Found this possible modification to my Genesis...

[brentonius]

Hey everyone. I opened up my "High Definition Graphics" (haha!) model Genesis for the first time today to do a little cleaning and see what capacitors I might need to grab for a cap exchange. It appears that someone has tinkered around with it before... It has some weird blue glue around certain screws which I had to chip away. One screw couldn't come out at all, so I had to tear it off. All in all, I was able to undo all the screws. But here's something interesting that I found. A few wires have been soldered into the board. Not quite sure what this is accomplishing, or why it was done. Anyone know or wanna make a guess?

[ApolloBoy]

None of those are mods, those jumper wires and the blue glue were added at the factory.

[7800fan]

Probably bug fixes. Sega service manual mentions a few mods that are required because of design variation that can cause problem. For example, a certain model of Genesis might not want to work with Sega CD properly. And certain model also have problem with 32X and no CD attached, etc.

[Osgeld]

yea its fairly common to find jumper wires in early revisions of electronics from back in the day.

 

now days you just spin a new board and maybe a week later if you have time and are being cheap you get a new revision to debug (I did a pcb revision and had 600 14 up pannels in 3 days shipped just this week ... want cheap) , back in the olden times, you had all this crap hard wired on perfboard and wirewrap, based on your schematic, then pcb artwork was done, when you were comfortable you started off a few months worth of production

 

Then once the boards come in you have an Oh crap moment, there's a mistake or something was missed!!, what do you do, bite the bullet and have a few workers add jumper wires teween test points and via's, or halt a years worth of production boards with 3-6 months in the pipeline while you make a change, and then have to renegotiate price with a pcb vendor, retaillers, management, parts vendors, etc that doesnt take you seriously cause you jerked them around?

Edited June 11, 2016 by Osgeld

[brentonius]

Interesting! Curious... I wonder if people / factory workers made this modification or if it was done by a machine. Looking at it, it seems people.

 

Also, I have another question. Kind of related... but in so many consoles I open (and I have opened a great many up) plus game carts I have noticed that often a chip will have a yellow, red, or blue chalk mark across it. Does anyone know why some of these were "chalked" and what it means?

[Osgeld]

typically that means a programmable chip was programmed

 

or maybe there was a quality issue with the supplier and those were marked to show they were looked at and verified

 

or maybe its an internal factory thing, like at some stage of the process someone looked at it and checked off their part of the board

 

who knows

[towmater]

If you follow each wire you'll see that the pads they are soldered to are labeled identically on each end, so it was definitely meant to be done from an early stage in design.