Comments for page: 1702A EPROM Programmer

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Posted by Va3qe February 03, 2019 - 02:37 pm
Yes it is running DOS 6.22 natively (from a bootable CDROM. I sent you an email with more details.

Thanks for you offer to help.

Posted by Steve L. February 03, 2019 - 01:28 pm
Hi Va3qe, Sorry you have a problem with the project. I'll be happy to help with the debugging. I trust that DOS is running natively on the PC and not under Windows or another OS. You mention that the read LED comes on as soon as power is applied. I take it that you have the computer and the PROMPRG program running when you apply power to the PROM Programmer Hardware (PPHW), is that right? This suggests that there is a logic high on pin-16 of LPT1. Do you see +3V or more there? PROMPRG should be setting that pin LOW initially, so this is something we can troubleshoot. To facilitate that, please contact me at the email address seen after you click the About button near the top of the Home page. We'll get to the bottom of it!

Posted by Va3qe February 03, 2019 - 11:15 am
I finally got around to building one, but I am having trouble getting it to read or burn EPROMS. I have checked the wiring and I am reasonably sure it's correct. The second LPT port seems to be working. Its setup as BPP.

For reading, it always says the results are all 00's. The read LED come on as soon as I apply power.

When I try and burn an EPROM, it appears to be doing it, as inner the relay clicking, but I don't see the write LED lit, and when I read the EPROM using another reader, it shows blank.

Running DOS 6.22 on an older Pentium machine.

Any ideas what to check next?

Posted by Steve L. June 24, 2018 - 08:37 pm
That sounds like an excellent project. I'd be very interested in covering it as an addendum to the article if you're up for that (with full credit of course). The serial interface would be SO much easier for folks to use these days. Feel free to contact me if I can help in any way. My email address is on the about page, accessible with the button on the Home page.

Posted by Andi8086 June 24, 2018 - 06:02 pm
Thanks :) That makes sense then. I am currently resdesigning it with an Atmega Microcontroller to which I want to talk via serial. I will be happy to share it if it works.

Posted by Steve L. June 24, 2018 - 03:46 pm
Hi Andi8086 and thank you for the interesting question! The answer lies in the fact that the Vgg pin of the 1702A is expected to source current during the programming. The programmer hardware only needs to pull it down or let it go to the +47V rail. Since the specs require that it only be pulled down to about +10V, the Zener is placed in series with the pull-down driver, Q1. I will be happy to help if you have any other questions.

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