Problems with Attack of the PETSCII Robots

[+cvga]

I just found this thread but it reminds me of the time I bought Bentley Bear and had issues with my slightly modded 7800. It runs fine on my unmodded 7800 though. 

[prorok]

2 hours ago, Mitch said:

That is normal for Tower Toppler. Check your difficulty switches.

 

Mitch

Thanks, Mitch.

 

The embarrassing truth is that I even have the manual for Tower Toppler. Maybe I should actually read it some time! 🙂

[prorok]

Debugging continues...

 

I purchased another 7800. This one appears to be entirely stock, though I haven't opened it up yet to verify, and PETSCII Robots runs just fine on it. With one working and one non-working console, as time permits, I can start running increasingly invasive experiments to see if the problem moves with component swaps.

[+-^CrossBow^-]

7 minutes ago, prorok said:

Debugging continues...

 

I purchased another 7800. This one appears to be entirely stock, though I haven't opened it up yet to verify, and PETSCII Robots runs just fine on it. With one working and one non-working console, as time permits, I can start running increasingly invasive experiments to see if the problem moves with component swaps.

Note which CPU is present in each one as far as the brand of CPU. Also any other differences as well in the component layouts or stuff being present on one that might not be on the other...etc.

 

[+cvga]

I found the email from when I had my lightly modded 7800 fixed...

 

It's done!  I cleaned up it a little as far as the mod is concerned.  I put it on a PCB and mounted it to the motherboard and changed all the wiring to be color coated and solid copper vs stranded.  Not that it wasn't right before, but there was opportunity of something to get jostled on its way back and a wayward wire create some short (I also like it to look clean:)).  Also, in the picture where the red box is over a wire, I added that wire as it adds in POKEY sound for games that use it.  Tested it with both TIA (Robotron 2084) and POKEY (Ballblazer) sound and they're both working.  The red port I added is just a little bit off on measurement.  I thought that I got it right, but I was just a bit off, it's close though.  I'll get it boxed up and sent back next week.

 

 

I'll bet yours is the same issue. Evidently some early mod kits didn't include that last step since Pokey chips weren't highly used at the time.

[+-^CrossBow^-]

10 hours ago, cvga said:

I found the email from when I had my lightly modded 7800 fixed...

 

It's done!  I cleaned up it a little as far as the mod is concerned.  I put it on a PCB and mounted it to the motherboard and changed all the wiring to be color coated and solid copper vs stranded.  Not that it wasn't right before, but there was opportunity of something to get jostled on its way back and a wayward wire create some short (I also like it to look clean:)).  Also, in the picture where the red box is over a wire, I added that wire as it adds in POKEY sound for games that use it.  Tested it with both TIA (Robotron 2084) and POKEY (Ballblazer) sound and they're both working.  The red port I added is just a little bit off on measurement.  I thought that I got it right, but I was just a bit off, it's close though.  I'll get it boxed up and sent back next week.

 

 

I'll bet yours is the same issue. Evidently some early mod kits didn't include that last step since Pokey chips weren't highly used at the time.

The problem with audio is where you are getting the TIA audio from. You are taking it directly off the IC legs as I can see in that picture. The problem is that it is before the resistors and not after as is needed for proper balance between the TIA and POKEY. What you have in this picture will work for actual cartridges without issue. But if you use a concerto or some of the newer homebrews that use HOKEYs in them, you are likely to run into issues with still not being able to hear the POKEY/HOKEY audio properly.

 

The audio signals need to be taken from north ends of R5 and R6 next to the audio adjust coil.