I modified my new Twin Fami to accept a model 1 Genesis PSU and it looks like I've paid the price for it. While playing an FDS game for nearly an hour, the screen started flickering and the disk drive head started moving without being prompted (!). I opened up the system after shutting it off and found that the heat sink for the 2SB941 power transistor got incredibly hot, so it turned out the system was overheating.
Now while the system still works fine (and even loads disks just fine), the disk drive head continues to move on its own (just like it was reading a disk) and nothing short of disconnecting the drive has fixed it. Even having the system in cartridge mode doesn't do anything. Anyone have any clue?
Hmm, how did you modify it? Could the MD1 PSU cause this?
I am actually running my twin on a 9V 1A power supply I found in a drawer and it is working fine so far...
I would suggest to replace the power board and see if it helps.
I assume the problem is there, because the rest of the console should only be getting 5V, right?
The voltage regulator seems a likely candidate to break from overheating. That could result in all kinds of problems.
2A03, check the switch "start of the track".
Quote from: fredJ on February 13, 2014, 11:44:50 pm
Hmm, how did you modify it? Could the MD1 PSU cause this?
I just soldered in a power jack that could accommodate the Genesis PSU, then cut the traces going to the solder pads for the jack and rewired them appropriately. I should also add that my Twin Fami also has an NESRGB board installed which increases the power draw on the Twin Fami.
After some troubleshooting on NESdev, I'm seriously thinking the FD7201 controller is at fault. All of the switches on the drive are good, so I think part of the FD7201 got fried and is causing this particular issue.
What is the temperature in your room?
Quote from: 80sFREAK on February 14, 2014, 04:48:09 pm
What is the temperature in your room?
Err it's usually between 65-70 degrees F, I don't see what that has to do with anything.
I noticed, that some units under 15 degrees C have failure of "start of the track" switch. It wouldn't short cut contacts. It looks like it's flipping but it's not. Push it little bit with tooth pick as see the result.
1) you plug the disk
2) bios powered up motor
3) bios waiting for "start of the track"
4) after this signal bios will read surface and stop motor
I did a thorough exam of the drive switches last night and they all checked out fine. I'm convinced at this point it's not a mechanical issue, there's most definitely something with the drive electronics, especially considering it only started doing this after the system overheated.