I bought a Dual power Willem eprom programmer from Mcumall several years ago, mainly for burning 2716/2732 eproms with no problem at all. Last week I wanted to burn a 27C512, so I set up the right Vpp and Vcc, but couldn't burn the eprom. After several tries, I started to check if everything was OK on the burner side. So I checked Vpp and values were off range. Then I went to my computer BIOS and set up the EPP printer port mode, but I had Vpp values off range too. So I started checking all possible combinations of Vpp and Printer port mode, and the results are in the attached picture (DMM = Values I got with my digital multimeter when checking Vpp values).
Is there a problem with my EPROM programmer? What components should be replaced when I get these values for Vpp? Should I give it a try using another computer?