Inferno assistance.

jkoolpe

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Hey all!

Well, my Inferno went dark at CAX :( . I've never had an issue with it before, but it went out sometime in the later morning of Saturday while at the show. Another KLOV'r and I did our best to try to bring it back to life, but with our limited resources at the show, we were not successful. Bummer as I had recently refurbished the joysticks which were now very tight and responsive so I was looking forward to folks enjoying the game even more this year. Believe it or not, I've taken it to CAX for 16 years now!

Anyway, it's now stuck on the ROM boot up screen, and the LED on the CPU board is completely dark and shows nothing.

So far, I've tried:

1) Testing voltages...all good, game is running off of a switcher that was installed by the previous owner
2) Replaced CPU chip
3) Swapped in 2 other Special Chips from an extra Joust 2 boardset
4) Tried 2 new 6116 RAM
5) Reseated chips

None of the above has done anything.

Aforementioned KLOVr did some logic probing at the show and found some floating lines so I replaced the logic chips that seemed to perhaps be unhappy. In this case, these were IC 62 (74LS245) AND IC39 (74LS244). Still nothing.

Now that the game is back home, I've now been able to set up my o-scope such that I can probe the Inferno board and the Joust 2 board running in each of their respective cabinets (using Channel 1 and 2, respectively) which just happen to be sitting next to each other in my garage/arcade (which was fortuitous :) ) .

I did some preliminary probing and comparisons earlier tonight, and I don't seem to be seeing any activity at the inputs of IC68 (74154 chip) which I *think* is being fed to by both IC 39 and also IC 42 so I am thinking to also try replacing the latter. And the 74154 chip does seem to control a lot of the inputs to the ROM chips (many of which show no activity...at least for several that I probed).

Forgive my amateur reading of the schematics (I'm using the Joust 2 ones that were recently spruced up by another KLOVr to make them much more readable and uploaded to KLOV), but certainly if anyone else out there with a better ability to read schematics and/or might have other suggestions for me, that would be most appreciated.

Thanks,

Jonathan
 
I feel very fortunate to have briefly played it while it was up and running on Saturday! Wishing you the best of luck in getting Inferno back online soon.
 
Hey all!

Well, my Inferno went dark at CAX :( . I've never had an issue with it before, but it went out sometime in the later morning of Saturday while at the show. Another KLOV'r and I did our best to try to bring it back to life, but with our limited resources at the show, we were not successful. Bummer as I had recently refurbished the joysticks which were now very tight and responsive so I was looking forward to folks enjoying the game even more this year. Believe it or not, I've taken it to CAX for 16 years now!

Anyway, it's now stuck on the ROM boot up screen, and the LED on the CPU board is completely dark and shows nothing.

So far, I've tried:

1) Testing voltages...all good, game is running off of a switcher that was installed by the previous owner
2) Replaced CPU chip
3) Swapped in 2 other Special Chips from an extra Joust 2 boardset
4) Tried 2 new 6116 RAM
5) Reseated chips

None of the above has done anything.

Aforementioned KLOVr did some logic probing at the show and found some floating lines so I replaced the logic chips that seemed to perhaps be unhappy. In this case, these were IC 62 (74LS245) AND IC39 (74LS244). Still nothing.

Now that the game is back home, I've now been able to set up my o-scope such that I can probe the Inferno board and the Joust 2 board running in each of their respective cabinets (using Channel 1 and 2, respectively) which just happen to be sitting next to each other in my garage/arcade (which was fortuitous :) ) .

I did some preliminary probing and comparisons earlier tonight, and I don't seem to be seeing any activity at the inputs of IC68 (74154 chip) which I *think* is being fed to by both IC 39 and also IC 42 so I am thinking to also try replacing the latter. And the 74154 chip does seem to control a lot of the inputs to the ROM chips (many of which show no activity...at least for several that I probed).

Forgive my amateur reading of the schematics (I'm using the Joust 2 ones that were recently spruced up by another KLOVr to make them much more readable and uploaded to KLOV), but certainly if anyone else out there with a better ability to read schematics and/or might have other suggestions for me, that would be most appreciated.

Thanks,

Jonathan
oh yeah, 74154 is the chip enable for the roms. that'll render them not working if it isn't firing. IC56 74LS75 is a quad latch, was that your target?

I forgot all about the new schematics, I had them saved.

I wish I could get a crack at this but I really don't want to work on games at all in my off time anymore. and like I told you earlier @braedel has logged more hours with the newer gen hardware than me. maybe we can talk it over on the phone Friday or Saturday.
 
I did some preliminary probing and comparisons earlier tonight, and I don't seem to be seeing any activity at the inputs of IC68 (74154 chip) which I *think* is being fed to by both IC 39 and also IC 42 so I am thinking to also try replacing the latter. And the 74154 chip does seem to control a lot of the inputs to the ROM chips (many of which show no activity...at least for several that I probed).

