Quick update to my Omega build. CPU swap and LS00 swap with new chips from Mouser did NOT work. I pulled a different IC out to see if I could get the Memory error, but still black screen, so I pulled the LS00 out and got the memory error screen again. So, Something is amiss. I'm bought a decent bunch of ICs so I'll swap everything out that I got and see if that works later tonight.
Did you remove all the chips up to the smoke test 4 right ?
I did that before and still got a black screen with keeping LS00 and removing the SRAM chip.
I removed all of the Smoke Test 4 ICs and got the memory error screen, which is correct for Smoke Test 3. I still get the memory error screen if I keep all the ICs in except LS00. Pull LS00 out and I get memory error; put it back in, then it's a black screen. Swapped LS00 chip from Mouser, same result. Weird. Solder looks good as do traces.
Alright, update to Omega Build. I swapped all the ICs from my order to the board. Swapping one by one to see what changes I could see. It was all black screen till I swapped the U31. No bios screen, but I did get a Blue Screen. No text or anything. Just a blue screen. I kept swapping the remaining and everything is basically HC/HCT ICs except U23. Mouser didn't have that in stock, but I didn't look for a similar item either. But anyways, could that chip cause the blue screen or can something else now be the cause? Almost all the ICs are new now.
That's what MSXMakers said, but they could still work; it's just unknown in what combination they seem to work or what breaks their compatibility in this build. So yeah, i could find a similar and replace, but the end question is if that can cause a blue screen or if another IC could be at fault here with such a result?
You really should use LS components or if you want CMOS then HCT (but characteristics may not be identical between LS and HCT versions).
They were all LS ICs from the China eBay order. Nothing but problems. Original BOM states HCT and no LS recommended BOM, so for replacements, I just ordered what was in the BOM. I'm just trying to get feedback on what could cause a blue screen on Smoke Test 4 with everything basically being a 1:1 match to the BOM on the logic ICs except U23.
I know U2 IC is a replacement, but the one in the BOM is sold out everywhere and eBay is my last choice, but would prefer to stick to Digikey/Mouser or some other reputable shop in the US.
Well, I'm about at my wits end here. Currently asking a friend about a scope but I don't know how to use it. I've swapped the last LS IC with an HCT and the same result on Smoke Test 4. Remove an IC and I get memory error. I've reflowed about half the board and isn't changing the results.
I've gotten a black screen with a signal, blue screen with nothing on it, and even a few Gray screens. The gray screen is new, but only got it twice and haven't again. Does any of this point to a potential IC issue? VDP? CXA? 8255 PPI? something?
