AES Red Screen -Now Blue!-

[Neo Alec]

I bought a couple of junk AES systems from Japan. This one boots to a red screen.

Here is what the 43256 chips looked like:


The first few pins at the top of the bottom chip (pins 25 & 26?) look highly suspect, and don't seem to be okay.

I tried reflowing the pins with flux and solder. Here is what they look like now:


It's still getting a red screen. Where are these pins supposed to run? Is there a schematic somewhere still online?

 

[Neo Alec]

I found the schematics here. I really appreciate that they were uploaded:
https://wiki.neogeodev.org/index.php?title=Schematics

I'm going to try to patch this. I don't know if I'm up to the task. I will update if I get stuck.

 

[Neo Alec]

I don't seem to be getting anywhere with this. Does anyone happen to know if this wire is even in the right place?



The schematics aren't that hard to read, but I'm questioning that both of these RAM's seem to have several pins going to the same place. This seems to be the one pin that wasn't connected to anything, but my multimeter seems to be giving me many false positives. I'm getting blips on several pins where it seems I should not be. I thought the multimeter was a suitable tool for this job. Do I need a logic probe?

I had a heck of a time getting my lead-free solder to stick to these old components. Do I need to use lead solder?

Any advice is appreciated!

 

[Neo Alec]

Learned a lot in the past few weeks. I found the AES Work RAM Pinout on Jamma Nation X. That helped A LOT! Thank you for this! I wish someone had pointed it out to me sooner.



There were four bad traces I had to patch. I managed to fix the red screen, and now it's blue! However, now it won't load games (I have two test games now). Having a cart in the slot makes a difference -- the self-test shows the fonts, etc, like the MVS self-test, rather than just stripes and garbage, but still loads to a blue screen. I'm afraid I have a Z80 issue now.

I have the chips to burn the Neo Diagnostic Bios coming this week. If I can manage to get my Willem EPROM programmer to work, I will put the Diagnostic Bios on here. I also have a test cart to load the M1 rom to.

Any additional advice appreciated.

 

[Xian Xi]

Clean the slot. If it's still blue it means it passes the hardware test but doesn't detect a cart.

 

[Neo Alec]

Yeah, I know. I cleaned with a tooth brush and rubbing alcohol, but it didn't help. Inserting different amounts and wiggling does nothing. I have a Daedalus now too, and it does the same thing as an AES game -- System is reading the cart for the self-test, but the game doesn't boot.

Do you think some Deoxit will help now? Slots appear good.

 

[Neo Alec]

Got the Diagnostics Bios in there. It says:

WRAM DATA (0000)
Address: 10481C
Actual: 0007
Expected: 0000

The address changes randomly when I reset.

Xian, you had the same problem here:
http://www.neo-geo.com/forums/showt...nostics-ROMs&p=3419273&viewfull=1#post3419273

I can get to the sub menu by holding ABCD, but I can't move, and as soon as I release them it resets.

Xian, you said the A8 interconnect was broken in your case. What does that mean?

When I use the Unibios, I get a solid white screen.

 

[Asure]

A8 interconnect is a probably a through hole on the pcb which connects to either A8 on the ram chips and /or the A8 on the cpu.
Checked the schematics for you, and A8 should go to both rams pin 3 and cpu pin 36.
Note that these schematics are confusing, and the original post you linked to was not clear if it was 'A8' from a cpu point of view, or A9 (ram pin 25 to cpu pin 37)

Let us know what you have patched with wire so far. Keep in mind that the adress lines should go to both the rams, not just one ram.)

 

[Neo Alec]

Thanks. I already fixed the red screen on the original bios by patching cables from the lower work ram to the 68K. I'm surprised there is still more to fix. I will have to check everything again.

Can I tell from the error that it is the lower chip?

 

[Xian Xi]

Check the address lines between both of the WRAM, CPU and BIOS.

 

[Neo Alec]

I've re-checked all of the connections between the 68K and the C2 and D2 wram. I had already repaired everything that needed to be, so everything checks okay. I checked all the connections between the 68K and the bios, which would mean the bios is connected to the wram too. So I don't know where to go next.

 

[Neo Alec]

edit: wrong thread

 

[Xian Xi]

Did you check the connection between lower and upper ram?

 

[Neo Alec]

What actually needs to be connected between the two? I was under the impression that if they're both going to the same place and they are both connected to that then it's enough. How can I tell what is directly connected?

 

[Asure]

Well, adress and data bus. i.e. A1 should come from the cpu and go to all the parts on the bus.
If you look at the schematics you posted earlier at https://wiki.neogeodev.org/index.php?title=Schematics
In this example A1 cpu pin #29 should connect with BOTH pin #10 on ram 3C and pin 10 on ram 3D. (and so on, up to CPU A15(pin #43) to RAM A15 (pin #1))

(Note that CPU A17, 18,19,20,21 should go to the NEO-C1 at 6E.)

Things will go wrong if you go by pin names! In this case there is no pin label A0 on the CPU, but the ram labels start at A0.. (CPU A1 goes to A0 on the rams..)
Make a table in excel or word, and copy it into this topic, verify everything.. There must be some severed connections still. (a data or adress line not going to both rams for example.)