photograph of board after modification

modifying a velleman K8048 by plugwash

I had several spare picsquirt boards from the various prototying stages and i have a friend i'd like to inroduce to the modern 18 series pics, but i didn't have any spare demo boards.

so i made the descision to buy a velleman K8048 (mainly because it was cheap from rapid) and modify it for use with the picsquirt. The plan was to remove (well not build, i bought the velleman board as a kit not assembled) the inbuilt programmer (which was serial and its software did not support 18 series pics), fit a polarised molex kk connector for programming in the conviniantly supplied land (intended for using the velleman board as an in circuit programmer but perfectly suitable for the opposite role) and add some extra decoupling (in the form of a surface mount capacitor directly between the socket pins) so a PIC18F2550 can be run on the PLL. The run/program switch was bypassed and the pullup to Vdd was increased to 47k to ensure the programmer could pull it up to 12V. the replacement resistor is rapid code 64-0118, the extra cap is rapid code 71-1380

Building mostly went to plan, there was one mistake in my layout modification (caused by incorrect determination of the switch behaviour). I have corrected this on the layout now and the changes are visible here (on my board i used a different correction involving one of the pads of the left out ZD1 because i lost a pad during desoldering).

to solder the surface mount cap in i first soldered one of the relavent pads on the IC socket, then i reheated that pad while introducing the cap (with reverse action tweezers), then i soldered the other pad.

I have now done this mod twice and both boards work fine.

modified schematic
modified layout