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Repairing a KITSRUS Kit 150 for ICSP (January 29, 2008)
In the beginning, I fell in love with the Kitsrus Kit 150 PIC programmer for it's socketed automatic programming mode. The kit was priced right, supported most of the chips I encounter, and available locally. Over the years, I've ended up with five of them.
Recently, I discovered none of them function for ICSP or 40-pin parts. (Normally I use a JDM2 clone for ICSP, this was the first test of the K150.)
Obviously, some investigation was in order.
Attaching the two-channel scope and some multimeters to the ICSP connector, it was quickly determined VPP never rose beyond about 0.04 volts. (It should be up around 12 volts.)
Thankfully, the Kit 150 schematic is readily available (perhaps the only KitRUs programer schematic available). Tracing VPP back from the ICSP connector, we find the first sub-circuit is a pnp transistor switch from +12V.
Some more probing with the multimeter shows all the resistors check out. More probing (with the circuit running) shows the transistor in question (TR2) never conducts.
A closer inspection of the transistor (and the schematic) shows it's a BC856B. Thankfully, I have some on hand, but there's nothing magical about these, most PNPs with the same pin out will work.
Replacing this part is blissfully simple. Without a rework station on hand, I used a conventional five-dollar-special iron. Hold your iron across the left-two pads, until they're molten; lift the two pins away from the solder. Repeat on the right-side pin and remove the transistor.
Since this is little more than a switch, the AC performance isn't critical, and since VPP carries marginal current, the DC resistance isn't critical either. If you're feeling neat, you can remove the existing solder, clean the pads, and add new solder as you go, but you'll be fine if you leave the old solder in place. Simply melt the old solder-pools and press the new transistor in.
Howto (9) Kit (11) KitsRUs (1) PIC (8) Programmer (2) Repair (1) Solder (2)
Posted by spiffed at January 29, 2008 8:39 PM