Pic and ICSP

I think the 1N4448 is a typo, I use a 1N4148. It isn't essential, anyway, it just protects against reverse power connection, and the target board gets its power from the programmer when using ICSP.

I built my own JDM programmer and it seems to have problems when using ICSP with certain chips. For instance, I can't program the 16F628 with ICSP, although it programs OK using the programmer socket. ICSP works fine with the 16F88. Someone else on the Yahoo PIClist has the same problem with it.

Leon

I do something similar, 2 diodes (1 in each line), I use 1858 diodes, a different programmer (it should work the same) and my rb6,rb7 lines only go to the programmer.

Disconnect your circuit from the power supply completely. This programmer depends upon using the negative voltage of an RS232 pin as a ground. This is so the positive voltage on another pin will give enough voltage to bring MCLR to 13V (or so). If your circuit is connect to an earth ground (like thru it's power supply), you will not be able to generate the 13V needed to program the chip. Depending upon the serial port used (especially from a laptop) you may not be able to generate 13V anyway.

This is a typical problem with the CHEAP/CHEESY programmers.

My advice is to get something a bit more "correct". You will have more than enough problems to solve without having to worry about your programmer. Get a programmer that correctly generates the regulated voltages needed.