Dreamcast just turns of periodically

[ZDragon]

I just got myself a PAL Dreamcast off eBay a while ago.
It was working pretty fine, but the system sometimes just turns itself off after some time (15-30 minutes) of playing!

I first thought it was because of overheating, because if i try to turn it on again afterwards, it immediately turns itself off while showing the Dreamcast logo already, so within the first ten seconds. However, even after waiting for an hour nothing changed there, and any heat would have dissapated by that time, certainly. Also, the error even happens in pause screens (so laser getting hot on poor discs isn't a problem).

Then I discovered that if i just remove the power cable for a short while and plug it back in after such a crash, the system will play again immediately (well, until the next crash at least). I have about another 15-30 minutes until I get the next crash.

I did have to short the F1 fuse a while ago because controllers wouldn't work, but it never was an issue and I doubt anything went wrong with that. I suppose the whole PSU would be fried then, not some weird periodic errors like this I'd say. Then again, I don't really know much about the internals of the Dreamcast so that's why I want to ask here if anybody knows this behaviour and can tell me what's wrong maybe...

[kendrick]

This sounds like one of the two classic Dreamcast failures. Either you have corroded power supply connectors inside the console, or your GD-ROM drive is failing in a way that causes the board to reset. Some of the issues are described in this thread:

http://nfggames.com/forum2/index.php?topic=312.0

I'm guessing it's the first one. You'll notice that there are separate screws holding down the power supply inside the Dreamcast, and that the whole board lifts up to expose six or seven vertical connectors, each about three centimeters long. These are the contacts you want to clean off thoroughly. Hope that gets you started.

[ZDragon]

I need to correct what I said before; just putting the power plug out and in again doesn't fix it in all cases, as I found out now.

The drive being the source of the error sounds unlikely to me because it also happens when there is absolutely no disc present. It could still be of course, but yea, unlikely.

So I will try what you suggested; thanks a lot for the really quick reply. However, I've never tinkered with a power supply before. Do I need to be careful because of possibly some voltage still being present in it after unplugging the power cable? Or to be more precise:  is there a risk of an electric shock, and if yes how can I prevent that?

[kendrick]

When the power cord is disconnected, the only power present is in the clock battery, and that's no hazard. You should be in no danger of electrocution as long as all the cords are pulled out.

Note that it's likely you'll have to lift out the drive mechanism in order to remove the power supply board and have enough room to clean the pins. Also, if you've never done it before you should be aware that the lid of the Dreamcast should be open when you disassemble or reassemble the case, because otherwise you'll break the sensor switch. Good luck.

[ZDragon]

Thank you for that info kendrick. So far when I've opened the Dreamcast I didn't have the lid open, but luckily nothing seems to have broken on the lid sensor yet.

Sadly your idea didn't solve my problem. I cleaned the connectors to the PSU thoroughly (although they were really clean already, no dust or oxidation visible).

Right now the Dreamcast doesn't even let me play at all anymore. It takes a maximum of 20 seconds (rather 10, like before) until the Dreamcast resets completely. No matter if there's a disc present or not, it also happens just inside the menu for example.

Do you have any other suggestions (except replacing the GD-ROM drive)?

[kendrick]

Does it actually shut down, or does it return to the menu after the failure happens? I've seen cases where the lid sensor switch goes bad, because it is a pretty fragile part. If that switch goes, then the Dreamcast can't reliably tell if the lid is up or not, which also leads to random resets. You'll need a multimeter or some other continuity tester to see if the switch stays closed or open reliably.

[ZDragon]

That can't really be. After all, why would it even reset then if it is in the menu to start with? If there is no disc present?

The games actually shut the console off (the LED is still on however, just no a/v signals are sent anymore). The disc stops turning when it happens. The fan doesn't even seem to turn to start with, as I just noticed O_o The cable seems to be quite a bit loose. Could this be the source of the problem?

I just investigated the fan and it seems like I hit it right on the spot. The fan plug's soldering connections to the controller board were broken and I simply resoldered them. Now all my problems seem to have disappeared! So I suppose the Dreamcast just shuts itself off when it notices that the fan is not spinning.

I still have a question, to prevent future damage to my console. What resistance does the F1 fuse have? The color coding on it seems not to fit the normal color coding on resistors (Orange-White-Silver-Silver  -   Green).

[l_oliveira]

I repaired a Dreamcast with the random reset failure a while ago. It was not the "classic" connector problem on the power supply,  neither a bad connection from the GD to the main board.
Instead it was our old known fault from other systems: "bad caps"
Sadly SEGA designed the PSU packed too tightly and the caps are placed too close to the secondary stage rectifiers heat sinks (which get quite hot) and that ruins the capacitors in the long run.

Replacing all of the big capacitors in the secondary fixed the said Dreamcast (a PAL unit with Panasonic/Matsushita power supply)