Joust ROM Board issue

just replace the Special Chip sockets. I don't know the logistics of what pin does what, I just know when the game text looks like Standard Galactic Alphabet that's a connectivity issue at the Special Chips.

I could be wrong but it seems that's the one thing that hasn't been tried yet.
 
You are :) See first post "Replaced the 2 sockets on the customs"
I don't dwell on the dozens of threads I post in. it's been a long time since I've handled one of those rom boards. it may be a fault in another chip in circuit. I don't generally see those go bad except the 4049 which can prevent the game from loading at all. if I have a chance I'll look at schematics.
 
Is it worth checking the Bay for another ROM board? Or posting a WTB ad here at KLOV? Change the scenario.
 
Is it worth checking the Bay for another ROM board? Or posting a WTB ad here at KLOV? Change the scenario.

This is entirely non urgent. There is absolutely no need to randomly tag people or to go buy a replacement.

I'll fix it. I started the thread to document progress. Now it's booting to a clean 0 it should be easier.
 
so looking schematics over, there's the 74LS244 (9C, also cited as IC1 because some Robotron rom boards had the little riser board that added the resistor pack) ... you didn't post pictures of the rom board(s) in question so maybe you have that or not. otherwise those parts are just installed in the rom board itself. I have a couple of those that don't work and I wonder if the resistor packs got broken on them. there's some Special Chip faults I've seen that can cause 1-3-1 (0-3-1 on Sinistar) errors, I found these back in 2015 and chip reseats fixed them then and I've never seen it again in 100 some boards since. the 244 is for the address lines to the Special Chips. there's also the 74LS245 (8C) for the other half of the address lines. the data lines to the Special Chips just come off the MPU via the ribbon cable -- if anything were wrong there the game just wouldn't load at all. I'm spitballing here, it's not something I've ever seen before that I've fixed.

the WINHU and WINHL from the Special Chips I just realized are directly tied to the 7410 chips at 4M and 4L, which are for the upper (rams 5-8) and lower (rams 1-4) write enable functions. I suppose I answered my question as to the origin of the 1-3-1 errors these can produce. lol

for giggles you should be able to measure continuity at each pin between the Special Chips to see if you have a bad solder connection somewhere.

I've been borrowing one of those Backbit chip testers from a guy I know local, that would've made my life a lot easier when I was fixing these years ago. I hope this is helpful in getting you on the right track. I've fixed so many games outside of these I genuinely can't remember anymore if I've fixed this, I think I only had bad sockets in the past.

also @braedel if you know anything deeper you should make a video about it in the interest of science.
 
you didn't post pictures of the rom board(s) in question so maybe you have that or not. otherwise those parts are just installed in the rom board itself. I have a couple of those that don't work and I wonder if the resistor packs got broken on them

I did post a video though :) All joking aside I have a third ROM board (very non-working) that has this riser board. I was curious what it was for. I see now where the SIP pack is on the later boards just below one of the specials. Thanks for the info! I'll ohm them out. I've not spent any time looking at it for a couple days.
 
Back
Top Bottom