Probably a red herring. The '154 only controls the banked ROMs, and you're probably not getting far enough into self-test to ROM check or run any code in the banked region.
 
On the CAX floor it was determined that A15 was stuck high. I would suspect this activity is atypical but don't know the hardware well.

Swapped CPU, no change

Pulled one SC at a time, and later they were both replaced, no change

Cut the input pin (11) at IC39 (LS244), no change

I suspect this A15 behavior should be where to focus.

Also found that all outputs at IC62 (LS245) are floating on the logic probe but suspect this is due to the enable and also traces back to A15
 
The address lines all have 4.7k pull-up resistors on them. I would expect A15 to always be high except when the CPU drives it low.

1753496245463.png

~Brad
 
@braedel is it odd that all other address lines are toggling away except A15?

and, going back to the 245 at IC62, all outputs are floating and Jon swapped the chip to no change. Considering the 245's above and below that chip (IC61 and IC63) are operating fine it seems suspect.
 
Did some comparisons tonight, and found that the 74LS00 at position 2F (IC32) seems to be getting input at pin 11 and outputting at pin 12, but no output at pin 13. Schematic says it should output from both p12 and p13. p13 on the Joust 2 game is outputting for sure.

Am I onto something? Should I try swapping out this chip?

Again, please forgive my amateur skills here :) .

Jon
 
Did some comparisons tonight, and found that the 74LS00 at position 2F (IC32) seems to be getting input at pin 11 and outputting at pin 12, but no output at pin 13. Schematic says it should output from both p12 and p13. p13 on the Joust 2 game is outputting for sure.

Am I onto something? Should I try swapping out this chip?

Again, please forgive my amateur skills here :) .

Jon
I found it on the sheet. I think you're onto something.
 
You're right!

OK, I backtracked from 2F, pin 13 through the other input pin on 2F (pin 10), pin 8 and 9 on 3F all the way back to the MPU chip and found no activity on pins 5 and 6 which are labeled as outputting (?) "BA" and "BS" as well as pin 40 (the "HALT" signal with the overscore which I think means it should be an active low signal?) which is I think as it should be for this pin.

So even though we had already swapped in a another 6809 at CAX, I tried that again with another new 6809 and still nothing.

Did some research and it looks like "BA" and "BS" are "Bus available" and "Bus status" which might just mean that since the game logic is not running, that I would expect these to be dead lines.

So now I'm a bit stumped as to where to try to probe next.

Jon
 
The BA/BS and Halt are only used when the 'Special Chips' aka Blitters take over the busses. I wouldn't expect activity on these until the game code is running (passing all the self tests for RAM/ROM)

When the game wants the Blitters to move a bunch of data(ROM to RAM, RAM to RAM, Shift Right, etc), the CPU sends the command with instructions to the Blitters, then triggers the BA. At this point the Blitter will trigger HALT and the CPU stops executing all instructions. When the Blitters are done, they release the HALT and the CPU takes over again, exactly where it was.

~Brad
 
So at least I was right about not expecting these lines to be active given the game's current status of being dead.

So much for my first attempt at trying to figure this one out :( .

So where to probe next? Maybe the outputs for all of the 74LS chips shown in the upper portion of the page 2 of the CPU schematics (above the Address Bus 4 line) which appear to lead into the 6116 RAM chips?
 
Probed a bunch more chips this afternoon, and found that pin 6 of IC36 (a 74LS74 chip at location 1F) appeared to be getting its inputs but not outputting any signal at pin 6 but was doing so on the Joust 2 board. Tried replacing it with a new chip, but no change.

Will keep at it...

Jon
 
Probed a bunch more chips this afternoon, and found that pin 6 of IC36 (a 74LS74 chip at location 1F) appeared to be getting its inputs but not outputting any signal at pin 6 but was doing so on the Joust 2 board. Tried replacing it with a new chip, but no change.

Will keep at it...

Jon
Do you have a logic analyser? Even a cheap one? Even if all the inputs on the ls74 are toggling, they might not be at the right times to produce an output. A logic analyzer will help you to figure that out without pulling the chips.
 
I have a cheap logic probe, and also an HP Logic Comparator. The latter is useful certainly for analyzing chips while they're still on the board, but they have to be either 14 or 16 pin only (which fortunately is true for most of the 74LS chips). I did use it for some of the chips I changed out and it said they were OK, but sometimes I don't fully trust it so I still changed the chips...I guess I should have trusted it :) .

But I've mostly been using my o-scope and making comparisons between the Inferno and Joust 2 while both boards are powered up in their respective cabinets.

Jon
 
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