Dreamcast won't pass logo and video shuts down

[Kaleth1111]

Everytime I turn it on I can hear it's working and disk spinning but it shows the logo screen and for about one second the time and date set up screen is visible but almost immediately the video stops and I get the no signal screen at my tv, also disc stop spinning.

I tried also without a disk and also with the door open and does the same.

At times it only shows the orange light but is like nothing happens.

Any ideas??

[Ian Micheal]

what cable are you using?
might be power problem clean the pins etc
if your fan dont work it will shut down like that

is the fan spinning if not sound like the problem

[ShadowGeist]

IC601 is a Fail-Safe device. Interference between the fan tachometer and this chip will cause the DC to shutdown approximately 10 seconds after initial boot to protect components from possible damage caused by overheating even if the fan is running.

It's possible to diagnose an issue by connecting points located at R627 without cutting trace and testing.

Taken from Nold's guide...

Nold's Alternate Dreamcast Pinouts & Workarounds

Faking the FANs PWM-Signal

Why use Arduinos or 555's... damn... just use some solder!

Some background: The DC uses IC601 (a multivibrator IC) as some kind of ADC (Analog-Digital-Converter), to convert the PWM-Signal from the fan (up to 2.5v), to 3.3v (= logical "true"). So when there's no fan, it'll put out 0v (= logical "false"). So all we need to do is pull-up the output signal of the IC & done! How nice Sega prepared this mod for us & gave us some free solder-pads.. (It might be safer to use a resistor here, but it should even work without the IC, anyway; also there is a capacitor, protecting a possibly connected fan.)

Controllers & RTC

Every pair of filters is for one controller. They are connected to pin 1 & 5 of the controller. DON'T remove these filters! (There are connections on both sides of them).
The RTC voltage is connected to pin 2 of the connector, using a 10Ohms 1W resistor. Don't use a 3.3v Battery here! (The Dreamcast uses rechargeable batteries).
Last we have the PWM-Signal coming from the FAN. It's required for the DC to boot, but we won't need it...

[budokaiboy]

Thank you so much! I did the controller refurb mod. Fan stopped working. Re-flowed the solder pads, still no fan. I have the gdemu, so not much heat inside anyway. I have a noctua on the way. If the fan header is dead, I will tie in somewhere on the board and run the noctua when I power the DC on. It's running though, thanks to your post!