Hi Aurangzeb Haque,
To simplify the schematic I have redrawn and can be seen
at http://members.aol.com/cpu8052/vpp.gif.
I have also sent an email (asimkhan@sat.net.pk) to Mr.
M. Asim Khan asking him for the clarifications. This
will confirm your saying the email account is valid or
not. So far I have not had my email returned.
Looking at the voltage as defined by the manufacture
there would appear to be some differences. I don't think
this would make much difference in the final results.
Let see what Mr. M. Asim Khan has to say before a final
answer is made.
The solution requires careful analysis and time. I will
look over the details some more during the next few days
and give you an answer.
Regards,
Charles Bannister

The instructions for setting up the voltages are:
For the adjustment of P1, P2 and P3 use a digital multimeter & follow the steps shown below,
1. Connect power to the programmer & start the program, in the Help menu select the Adjust
Voltages option, move to Vcz Setting menu.
2. Select "Vcz 6V5" option, adjust Vcz voltage to 6.5v across pin 20 & 40 of ZIF using P1 variable.
3. Also check the 5v output across pin 20 & 40 by selecting the 5v option .
4. Move to Vpp setting options, select "Vpp 12V75" option, adjust Vpp voltage to 12.75v across
pin 20 & 31 of ZIF socket using the P2 variable.
5. Next select "Vpp 12V0" option, adjust Vpp voltage to 12.0v across pin 20 & 31 of ZIF using
the P3 variable.
6. Re-check all the options in Vpp Setting menu.