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Dreamcast [DEV] : MOD Dreamcast REV0 (Va0) with GDEMU

therobotx5

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Hi, I recently bought a DC signature model from Japan. Would also like to do this mod. Are all Chinese Gdemu the same hardware?. Has anyone had any adverse affects from doing the mod? Much better than forking out £200 for a MODE. Cheers :)
I'm pretty sure they are all the same just with minor component variations such as the the sd card slot. My GDEMU is labeled "GDEMU v5.15b 2020-08-24" with the closed SD card slot I got on Ali express. I have attached an image of what I got. It is not yet tested since I am waiting for the 100 RAs. In terms of any adverse effects, what I have seen people do is add a 300 ohm 1 watt resistor to the 12 volt line and ground or remove the 12 volt regulator entirely. This is because there are no longer any components using the 12 volt line of the psu and all it it does is generate more heat. But this is not required it is just to reduce heat. I decided to remove the regulator entirely if you want to know what I did.PXL_20210324_195737767.jpg
 

deadlegion

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With my Japanese VA1 I pulled the original PSU and dropped in a pico that I got for around $25aud, already had an external 12v power brick (around 4A, but 2A does work) suitable for the pico so this is pretty much all I spent.
Clean the power connector pins but you shouldn't really use sandpaper to do that, you can use deoxit but I just used isopropyl alcohol.

If you've pulled your DC apart it's a good time to replace the controller board battery with a holder, don't use CR2032 batteries when you replace though make sure you use rechargeable 3V type like ML2032. You can replace the controller board fuse too (with a reset type poly switch) if you like but I haven't bothered atm, mine hasn't blown at any point from what I can tell anyway.

Another thing to do is general cleaning and maybe replace the thermal pads top and bottom of the mainboard.

The plus about pico psu replacement (besides the fact that there is less heat) is that the console will work anywhere in the world, it's only the external power brick that needs to suit mains power. I don't need to use step up converter for my DC now :)

My original Japanese PSU was still working fine, it is now boxed away with the original GD-ROM drive.
 

therobotx5

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I final got my 100 ohm RAs in and here are my results.PXL_20210323_190730974~2.jpgPXL_20210324_225538707~2.jpgPXL_20210323_190655469~2.jpgPXL_20210324_225359576~2.jpg
And it works. GDEMU installed in a VA0.
PXL_20210324_232353979.jpg

Now although it works I have not tested for a long period of time but based on the previous post and the explanation of the mod I would say this is a good solution.

And anyone wondering why the case is warped and dirty, this dreamcast survived a house fire.PXL_20210324_234332230.jpg
 

megavolt85

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Not that I would play Shenmue on DC anyway, any other significant titles affected by using 2A?
even if the console does not restart with the rest of the games, the power supply will still work at its limit and with prolonged use it may fail
 

deadlegion

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even if the console does not restart with the rest of the games, the power supply will still work at its limit and with prolonged use it may fail
Interesting, I only used a 2A for initial testing.
Is a Wii power brick ok to use (3.7A if I recall correctly?).
I'm using 4.1A with my DC at the moment but I had to change the plug to correct type (hence why I used 2A to begin with).
 

FamilyGuy

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Interesting, I only used a 2A for initial testing.
Is a Wii power brick ok to use (3.7A if I recall correctly?).
I'm using 4.1A with my DC at the moment but I had to change the plug to correct type (hence why I used 2A to begin with).
I've been using a GameCube brick for years without issues. I think it's 3.7A as well.

As long as you're over 35W, or something like that it should be fine.
 

truemaster

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now i see this mod. well i have my doubts. sure is gdemu safe since the g1 is on 3.3v now (or nearly there). but the whole g1of the va0 is made for 5v. so a long term testing is the way to tell. i will not be surprized if the console freeze or reboots and not because of the famous psu contact. i want to be wrong though but the va0 vs va1 in term of voltages is not just only resistores but the ic's as well
 

megavolt85

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i want to be wrong though but the va0 vs va1 in term of voltages is not just only resistores but the ic's as well

microcircuits have diodes that limit the voltage to the supply voltage, but there is also a maximum current strength when exceeding which the diodes burn out, resistors are just needed to limit the current

if you don't know, megadrive also has a 5 volt bus, and all old flash cartridges (and those sold on aliexpress) use an FPGA designed for 3.3 volts, but this does not prevent them from working for decades ;)

you can argue for a long time whether it is right or not, but it has been working for more than one decade and while some argue, others use

P.S. one friend of mine is engaged in the wholesale purchase of retro consoles in japan, he remade 30 consoles according to this scheme and sold them, before that he could not get rid of the VA0 batch because no one wants to play from the drive, and GDEMU cannot be installed
 

truemaster

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aside from what happen in megadrive you cant compare 2 different things. well if this va0 modification isn't gona backfire hell yeah why not?
 

truemaster

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what i meen is the megadrive cartridge is rated at 3.3v but work on 5v because is 5v tolerant. gdemu is 3.3v fpga too but not 5v tolerant. you alredy know this. this va0 modification is gdemu safe because is reduce the curent, else the gdemu would had toasted. my concern is the stability of the g1 at long term run because of this power reducing. again this stability concern of mine it isnt sure that will happen but a long term test is required to be sure
 
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