ICD2 is working... almost

I swapped out the 4550 chip in my ICD2, and hooked it up to my work laptop.

After it went through adjusting to the firmware, MPLAB was able to connect me to the ICD2.

I was prompted to download the proper operating system for the device which I did - I hope that was the right thing to do.

The ICD2 connects to my laptop, but it failed the self-test. The only part of the self-test it appears to have failed is that the MCLR Vpp indicates as "low." Is that a problem? If so, what can I do about it?

How low does it read? My Inchworm used a fixed VPP about 13V some clones have a programmable VPP (any 8pin ICs on your clone?). Your power supply may be too low depending on how it generates HV.

The 4550 is nothing more than a USB to parallel bridge, all the interesting stuff is still done by the 16F877.

PS until you program your replacement 4550 shut down MPLAB before unplugging the ICD2 just to be safe.

Based on my semi-controlled observations, it seems that if I let my laptop go to sleep (as a result of being inactive with it), the target Vpp falls to about 3V when it's woken up again.

When I first boot the laptop and connect the ICD2, everything appears to be working okay, with the target Vpp around 10V. I think I'll try programming some chips, and see if I can find a way to keep the laptop from going into standby mode. I wouldn't mind doing that anyway, because it had a habit of going to sleep too quickly when not on the job. But what are you gonna do? It's a government computer!

Ahh some USB chipsets don't sleep well. Go to your control panels power setting and turn off standby. 10V is enough for most modern PICs, 13V is best for the antiques like the 16F84