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mysterious Jaguar hardware mod

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Hello, every one. I picked up a Jaguar recently that needed some repairs, but when I opened it up I discovered that it was modded at some point. While searching across the net I found an image of some one else's Jaguar with the exact same modifications. [ portion of that image attached below ]

 

Has any one seen this mod before? I have no idea what it does, nor if it was completed. haha

 

Are the two orange things tiny capacitors? (on the U23 chip on the right-hand side)

Mine have 6 characters inscribed on them. It's too tiny for me to read, but it seems to be some thing like:

 

n2n

101

 

post-35391-0-20155700-1365381491_thumb.jpg

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I think this is a factory change, probably done to improve board yield. Those orange parts are capacitors, and they look to be taking two of the DRAM signal lines to ground, probably as a way to reduce ringing and make the signals more reliable. The blue wire is from a test point to the power input on that chip, and maybe helps provide extra power needed after the PC board layout was found to not work as well as planned.

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I've opened a few Jaguars, and not seen mods like these. Interesting that you've found other people online with the same mods!

 

Both mods were added to improve the stability of the console. The wire from U11 to TP3 increases the strength/slew rate of the master 26.6MHz clock, which might help if timing was marginal.

 

Those capacitors were added to help stabilize that particular RAM chip. In a way, the mods are related. The extra wire may improve timing, but it will add noise that might require extra capacitors to dampen.

 

It's likely that some Jaguars failed a certain factory test, and these mods are the prescribed fix.

 

- KS

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1st subject for me ... so hello everyone First of all, sorry for English, half school, half Google ... I just received my Jaguar. A childhood dream. I bought it knowing a concern that I submit to you. She starts when she wants ... 10 to 20 trials. Nothing. The green LED lights up. The TV seems to be receiving a signal. But black screen. Then suddenly. It works. Cybermorph's 3d did not make my 10 year old son tripple, but I did. 2 hours of games ok. I switch off. Then, the time to type this subject, it does not work anymore ... The food is original. The scart cable was purchased here https://coolnovelties.co.uk/coolnovelties/atari-jaguar-video-cables/35-atari-jaguar-rgb-scart-cable-070569350471.html

Another TV tried. Same

Another game tried. Same

Power cable tested. OK, anyway, the indicator (green) lights up...

I dismantled the hood and ... surprise. I come across a not trivial version. It looks like 2 drops of water like this.

Mine here https://www.zupimages.net/viewer.php?id=20/05/d3qj.jpg

Couldthere be a link with my concerns ??? I seem to have found a tactic, if you can say, to get it started ...

Could it have something to do with the video cable? I am a little lost... Thank you for your help !!!

Edited by pkerga

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Maybe also look at the power switch, they are pretty cheap to replace and it will take that out of the equation when tracking down the problem. 

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Console5 is an excellent business to work with! I pretty much buy all of my capacitor kits from them along with other components.

 

 

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Hi
 While waiting for the arrival of the capacitors (which are at Roissy ...), I took a look at the motherboard.
 I have the impression that there has already been some work.
https://zupimages.net/viewer.php?id=20/08/578u.jpg
https://zupimages.net/viewer.php?id=20/08/mxsu.jpg
https://zupimages.net/viewer.php?id=20/08/dzml.jpg
https://zupimages.net/viewer.php?id=20/08/9a7d.jpg

 

 

Is the area circled in red normal ???


https://zupimages.net/viewer.php?id=20/08/ls61.jpg

Edited by pkerga

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The part in red is normal. Those are grounding tabs that were soldered onto the mainboard so that it would ground properly against the bottom RF shield. Not too many consoles did this but I've seen it on other electronic devices over the years.

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Sorry for my google translation...

 

1 1/2 months and a pandemic later ...
I sent my console to https://www.otakus-store.net
Conclusions:
"It seems that the large ripple generated by the switching regulator creates random oscillations (I did not identify on which component precisely), causing in passing an overconsumption in current of 30%, therefore probably overheating somewhere. ..
I modified the 5VD power circuit to fix this. There is no problem anymore. "
Back this day from the console that purrs like on the 1st day!

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53 minutes ago, pkerga said:

Sorry for my google translation...

 

1 1/2 months and a pandemic later ...
I sent my console to https://www.otakus-store.net
Conclusions:
"It seems that the large ripple generated by the switching regulator creates random oscillations (I did not identify on which component precisely), causing in passing an overconsumption in current of 30%, therefore probably overheating somewhere. ..
I modified the 5VD power circuit to fix this. There is no problem anymore. "
Back this day from the console that purrs like on the 1st day!

 

That is great! In case you did not know, this site sells some really great Homebrew games for the Jaguar.

 

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