Jaguar occasionally works - need help

[Shakes]

So I have a Jaguar that looks new inside and out. It powers up, but the dreaded black screen. Occasionally, it will show the Jaguar loading screen, and sometimes completely loads the game. It will freeze at the boot logo without sound most times it does boot. It does work 1 out of 100 boots and plays fine when it does, so I know T&J are fine. I have played 3-4 hours without issue. If I turn it off though, this starts the cycle all over again...

 

Troubleshooting so far:

• Checked the power capacitors
• Cleaned the cartridge connector, which had pins that were a little stretched, but swapped it out just in case
• Cleaned the power switch, but swapped it out to test as well
• Tried multiple games (Cybermorph was still in the original unopened plastic), same results
• Tried OEM psu and Genesis model 1 psu, same results
• Tested RF modulator and composite soldered to the board, same results

 

I'm at a loss on where to look next. Unfortunately, I don't have a scope just a DMM, nor a second Jaguar to help troubleshoot, and am hoping someone here has experienced this before. The board is super clean as you can see, no corrosion or anything that's seen in my microscope either. I don't know what would allow the system to boot completely every 100 times, but only load the Jaguar screen maybe once every 20 times. Generally, if I hear the roar when I turn it on, it will completely boot. No roar, it will have no sound and perform the loading animation and freeze after the ATARI drops.

[Jaguar 2000]

wow look at that thing! all those chips and circuitry and we had to settle for flip out, zoop and dino dudes.

?

other than blasting electrical cleaning spray - i have no other tips. my genesis used to freeze up too- but since i cleaned it out- never had any issue. 
but that circuit board looks pretty good. don't know why it won't work properly.

[Zerosquare]

That won't help you much, but I had a Jaguar with the same symptoms (except it usually booted successfully). I replaced the capacitors in the power supply section and checked the clock using a scope. Despite spending several hours on it, I couldn't figure out what was wrong.

[Wilco]

I would say it’s probably bad luck, I’ve had that more than often with old broken consoles.
 

I would definitely try replacing the capacitors even if they look fine, if that doesn’t solve it I truly wouldn’t know. 

 

You could maybe try contacting best electronics as they do Jag cd repairs. But I don’t know if they can help with base consoles. 

[Shakes]

21 hours ago, Zerosquare said:

That won't help you much, but I had a Jaguar with the same symptoms (except it usually booted successfully). I replaced the capacitors in the power supply section and checked the clock using a scope. Despite spending several hours on it, I couldn't figure out what was wrong.

The LED lights bright each time, but I also replaced the two large power capacitors, C174, and C142 on the power side to check. No change. Checked all the others capacitance levels and they all are within spec. 

 

I hate not knowing what's going on with this thing, as I've spent many hours scouring the forums looking for solutions with little to show for it. The best I can come up with such a random issue is a dynamic component failure, but I've swapped the cart connector, switch, and RF modulator, all with the same results. 

[JagChris]

You swapped the entire cart connector? How hard was that?

[+cubanismo]

Any chance there's a cracked solder joint somewhere?  Seems like that might explain such intermittent behavior, given pressing a cart in or warming it up a bit from repeated attempts might flex things just enough for it to make contact.  Just a wild theory though, and no idea how to track such things down.

[Shakes]

1 hour ago, JagChris said:

You swapped the entire cart connector? How hard was that?

Without the right tools? A nightmare and you will probably damage the board. With them, not difficult, but the right tools aren't cheap unfortunately. The ground plane on these boards is huge, so it takes some real heat to get this board up to the right temp to start, and there's like 10 ground pins in that connector.

 

 

56 minutes ago, cubanismo said:

Any chance there's a cracked solder joint somewhere?  Seems like that might explain such intermittent behavior, given pressing a cart in or warming it up a bit from repeated attempts might flex things just enough for it to make contact.  Just a wild theory though, and no idea how to track such things down.

I wouldn't rule it out, but I've inspected it pretty thoroughly and can't find anything. There was a few that were suspect, and if you look closely at the bottom picture of the board, you can see where I reflowed some joints outside of the aforementioned spots. I had a similar thought, which is why I turned to the dynamic components, but even after playing it for hours, as soon as you turn it off and on again, it could take a full 100 tries before it worked successfully again. So odd. I'd rather it never worked then worked the way it does, as that would explain more than such intermittent behavior.

 

Appreciate everyone's ideas. Adds perspective I may not have thought of. Cheers!

[RodLightning]

Component cooler spray is handy to identify a flakey IC or cap or transistor.  Not sure if the stuff can be easily obtained anymore.  Sometimes a quick burst of cold will bring a failing part back into spec, or push one that has warmed up enough to work, into failure.   A meatball approach for sure, but it can sometimes give you a clue.

 

[+cubanismo]

1 hour ago, Shakes said:

I'd rather it never worked then worked the way it does

Indeed, these are the worst kind of bugs:  Tantalizingly close to working, but not quite usable as-is, and ridiculously hard to diagnose.  This is why I generally oppose useless error handling/checks in software: I'd rather have it just assert/abort or segfault and catch it in the debugger than have it almost-sorta work but have some random weird side effect because some never-tested error path was executed.

[+Stephen Moss]

On 9/5/2020 at 2:20 PM, Shakes said:

So I have a Jaguar that looks new inside and out. It powers up, but the dreaded black screen. Occasionally, it will show the Jaguar loading screen, and sometimes completely loads the game. It will freeze at the boot logo without sound most times it does boot

A black screen with a lit power LED rather than the Red Screen of Death suggest that it may be getting as far as passing the cartridge checksum test.

Are you getting a good 5V supply from the main power regulator when it is misbehaving? 

[Shakes]

On 9/7/2020 at 4:18 AM, Stephen Moss said:

A black screen with a lit power LED rather than the Red Screen of Death suggest that it may be getting as far as passing the cartridge checksum test.

Are you getting a good 5V supply from the main power regulator when it is misbehaving? 

Yes, the 5V is present on the appropriate pins of both U38 and REG1. I don't think this is a power issue as the unit powers on each time. I'm more inclined to think it's audio or video related as that seems to be the oddest of the behaviors. Like I mentioned, it will work eventually, but may take 100 tries. The other weird thing is about 5 of those 100 there is video, but no audio, but that doesn't get passed the boot screen. Meaning, no roar, no letter falling sound, then freeze. 

 

I played it last night without the shell and bumped Tom & Jerry, the RF modulator, and all the other chips to test for any loose or cold solder joints. Game stayed running without a hitch. I'm wondering if one of the crystals are failing, but I don't know what that behavior would look like.

[eightbit]

You've done so much to the board thus far (congrats on the cart connector replacement...I wish I had the tools to do that!) and you may have hit the nail on the head regarding the crystals. Why not just go ahead and replace them? Best has them and they are relatively inexpensive:

 

http://www.best-electronics-ca.com/custom-i.htm

[+af0l]

On 9/6/2020 at 9:50 PM, JagChris said:

You swapped the entire cart connector? How hard was that?

Not that hard at all. 

[+af0l]

I just had a similar issue with a friends Lynx 2. He asked me to recap it and the issue got worse. It was working, but no video was comming out. In an act of despair, I fluxed the damn thing and reflowed about a third of the board. Works without a glitch now. ?