VCC refers to a voltage rail. It will be testing all possible voltage ranges that it can supply for programming. From the specs this unit creates "Programmable VCC from 1.8V to 6.5V, VPP from 1.8V to 18V chip"
I had a look in mine, directly behind the USB socket are 2 small inductors, these may be used to create voltages. Further back are 2 much larger inductors that are likely where you need to look. The related components are under these. Look carefully for physical damage, bad soldering etc. Mine has a SMD cap ripped off after it had been soldered on. Not the best quality control. Lucky for me it's not necessary.
You could probe the output of these switching supplies with a DMM or scope during the self test to see what voltage appears. I would expect a few steps in quick succession as it sets a level, measures it, then sets the next in order to test itself.
Good luck
Jonathan
OK OK I'll probe mine so you know what you should get
During test (USE A SCOPE, DMM won't show these pulses they're very short) and probing the ZIF socket
pins 1 to 5 show pulses in this order 8.5V 4V 2V 4V
6 8.5V 4V 2V 8.5V
7 to 10 8.5V 4V 2V
11 to 16 4V 2V
17 to 20 2V
21 to 29 4V 2V
30 to 40 8.5V 4V 2V
Pulse widths are about 10ms with the 2V one being about 170ms in all cases. If not getting this you should trace your way back through the circuit from the zif socket and you should come to the source of the pulses and find out why they're missing or out of range. If they are all present and correct then the feedback lines must be bad and the micro can't see the values.
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