Mega Drive 50/60Hz switch NO LONGER working!

[FM-77]

I have the oddest problem with my PAL Mega Drive II. A few months ago I modded it (installed a 50/60Hz switch and a Jap/Eng one). I used this guide.

Playing it 50 and 60Hz worked perfectly with the switch. No problems at all.

However, recently the switch completely stopped working. Can't switch over to 60Hz. I thought one of the cables might have been faulty so I replaced them. No luck.

Then I tried to "manually" switch over to 60Hz -- putting a +5V wire on leg 107. NOTHING happens!

I wanted to clarify if my +5V point is working, so I connected it to ground briefly and the unit resets, just like always. Conclusion: there's nothing wrong with my +5V source either.

[size=8]Yes, I KNOW you aren't supposed to connect +5V to ground, but I've done it with many systems and nothing bad has ever happened. The only thing that happens is that it resets the console. Of course, I've never actually CONNECTED +5V to ground, but just made them touch each other for a quarter of a second.[/size]

What in the world could be the cause of this? I mean -- it worked perfectly up until recently, so there can't be anything wrong with my mod, right?

This is a picture of my mod -- see? I've tapped pin 107 just as I'm supposed to. +5V has been tapped from just below it. Any other +5V source that I could try? Just for the heck of it?



The only possible answer I could think of is that the chip is broken somehow. But the system works great! Any ideas what the problem might be, or how to solve it?

Thanks in advance!

[NFG]

That's a weird one.  If everything you say is true, it should work just fine.

[FM-77]

Is it possible that "part of" the chip can stop working? Something that controls the video output or something of that nature. Or would that cause the entire machine to stop working?

[viletim!]

It's possible to kill a single input (or output) of a chip that otherwise works fine. One way you can check is using a multimeter to measure the resistance between ground and the 50/60Hz input, then compare the resistance with that of another digital input (disconnect it first). If they're wildly different then you've likely killed something.

[cd_breaker]

Hi all,

I am seeking some help with a problem i had while doing the us/jp mod to my Genesis II. I checked the info on gamesx and then this guide, which i followed:
http://www.mikeg2.freeserve.co.uk/masterful/md2lang.html

Now, I succesfully ran my jp Virtua Racing on my Genesis II, but the joypads' button mapping became weird, with the Start button no longer working where it should; now the C button acts both as C and Start at the same time, and the Start button doesn't work at all. Haven't checked X,Y and Z, but i'm guessing they are ok. The D-pad works ok, A and B too, i guess. (not that i can be 100% sure that A is A and B is B now, since i tested it with a Sonic 3 cart. Not the best choice, but the only one i had at the time besides Virtua Racing, which wouldn't start when i pressed the "C+Start" button >_<''')

So anyway, any ideas? I appreciate any help you could give me; posted this here since I didn't want to make an entire new topic of this. I hope you're ok with it.

Thanks for your time =)

[-Martin-]

Did you ever switch your switch while the console was on?
If the switches used were not Break Before Make (BBM) type switches then they may create a small short between 5V and GND while you switch, which after a while, can kill your chip if you do it often.

Or you could have simeply used on/off switches with no grounding, which would avoid this problem although your console may behave a bit odly as a result...

[atom]

Only thing I can imagine at all would be oxidation. And I doubt that. Sure, certain parts of a chip can malfunction, but the odds of the only thing breaking being your mod are next to impossible. What type of solder are you using? Acid or Rosin core? I used the wrong kind once and couldnt figure out what was wrong.

[FM-77]

Rosin core. Like I mentioned before -- the mod worked for a while (about a month) but then it just died. Been using the same solder for everything and I haven't had any problems with it.