Stumped again

[PyGuy]

Hi,
I have been working on a portable Dreamcast and realized I have been taking more downtime than actual work time. I finally decided to cut the crap and ask about alternatives to a PicoPSU to get a Dreamcast running on batteries. Bacteria was smart and found this workaround and I'm still scratching my head over technical difficulties with a PicoPSU-120. Can bacteria (or someone else) explain the alternative process? He did say something about using a "TI-card", but I'm not sure what that means. If I Google it, it comes up with the Texas Instruments site, leaving me even more confused. Can my friend Google be any more vague, even if Texas Instruments is actually what I'm looking for?

I have
A Dreamcast
A PSone Screen
Modding tools (Soldering Iron, Volt Meter, Screwdrivers, etc.)
A 12V Battery (4200 mAh) and 2 7.2v Batteries (both over 2aH) (No luck with either)
A PicoPSU-120

I need to know
What a "TI Card" is
How to hook it up to power a Dreamcast AND a PSone screen simultaneously.

Thanks in advance,
Andrew "PyGuy" Pyle

[sam_thornley]

What bacteria means by "TI card" is the Texas Instruments PTH08080 switching regulator. Or the PTH08000. There available as free samples from TI's website. I'm sure you've read people powering thier N64 portables with them. Seems to be a standard thing to use with N64 portables these days. You can set the PTH boards with resistors to give a desired voltage. For example two PTH08080 boards one set to 3.3v and the other set to 5v, to power a dreamcast board. A dreamcast's 12v line can be run off 7.5v insted, Works fine from what i've read. So for your batteries use 7.5v as that will be easier to power a PSone screen. Because if you use 12v as your system voltage, you will have to use a 7808 to power your psone screen. That will waste power/battery life because to 7808 is a linear regulator. Remember: never supply 12v to your psone screen. 12v will fry it. 7-8v is ideal for the PSone screen. No higher.

As for connecting up your screen there should be some wiring diagrams around here somewhere. Its pretty much self explanatory.

Hope this helps!

[PyGuy]

Thanks! This really helped a lot. Like I said, I have 7.2v batteries, will 7.2 power the Dreamcast? I can't find any 7.5v bbatteries.

[hailrazer]

Thanks! This really helped a lot. Like I said, I have 7.2v batteries, will 7.2 power the Dreamcast? I can't find any 7.5v bbatteries.

I know it will run off 7.4v Lithiums but it might not run off 7.2v , not sure.

[PyGuy]

Thanks. Since I have many 7.2v batteries laying around, I'll experiment with those. However, I'm confused by this whole thing about setting voltages with resistors. I checked google with no luck. Also, I'm clueless on what would go into the battery's + and - when I get to the 12v pin.

[PyGuy]

Never MIND! I actually finally got the dreamcast to run off batteries! My only question is...

How do I make a naked dreamcast think that it's closed. The disk isn't spinning...

[DiscoPanda]

How do I make a naked dreamcast think that it's closed. The disk isn't spinning...

When the lid is closed the gear on it presses a small momentary switch. Either find something to hold the momentary switch in the closed position or wire a non-momentary switch in parallel with it. A third option would be to jumper across the switch if you don't mind it always thinking that the door is closed, but you'd have to cut power to the unit to make it spin down the disc then.

[PyGuy]

I want to try jumpering. Will this work?

[DiscoPanda]

That looks about right, yeah.

[PyGuy]

Ok, so I tried soldering the two together (because they're so close together and small) but I'm still having no luck with the disk spinning. I also tried pushing the switch down with my thumb but I still get nothing.

[DiscoPanda]

Hmm... Is the ribbon cable seated properly? Not sure what else to suggest.

[marshallh]

That small pad is where a small 1206 SMD capacitor broke off. By soldering together those pads you have shorted something somewhere, probably 3.3v and GND. Not good.

You need to jumper the outer 4 pins. Which combination is required is up to you. I would use an ohmmeter and push the switch to find what is bridge when the switch is closed.