Sharp twin famicom crashing

[kannaloli]

Hi, I got a Sharp twin famicom and it crashes after maybe about 10 minutes in a game.

I thought it was the caps so did a full recap and it still has the issue. I went over all of the chips on the motherboard and touched up the solder joints and have also given the cartridge connector a good clean.

Someone elsewhere mentioned it could be the power regulator. I'm not sure what component that would be. There is a single B941 transistor on the power board so thought maybe thats what they meant. I got a replacement for this on ebay but now it will only turn on if I hold the power button down so I assume that this is the opposite type of transistor I need lol.Anyone know where to get the correct replacement?

I have tried touching the chips while the console is running but can't notice any of them getting particularly hot


Anyone know what the problem could be?

[P]

I assume they meant the voltage regulator, a 78'05 is normally used on 5 V systems like these including the original Famicom.

I guess the AC-adapter may also be old and worn out.

[kannaloli]

The only thing in there that looks like a voltage regulator is the B941 transistor. I'm not using the original power supply because I have 240v, I got one of these https://en.retrogamesupply.com/products/power-supply-for-nintendo-sharp-twin-famicom

[Stephen]

I would be curious if any of the components are suspiciously hot when the machine shuts itself off.

[P]

I see, I had no idea the Twin didn't use a 7805.

[emerson]

This sounds like a thermal shutdown situation at first glance. I suggest reflowing all solder points on all pcbs and not just the chips.

1. I assume you recapped the entire machine and not just the power supply board correct? And you double checked the cap polarities?

2. What are your voltage measurements at the power input of the CPU board both at first power up and after crashing? If you are comfortable leaving the console on for an extended period after a crash, measure the power supply pins of each chip before and after the crash.

3. Does this happen in both cartridge and FDS modes? With all games or a specific game? It could be possible a corrupt game could write to the wrong register resulting in a crash.

4. When the console is in the crashed state what do you see on the tv screen? If you hit the reset button after a crash what happens?

[kannaloli]

This sounds like a thermal shutdown situation at first glance. I suggest reflowing all solder points on all pcbs and not just the chips.

1. I assume you recapped the entire machine and not just the power supply board correct? And you double checked the cap polarities?

2. What are your voltage measurements at the power input of the CPU board both at first power up and after crashing? If you are comfortable leaving the console on for an extended period after a crash, measure the power supply pins of each chip before and after the crash.

3. Does this happen in both cartridge and FDS modes? With all games or a specific game? It could be possible a corrupt game could write to the wrong register resulting in a crash.

4. When the console is in the crashed state what do you see on the tv screen? If you hit the reset button after a crash what happens?

When it crashed the game screen was just stuck on whatever frame it crashed on, i dont think resetting did anything needed a power cycle. I have replaced the B941 transistor and it seems to be working okay now