Tuesday, 14 June 2016

Don't Try This At Home

No, seriously, I do mean it! Alright, so this is a project that I hope, sometime in the future, other radio hams may copy, and add modern amateur like VFO control to their vintage Clansman PRC-320 HF manpacks...

... but, until I can demonstrate a working system, please dont try to copy what ive done so far!

The reason I say this, is that part of the mod is to add nineteen (yes -19!) additional wires to the module 9 synthesizer pins. Even following the recommended method of accessing these pins as detailed in the EMERs, this is a seriously difficult task! Just simply dont attempt it, unless, like me, you can do it to a spare radio, and that you are prepared to knacker that radio up!

There are nine connections to be made to the lower bank of pins. Three of these are around the lower right corner, where the wiring loom is densest, and access is nearly impossible. Expect to scorch or melt insulation! There is also a clear plastic insulating film to deal with, and also ensuring that the pins dont bend and short out on the casing!

Ive used two lengths of ribbon cable to do this. In the photo above, ive got that awkward corner done, and about half the remaining lower bank. It is essential to match up the pin numbers with the diagrams and the cable loom wire numbers! Ive loosened the bolts on the 1kHz module to the left, just enough to be able to move it slightly.

In the 2nd photo, ribbon cable A is completed. Thats the hard one! I found that wherever possible, tinning the pin was very helpful. As was the use of surgical locking forceps to hold the wires in position, and an eldest son to hold a high power torch! The big problem is light - without help I found I could either see what I was doing, or attempt to solder, not both!

And in photo 3 half of ribbon cable B is now connected, this has ten connections to the upper bank of pins. On this one im cutting the individual wires to length to keep the body of the ribbon as close to the module as possible. Its also essential to make a written record of that pins connect to which wires on the ribbons!

Five wires remain to connect. With luck, ive managed to solder them all to the correct pins, and made a reliable connection to each. Time will tell!

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