elegant, compact and concise in its prototype stripboard form. The resonators, 1K pots and 100p COG capacitors arrived today, so it all looked good for a first build. Thursday evenings are free of Sea Cadet obligations, and nothing was planned by the family. I settled down in my untidy position at my desk in the extension, and carefully loaded the stripboard. My youngest son came by to wish me goodnight at around 2100, and I was just hooking-up the tuning pot. The tuning LED glowed and dimmed, the volts were where they were meant to be, but no output from the SA602. I'd put a 100p cap on pin 7 (the oscillator emitter), to take the signal to a keyed buffer for the transmitter. I was patiently listening with my old Realistic DX-392, looking for signs of life. I searched the board for open joints, solder whiskers, anything. I changed the ceramic resonator for another type, I removed the bandsetting padder, I changed the LED coupling capacitor, nothing.

Then it hit me, like a huge, soggy mattress. I am so used to using chips upside-down on a piece of copperclad, that I'd laid the board out with the two chips back to front. The entire layout is scrap, and I face a fresh piece of quadrille paper to start afresh. Ho-hum.

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