Twilight Zone
Bally, 1993I got a U14 check sum error on my TZ. I first replace the U14 eprom (it was bad) and still got the error. I found that U15 was also bad and replaced it and still get the same U14 error. U18 checked out good. I'm running L2 sound and 9.4 H . Tried reseating the cables and chips on the sound board. There is nothing obvious wrong with the sound but because the 2 eproms were bad I think I should track down the problem. Any ideas?
I have one DMD pin that Always give an checksum error, apparently it is generated because the soundboard installed is of a later version then should be. Sound however is working fine, so never replaced it
Thank you for that info. Many people, as myself, do not have an Eprom burner.
At my company, when we used Eproms, we always cleaned the window with alcohol and erased the part 2 times in an Eprom Eraser before reprogramming.
Quoted from PinballManiac40:we always cleaned the window with alcohol
After removing the label I've seen EPROMs with a large amount of adhesive left behind. I've used Goo Gone (and lots of elbow grease) to get the remainder of the adhesive removed. It is imperative to remove all the adhesive before attempting to window erase the EPROM. I've had one in the past where there was remaining adhesive and it didn't erase correctly until I removed the adhesive.
Quoted from ripple:Both U14 and U15 image did not match using my Needham's Eprom burner. U18 did check as a good match. I triple checked U14 and tried burning 2 different Eproms and still get the error.
So reading the original U14 and U15 in a writer attached to computer resulted in a mismatched checksum compared to the known good "master" image?
U14 should be $A08A
U15 should be $9588
I assume you did the following:
- Write a new clean image for U14.
- Tried it in the machine.
- Still produced U14 checksum error.
- Removed U14 and verified in the EPROM reader that the checksum still matches.
- (For grins and giggles) Tried it again in the machine to verify the result reproduces.
If you've done that then there's definitely a problem on the board. I'd check all 32 pins of the U14 socket for continuity to the correct point. Almost all of those pins are either the address or data bus and continuous with the same other pin on U15 or U18. It's really only CE/OE (pins 22 and 24) that are specific. It looks like (according to the schematic) that OE (pin 24) is tied together for all the EPROMs.
Specifically U14 is A21 connected to U28-15. If you have (static) continuity then you'll probably need to verify (dynamic) functionality. A logic probe should reveal the signal transmission on this line.
My Eprom program has a verify function. I don’t know how it exactly works but both U14 and U15 did not verify as matching the program, U18 did match fine. I did double and triple check U14 and tried 2 different chips with the same error. I did check continuity on U14 socket but I have not checked U15 or U18 sockets. I will check continuity on those 2 chips and U14 -A21 connected to U28-15. Also thinking of burning a new set of both L1 and L2 sound roms and trying them.
I don't see it mentioned here but it is always a good idea to run a blank check on your EPROM prior to burning it.
I got 3 newly burned ROM chips installed and it fixed the error. I have had a Needham's Eprom programmer for 15+ years and never quite had this problem. The 3 old chips verified as good but there must have been a problem. Also the board was also recapped and the popping noise when I turn on the machine is much less.
I'm trying to burn a 1.1 sound rom for AFM. I've got a 4mbit chip. The sound rom is 1 mbit but I'm using a D27C4001 4 mbit chip. I've expanded the rom size by doing a binary copy and burned the chip and verified but i get a S2 checksum error but sound works fine (Checksum is 1300 0x08FF)
Quoted from The_Pump_House:I'm trying to burn a 1.1 sound rom for AFM. I've got a 4mbit chip. The sound rom is 1 mbit but I'm using a D27C4001 4 mbit chip. I've expanded the rom size by doing a binary copy and burned the chip and verified but i get a S2 checksum error but sound works fine (Checksum is 1300 0x08FF)
Pretty sure that requires an 8 mbit chip. Isn’t the file one mbyte?
Quoted from jchristian11:Pretty sure that requires an 8 mbit chip. Isn’t the file one mbyte?
I couldn’t possibly make such a dumb mistake….
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