USB Programmer: Failure to Program

[fowardbias]

After programming various chips, including "J" series, I tried another program with a "J" chip and everything seemed normal but the code failed to load? I can view the program space and it's blank. There was never any smell of a short or any other sign of failure. I would like to find a schematic to aid with the repair since I can't afford another programmer. I am unsure about the power supply layout for generating the programming voltage. L1 has a R of about 2 ohms and all the R's are good. Unsure about the little switching transistors. Any help will be appreciated since this has shut me down. Thanks JC.

[Darrel Taylor]

In meProg, go to View > Volts and click the "Read Actual" button.
If it shows a good VPP voltage then the charge pump is working. (L1 is part of the charge pump)
And if the charge pump was not working, the LED would flash RED on power-up.

It is very difficult to damage a U2 programmer, unless you didn't get the plastic case and shorted the board out on something.
Look for other causes first. Try a different chip. Try a different part number. Use a programming adapter, if you are programming in-circuit now.

The schematic for the U2 will never be released.

[fowardbias]

Thank you for your reply. I have tried the 40 pin adapter with a another chip and the results are the same. Voltages are 5V (good).Since the schematic will never be released I'll try to work with as much as I can see and document. As a general question,(hopefully not this case) if the USB's 18F2550 were to be bad, could I replace it with another? Will the programming software load into the new chip or is there a ID Lock set? Again, just a general question and thanks. RC

[Darrel Taylor]

No, you can't replace the 2550.
It needs to have firmware installed on it before it can update the firmware.

If you were able to connect to the programmer and read the VPP voltage, then the chip is still good.

I have tried the 40 pin adapter with a another chip and the results are the same. Voltages are 5V (good).

The VPP voltage is normally higher, but it depends on the chip you are programming. Which chip are you using in the adapter.

Is it the 840Z adapter?
Is it a 28 or 40-pin chip?
If so, verify that the ribbon cable is connected to the 10-pin header on the opposite side from the ZIF handle, and that pin 1 is next to the ZIF handle.