I have a Dreamcast with an ODE (sometimes I insert a GDEMU, another times a USB-GDROM).
I wanted to make it cooler, and I don't want to remove the 12V rail, because I need it depending on the TV and cable that I'm using.
I decided to do the PSU resistor mod (adding three 1kOhm resistors in parallel between the 12V rail and GND) and upgrading the fan.
The fan, like many before me, I asked myself "why not use a 12V one to help consume power from the 12V rail"?
I could only find one DIY with a 12V fan:
http://randomprojectman.blogspot.com/20 ... tem-i.html
It's a cool mod, but the fan didn't have a signal wire, and I didn't want to go that way.
I also wanted to use 3D printed supports for the new fan, so I decided to use some made for a 5V Noctua fan:
https://web.archive.org/web/20200923143 ... unt_v6.zip
I bought a Sunon MF40101V2-1000U-G99, 40x40x10, 12V, with three wires. It's about the same size of the Noctua, but probably more noisy. The Sunon makes a little bit less noise than the original fan, but it's quite noisy.
The Dreamcast that I modded is an early PAL VA1, with the metal fan and a slighter bigger metal cooler/shield, like this one:
https://www.dreamcast-talk.com/forum/vi ... 42#p145842
To make everything fit nicely inside the Dreamcast, I heated an x-acto knife in the stove and cut some corners of the Sunon fan (do not cut the circular wall around the fan, I just removed the corners with the screw holes; the Sunon fan now sits on top of the metal cooler/shield).
It is possible that the original metal fan in this early VA1 Dreamcast helped to dissipate the heat from the metal cooler/shield inside, so in it's place I'm going to attach some metal fins with thermal paste to the metal cooler/shield.
I soldered the Sunon fan directly to the 12V rail and GND on the PSU, with a button in the middle (the button is on the positive wire, because if it is on the negative wire and if it is OFF while the Dreamcast is ON then the signal wire will get the same voltage that is on the 12V rail of the PSU), and I also soldered the three 1kOhm resistors with a button.
According to my measurements with a multimeter, I get 232V 50Hz from the wall and:
- with nothing connected to the 12V rail: 14.29V;
- with the Sunon fan connected to the 12V rail: 13.35V;
- with the three parallel 1kOhm resistors connected to the 12V rail: 13.35V;
- with the Sunon fan and the three parallel 1kOhm resistors connected to the 12V rail: 13.25V.
It's funny to see that the Sunon fan seems to consume the same as the three 1kOhm resistors (0.59W 40mA according to the data sheet).
Do you think I'm driving the PSU too hard with both the Sunon fan and the three 1kOhm resistors connected at the same time? Should I only have one of them connected and never both?
Now, about the fan signal wire, I still haven't connected it yet, because I'm afraid that the Sunon fan signal breaks something on the Dreamcast motherboard.
I have four possibilities:
- Keep the original fan also connected (not what I want);
- Do the same that is here: http://randomprojectman.blogspot.com/20 ... tem-i.html (not the ideal solution);
- Cut trace and bridge R627 as in here: https://www.dreamcast-talk.com/forum/vi ... hp?t=14259;
- Connect the Sunon signal wire to the original signal wire.
I could cut the trace and bridge R627, but cutting the trace is kind of a visually non-reversal mod (I could reconnect the trace at a later date if I wanted, but visually it would be not intact) and I don't want to do such an extreme mod to the motherboard. Anyway, if I decided to cut the trace and bridge R627, is it completely safe to the Dreamcast motherboard? The original poster writes "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" and I'm not enough knowledgeable to understand this.
About the possibility of connecting the Sunon signal wire to the original wire, I've made some measurements with a multimeter:
- Original fan signal wire measures 2.589 V DC, 1.735 V AC and 228 Hz;
- Sunon fan signal wire measures 0.12 mV DC, 0.022 V AC and between 1 and 40 kHz.
Is it safe to connect the Sunon signal wire to the original signal wire?
Thank you for your help. Hope my experience also helps others. If you need me to do more experiments let me know. I wanted to measure temperatures, but I don't have equipment to do it
