Quote Originally Posted by HenrikOlsson
The help file for the PicStartPlus said to put a 1k resistor between pin 7 (AVdd) and pin 11 (RC0) on the 2431 when programing.
Where did you find that and in which help file ?

I just checked the release notes for 7.40 and 7.42 and the only reference to a resistor is

Programming PIC16F818/819 Devices
When programming a PIC16F818 or PIC16F819, you must add a 1kohm resistor between MCLR and GND. This can be placed in the socket with the device.

However in the 7.42 release notes I noticed the following...

Firmware version 4.50.01 will be available in the near future.

... hopefully that will fix some of these problems.

I did that and now the device erases and blank checks OK. RTFM, RTFM, RTFM..... ;-)
Yabba Dabba Doo

Will try it on mine later. Did you just need the resistor or did you need capacitors as well.

There I discovered that I had to order the PUM-unit from Microchip to retrofit my 1996 model PicStartPlus
I wonder if this specific problem is related to early programmers. Mine isnt quite that old but I did once replace the PIC and then later fitted the PUM unit. Not entirely sure when I got mine but the label on the bottom says

10-00157-R9
JIT980123357

So having seen lots of serial number labels over the years I am going to hazard a guess at "Jan 1998" or "1998 Week 01"