Atari Jaguar BJL troubleshooting

[jaywalk101]

Hey guys.  I'm hoping someone here can help me.  I'm trying to fix a jaguar with no image or sound.  The thing is I can boot from BJL bios.  When I load a game (Tempest 2000 for eg), it will work for a minute and then crash back to BJL main screen.  I get the attached error.  Any ideas?  I'm leading towards failing voltage regulator, or faulty RAM.  When using stock bios, I get no screen or audio. It just turns into a white fuzzy screen after 20-30 seconds.  Thanks in advance for any suggestions.  

 

 

[LinkoVitch]

Err 4 (assuming that is 68K) is Illegal instruction.  Either it's hit an "illegal" or hit some garbage in ram when executing.  The rest of the values are Program counters and 68000 Register dumps. 

 

When you try with official BIOS do you get a red screen on boot? or does the game also start and then crash out?  IIRC BJL doesn't verify the whole cart like the official BIOS if you boot a cart from it, so it's possible to have a bad cart contact and the game crash when it needs to use that pin.

Do the games included with BJL work OK?

 

[jaywalk101]

22 minutes ago, LinkoVitch said:

Err 4 (assuming that is 68K) is Illegal instruction.  Either it's hit an "illegal" or hit some garbage in ram when executing.  The rest of the values are Program counters and 68000 Register dumps. 

 

When you try with official BIOS do you get a red screen on boot? or does the game also start and then crash out?  IIRC BJL doesn't verify the whole cart like the official BIOS if you boot a cart from it, so it's possible to have a bad cart contact and the game crash when it needs to use that pin.

Do the games included with BJL work OK?

 

Thanks for the reply!   In the official bios I get nothing. Just a blank screen and no audio.  Then the screen eventually goes to a fuzzy white.  I've ruled the carts out as I jumpered pins to power on without the cart and I get the same thing. Kind of strange.  No. As for the BJL games.  How do I load them?  I don't see any options. Thanks!

[+cubanismo]

If you're using the BJL image I just did, the games aren't there AFAICT.  It's only ~11k and seems to just include the loader.  However, as you can see in the screenshot, you can press B to boot the cartridge.  Would be interesting to know if that works.

[jaywalk101]

I can load the cart by pressing b. It will start playing a retail game anywhere from 3-30 seconds and then restart back to the BJL menu.   Im leaning towards it being a failing u38 chip, or faulty memory.  I'm going to try to reflow all the memory chips later.  I'll also try to replace u38 for good measure. If that doesn't fix it I'll probably have to put it on flea bay.  

[jaywalk101]

Found out something else weird. When I load tempest 2000 from the cart in BJL, if I disable the music from the gamepad, the game works fine.  As soon as I enable music, it crashes back to main BJL screen with attached pic in first post.  Sound effects still work as well.  

[LinkoVitch]

I'd not suspect it's the RAM, the OP makes 64 bit reads from the RAM, so all 4 chips are being used whenever you see something on screen.  Of course there could possibly be a single pin/track gone/going bad somewhere, I'd just suspect bad ram as having a more instant effect.  Bad power isn't going to help, so deffo look at that, perhaps dried out cap in the power chain ?

 

[jaywalk101]

It indeed was the RAM. I bought another jaguar for parts on eBay. It was corroded pretty bad.  Took the ram off that jaguar and soldered it in and it's working like a champ!