I must be doing something wrong. I'm UVing 27C256 (some 'A' and 'B' suffixed) PROMS until they're almost baked, and still some do not read them as blanks. The ones that are checking as blank are reportedly having programming errors during the burn. Anyone have this issue?

I can burn 27C128s all night long without incident. I'm burning a stock AUJP.bin just to try it.

I know - I'm an idiot. It's probably something obvious, but none of the documentation I've read is any help. Board Searches have given me ideas, but have been fruitless.

 

How old are they? age and number of "burns" to take their toll on chips. It's quite possible you done nothing wrong and the chips are just done.

 

Same problem here....probably just done

 

This is my solution to your problem; 29C256 . I've done about 100 reflashs on these babies. Best $6 ever spent on this DIY prom burning hobby.
How many minutes are you baking them and at what temperature (does this sound like a cooking show). I've had troubles with some old 2732a's in cold weather for 5 minutes. They needed 10 minutes. 20 minutes and they were dead for good. Very annoying hence the evolution from UVE to EE Good luck

 

10-12 minutes on BROIL, err, under a generic eraser. The **** on the timer is a little sloppy, so it is a little tough to determine the actual time. Not that it was ever a precision instrument, mind you, but it looks like about 10-11 or so. They've been erased about a half dozen times. Looks like it's time for E²PROMs.

 

Well, that should teach me to be "organized". I finally broke down and read the PP2 instructions again. Apparently, my recent cleanup of my office caused the problem. I had moved the PC, both printers, flat scanner and of course the PP2. In the process, I installed some longer cables. PP2 instructions explicitly state NOT to use a round parallel cable for extending. I had been burning 27C128s with no hiccups, but banged my head against these 256s. After "uncleaning" the office and plugging the PP2 directly to the #4 parallel port, I was able to burn both the new 27C256s and the old ones that had been erased about eleventy-jillion times.

As much as I hate to admit it, I actually had to read the instructions.

They must really mean what they say about the cable routing and arrangement. If you're having troubles, it might be something to check.

 

Vader, FWIW, also keep anything that can create ESD out of your work area too. Vinyl folders, plastic bubble wrap (not pink) etc. I learned this the hard way. I also store my eproms in antistatic foam I bought at Radio Shack.

 

My spares that aren't in the eraser are in antistatic sleeves with some RAM DIPs (bulk pack). That's mainly to protect the pins from damage on the desktop.

I might be stoopid when it comes to following instructions, but I'm fairly versed on ESD protocols. I have Red Wing work shoes with ESD dissipating pads in the soles (with the little green "ESD" tags on the tongues). UVPROMs are fairly impervious. It's the CMOS stuff that requires a bit of caution.