Jaguar Crashing - checked all the usual

[Beeblebrox]

I have recently acquired a 2nd Jaguar which was bought from a seller advertising it as not working/powering up. I am lead to believe it was in storage for a long time, (a good number of years), but I understand he'd powered it up in the last few months and played games with no issues until recently when he had recently gone to use it of late and it just didn't power up.

 

Whne I received it it din;t power up at all but not really surprising as very dirty and the issue was clearly the cart bay contacts were dirty, as were the carts it came with.

 

I cleaned it up and sure enough it powered up, gave me the Jaguar animation. Joy was short lived though as it was very evident that there is an issue with it crashing very early on with games. Not the red screen of death, but as documented by other owners it crashes at the same points part way though the starting title menus or, in the case of one game, after playing for while.

 

I get sound and video so it would appear the power regulator chip (U38) and REG1 chip are both ok, and at least one game plays for a while, (Zool allowed me to play the first level with no issues, where it crashed after completing said level and gave me a black screen.)

 

Basically with DOOM, Cannon Fodder and Wolf3D the games crash at the very early menu stages after the graphics glitch, and sounds go crazy. It's always at the same stages.

 

When I first encountered this I immediately checked the temperature of the main chips and also some of the smaller ICs. They are all fine and only slightly warm at the point of crashing with DOOM, Wolf3D and Cannon Fodder. And when I played the first level of Zool (5mins play), only then do the 3 x main chips get hot, (most notably the main CPU and graphics chip and also the DSP), but I am assuming this is to be expected anyway after 5 mins of play given what they do, their clock rates, no heatsinks or fans being used, etc(?)

 

The fact Zool plays for a whole level makes me wonder if there is a bad memory chip issue.

 

I have checked and cleaned all the Jag's cartridge bay contacts and have another fully working Jaguar available where I've tested all the game carts and they work flawlessly on that. I cleaned the carts anyway of course - but we can rule out the carts as the issue.

 

I have also checked the continuity of the cart connector bay pins with the PCB pins underneath and that is all fine. Plus checked and no bent or misaligned pins.

 

There is no trace corrosion, oxidisation or noticable breaks in traces. All caps look fine. I am using a stock Atar Jaguar PSU which works fine with my other Jaguar.

 

The U35 IC (the BIOS chip I believe) , had some notable oxidisation on pins 1 and 2 but I checked out the continuity on these where they connect with the PCB and all related solder points and traces and even touching up the Bios chip's pins with some solder hasn't improved the issues. (After the solder work I checked again for continuty and that I'd not bridged anything BTW).  Powering up and the same issue persits.

 

I am a big Atari 8-Bit fan and owner of many Atari 8-bit computers an as such have a good amount of knowhow in that respect when it comes to soldering, (having fixed a good few Atari XLs and XEs). When it comes to the Jaguar I have experience with replacing the blown U38 SMD power regulator chip and a couple of related Caps on another Jaguar.

 

Anyone have ant ideas how I might start to get to the bottom of this? I saw another AA post where someone replaced the Bios chip but their issue was a broken trace undernearth the BIOS chip and their Jaguar wasn't giving any video or sound output at all. Can a bad bios chip cause the issues I am describing? If so where can I source a new chip? 

 

If this is more likely a bad RAM chip does this sound like a memory issue given the fact that Zool plays fine up until the transistion between completing the first level and interim menus? I don't think the issue relates to any of the main processors.

 

Thanks in advance for any hints or tips.

 

Here are some images of the crashes in said games:

 

So I get the normal Jaguar intro animation with all games no probs, with the spining textured cube and the sampled Jaguar roar, etc (animated letters are all fine):

 

and DOOM's title menu as well as Cannon Fodder's is initially fine:

 

    

 

 

Then if you try to progress and/or leave the games to run their demo modes (as in the case of DOOM), you get glitching and crashes:

    

 

 

[Zerosquare]

If you have a way to run ROMs on your Jaguar, try the diagnostic program here:

 

[Beeblebrox]

@Zerosquare  Many thanks for the thread link, much appreciated.  Unfortunately at present I don't have a way to run ROMs. I was looking into getting the Jaguar Game drive at some stage when I can drum up the cash. (£170).

 

In the interim I wonder if there are any other experiences/insights from Jag owners who've had this issue or similar?

 

I have a replacement U38 power regulator on it's way which I think I am gonna install anyway just in case the current one has something to do with the issue. They are dirt cheap and it can't hurt. (As I say I've experience with doing this on another Jaguar I fixed as mentioned in the first post).