Hi Andrew,
Hi Im tryin to build the easy downloader v2 programmer, i have already done with the hardware, and i also have the C51 programmed with the hex they suggested (ez52.hex)

You can mail you problem to wichit He is a very nice chap and replies allmost all e-mails.

i get online with the software version Ez3, but after i chose the hex file to be downloaded, i have an erase error at the begin of the programmin after the ten attemp, what may be the problem?,

In Easy Downloader ver2.0 The Voltage on EA/VPP pin is given using LM317 and its output is +5V for reading and varifying but for erasing and programming the output is switched to +12V using a transitor. Check the voltage at Pin 31 of the slave micro that is the one being programmed while it is erasing.... If it is very likely below 12V.

im using a regular 12V source, instead of the 15V source suggest
LM317 has an internal drop of atleast 3V thus the supply voltage needs to be atleast 3V more than the output desired in this case as I mentioned in the earlier paragraph the maximum output desired is 12V thus the input supply must be atleast 12+3=15V.

Has somebody else made it work?
Yes, I have made and used it earlier and it works.

Regards,
Prahlad Purohit