My dual power with 16bit adapter wont program my am27c1024 or at27c1024's. I used the hardware test and all seems fine with the dualpower programmer, it has programmed other eproms as well as some nvsram chips flawlessly(all 8 bit)and reads 27c1024's great. When I use the 16bit adapter to program though, VPP is dropping to 11.3x and I geat ramdom chip/buffer errors??
I am using a 21v .85a ac adapter and have my vcc @ 6.25v as per datasheet. I have also tried different twp/twc settings to no avail.. Thanks in advance
EDIT: After reading a few more post and reading a bit on willem.org I see a that the design of this board/components used for vpp supply are limiting me.. To bad I found this out after I bought my board and adapter that show specific support for my IC's.. Apparently there is a fix available but it means I WILL HAVE TO MODIFY MY BOARD! Maybe this fix should be implemeted or at least offered to your customers before they purchase?
If you can locate the source of your VPP drop, you might be able to make your programmer work for CMOS EPROMs. Load VPP with a 240 ohm resistor and see if it can maintain 12.5V. Also check VCC to see if it's also low.
The most frequent problem with that the step-up regulator is the coil. But it could also be the cap, diode, or regulator itself.
On the dual powered programmers, you shouldn't apply more than about 9VDC. Anything higher will cause unnecessary power dissipation in the 5V regulator.
It's good that you're setting VCC to 6.25V. That will give you a more reliably programmed device. If it's a used device, you should also blank verify at around 4.5V.