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

[L10N37]

@ L10N37
1) check the resistance of the resistor assemblies with a multimeter, perhaps you were sold 1000 ohms or 10000 ohms with incorrect marking
2) solder all contacts of the CN503 connector

As you can see from other users photos these are marked '1000', perhaps the last denotes the letter 'o' for ohms?
I've confirmed with a multimeter EXACTLY 100ohms They are 1% tolerance

https://au.element14.com/bourns/cay16-1000f4lf/resistor-array-4-100-ohm-1-smd/dp/2469496?ost=2469496&CMP=KNC-GAU-GEN-SMART-SHOPPING

I am tempted to do another board when i get time, I'm sitting on a stack of VA0 systems that all work but have a bad GD-Drive

 

[L10N37]

+ a new batch of GDEmu on the way, just in case.

Also I understand everyone will have a different opinion on the mod, I see it as a safe fix... with voltage being 'electrical pressure', the resistor is slowing that down and reducing current. We can make an LED work with a higher voltage using a resistor, and it dims it.. thats safe? So by comparison.

 

[megavolt85]

It's work for how many time before burn your GDEMU 3.3V on 5V logic level on your VA0 ?

the first converted copy has been working for almost a year

The GDEMU on VAO don't burn immediatly, it's work sometime with no modification, but it will dead after some time...

I read the same arguments from users of game consoles on cartridges while they made their assumptions everyone else played without any problems

The resistor array reducing current, but 5V is 5V.

what is the voltage at point "0"?

Is not good to compare this method with Evcerdrive MD2 (with cpld MAX2) with resistor array, because GDEMU has not the same architecture.

it is difficult to convince a person who does not understand how it works

 

[megavolt85]

the 'working' GDemu was always giving a red light

this behavior is typical for:
1) bad contact of SD card
2) poor contact of the CN503 connector
3) poor contact of the power supply

 

[Xrider]

this behavior is typical for:
1) bad contact of SD card
2) poor contact of the CN503 connector
3) poor contact of the power supply

OR cyclone 2 dead on GDEMU by 5V on bus.

I have already fixed that (sorry, french forum):
https://darius-saturn.com/forum/viewtopic.php?f=341&t=11978&p=274562

[/URL]

 

[megavolt85]

OR cyclone 2 dead on GDEMU by 5V on bus.

Have you ever read the description of the problem?
if the problem was in the dead cyclone 2, then the console would boot without problems with GDROM

 

[Xrider]

Avez-vous déjà lu la description du problème?
si le problème était dans le cyclone mort 2, alors la console démarrerait sans problème avec GDROM

Sorry I never tried installing GDROM 5V on the motherboard with mod 100 ohm resistors installed on it.
I just have a VA0 with BIOS + Flash memory swapped to 3.3V logic level

 

[L10N37]

I'm getting a blank screen for quite a few seconds, then it just sits at the white dreamcast logo for several minutes. No swirl animation. Then finally this

That's one GDEmu, the other one doesn't want to boot at all, nothing happens.
Hence, I think I got double unlucky, especially considering the fix for the red light was reflowing the IC legs and memory card legs etc.

 

[megavolt85]

I'm getting a blank screen for quite a few seconds, then it just sits at the white dreamcast logo for several minutes. No swirl animation. Then finally this

does the same thing happen with the installed GDROM?

 

[L10N37]

does the same thing happen with the installed GDROM?

Yes!

 

[L10N37]

New GD-Emu's not working either, I'll try another soon.

 

[L10N37]

New GD-Emu's not working either, I'll try another soon.

confirmed a faulty GD Emu in 2 different Dreamcasts (VA1 and modded VA0)

simply moved on for now, I'll probably remove that mod and clean the pads up and start from scratch on that board eventually but everything looks good under the scope. confirmed working fine on VA0 #2

 

[alukar3]

View attachment 9881View attachment 9882View attachment 9883View attachment 9884

is china Everdrive MD
if you do not understand why I posted them here, then I will explain
FPGA and flash in these cartridges are rated for 3.3V, and the bus for MegaDrive is 5V
Now look at how the levels are matched, the entire bus is connected through 100 Ohm resistors, which limit the current and prevent the FPGA from burning

GDROM is also connected through resistors, but from a nominal of 33 Ohm, it is enough to replace the resistor assemblies by 100 Ohm and you can not be afraid that GDEMU will burn out, while maintaining compatibility with all GDROM boards

That is, gdrom at 5v after replacing the resistors will also work?