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Home built PickIt2 not behaving


Dec 7, 2012
Dec 7, 2012
Hi All,
I am having a strange problem with a homebuilt PickIt2. It is wired just as MicroChip designed it, but I substituted a few parts to facilitate thru hole construction. I subbed a BS250P P channel MOSFET for the IRLML6402 and the Q2 part of U5, and a TN0702N3 for the Q1 part of U5. I also subbed a MCP6041 op amp for the MCP6001 op amp. The board is recognized by the PickIt2 v2.61 software. The problems are as follows:

1) When first plugged I get the error message bo that says "Pickit 2 VDD voltage level error. Check target and retry operation." I get this error message whether a PIC is connected or not.

2) When I hit OK the PickIt 2 Programmer software runs and shows that a PickIt 2 was found and connected. Sometimes it finds a connected device, other times it doesn't.

3) If it finds a device, pressing Erase or Blank Check brings up the VDD error box again, and then the software reports "No device detected".

When I run the troubleshooter, the following occurs:

Step 1 passes but I always have about .2V difference between what I set and what I read in the results box and on my DMM.
Step 2 Pressing "Test VPP" the first time gives me a "Test Failed: VDD Short Detected" error. I can see with my scope that the level is high, and I can measure around +12V with the DMM. If I press "Test VPP" a second time it reports that the test passed with a voltage reading close to what I get on my DMM. When I press "/MCLR On" the VPP level drops to 0.
Step 3 I can control the PGC and PGD lines during step 3 testing.

I feel that Step 2 is the main problem, but tracing my connections has shown no miswires. Plus if there was a miswire, just running the step a second time would not pass the test.
Did one of my substitutions break something?
Any ideas on how to get this working would be greatly appreciated.