Programmer Modification - PIC18Fxxxx devices

If you have problems programming an 18F series PICmicro, it may be necessary to add a small capacitor to the output connector (J3) of the programmer, or to the target board, if the device is being programmed in-circuit.  (If you already have 0.1uF bypass caps on your target board, it isn't necessary to add more.)

This modification can be performed on either EPIC Programmer or melabs Serial Programmer.  The additional capacitor will not degrade performance for any of the unaffected PICmicros.

A 0.1uF monolithic capacitor should be added between Vdd and ground. The best place to add this capacitor on the programmer would be on the back side of the board soldered directly to connector J3 between pins 4 (Vdd) and 10 (ground). The addition of this capacitor does not interfere with the programming of other devices.

This modification can be done to either the EPIC or Serial Programmer.

Back of programmer PCB
(EPIC programmer shown)