AES3-4 repair with low voltage.
- Thread starter kuro68k
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I traced out both the palette RAM chips and all connections look good, no shorts or breaks. So the chips themselves are suspect. I'll have to order some more. At least they are socketed now.
Edit: It looks like it is working!
It needs the composite fix thing to get rid of the checkerboard pattern. Graphics look fine, despite the palette RAM failure. Maybe it's some parts of the RAM that the game isn't using. I gave it a quick play, it seems okay, didn't check the sound yet.
It's weird that the diag ROM doesn't run, but maybe it's these used EPROMs I have. Waiting for a new bulb for the eraser.
I've been looking for an excuse to get a Retro Chip Tester Pro, but it doesn't support the CXK5864BSP anyway, or at least the website doesn't mention it.
I the mean time I need to tidy that inductor up. It needs fixing down somehow. Could use hot melt, or should I go the whole hog and use silastic?
Edit: It looks like it is working!
It needs the composite fix thing to get rid of the checkerboard pattern. Graphics look fine, despite the palette RAM failure. Maybe it's some parts of the RAM that the game isn't using. I gave it a quick play, it seems okay, didn't check the sound yet.
It's weird that the diag ROM doesn't run, but maybe it's these used EPROMs I have. Waiting for a new bulb for the eraser.
I've been looking for an excuse to get a Retro Chip Tester Pro, but it doesn't support the CXK5864BSP anyway, or at least the website doesn't mention it.
I the mean time I need to tidy that inductor up. It needs fixing down somehow. Could use hot melt, or should I go the whole hog and use silastic?
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I'm a bit embarrassed to post a photo, it's just hanging off the resistor leads I put in the holes, in mid-air. I'll rework it so that it is at least sitting on the PCB.
I need to have a look inside my SCART cable too. It's wired for mono audio, wondering if I should mod it for stereo as I don't need composite. Could take the audio off the headphone socket, or make a little PCB for it internally. I think I will want to do the RGB bypass as well, the output looks soft and dim via my cheap upscaler and I expect it won't be all that much better on my RGB monitor.
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- Dec 7, 2000
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I tried to rewire my scart cable to use the composite wire as left audio and it didn't work at all for some reason. I may need to get a custom scart cable made if I want a stereo one. For now I'm fine with sticking with the headphone out.
use the headphone jack, its what god made it for: stereo sound
no need to hack up an AES
Yeah... Just looking at the logistics of it. The SCART plug cable grommet isn't large enough for another cable to come out, but SCART plugs are not hard to come by so I'm not too worried about making a hole in it. It's more a question of how to do it in a way that doesn't stress or damage the audio cable. The DIN connector is moulded on mine so no way to modify that.
Okay, I fixed the palette RAM issue. First I got the diag BIOS to work by flashing it another dozen times. Sometimes a single flash verifies okay but doesn't work in-system on these older EPROMs.
It showed a lower palette RAM failure, but it was just a damaged pad I hadn't noticed. I probably did it when removing the ICs. After that, every test passed!
I hooked up some headphones and found that I am only getting sound on the left side. Have not checked the mono sound from the AV port yet. It's probably a bad op-amp or something, but I'll leave that for another day.
It showed a lower palette RAM failure, but it was just a damaged pad I hadn't noticed. I probably did it when removing the ICs. After that, every test passed!
I hooked up some headphones and found that I am only getting sound on the left side. Have not checked the mono sound from the AV port yet. It's probably a bad op-amp or something, but I'll leave that for another day.
I fixed the audio, it was just a bad solder joint. The problem now is that the inductor I found is too big and won't allow me to close the case. I'll have to find a smaller one somehow.
I've got a really bad checkerboard problem on the video, but the suggested cause is composite video on the c-sync pin, but they are not eclectically connected. I checked with my 'scope, it's got a clean sync signal on the c-sync pin.
Edit: It's the SCART cable, it's wired for composite, csync is not used at all. It's also got some resistors and 200µF caps on the RGB lines. Since the csync line isn't there at all I can't fix it. I also wonder if those resistors are causing the dim video. The caps are not needed, I upgraded the board to 480µF ones. Shame I can't fix, especially since those 262° DIN plugs are not easy to come by. I think I have a couple but they were for another project.
I've got a really bad checkerboard problem on the video, but the suggested cause is composite video on the c-sync pin, but they are not eclectically connected. I checked with my 'scope, it's got a clean sync signal on the c-sync pin.
Edit: It's the SCART cable, it's wired for composite, csync is not used at all. It's also got some resistors and 200µF caps on the RGB lines. Since the csync line isn't there at all I can't fix it. I also wonder if those resistors are causing the dim video. The caps are not needed, I upgraded the board to 480µF ones. Shame I can't fix, especially since those 262° DIN plugs are not easy to come by. I think I have a couple but they were for another project.
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- Joined
- Dec 7, 2000
- Posts
- 12,022
Do an RGB bypass mod.
www.retrorgb.com
Neo Geo AES "Basic" RGB Bypass
This page will show you a "basic" bypass for the Neo Geo AES console that eliminates the Sony CXA amp and sends video (at the proper voltage) directly from the NG's digital-to-analog-converter, to the multi-out. This was tested on the worst revision Neo-Geo, the 3-6, however it should work on other
www.retrorgb.com
I thought about the bypass mod, but I'm not sure if it is necessary or the best option. While I wait for parts for the new cable to arrive, I will experiment with this one. I'll remove the resistors and caps, see what difference that makes to brightness levels.
If I do modify the Neo Geo board, I'll probably do a source side mod and replace the 6.8k resistors with 3.4k. That seems safer - the Sony CXA amp can be replaced, but the DAC is part of one of the custom chips and thus much harder to source. I'm not sure I want the super crisp look anyway, why not just use an emulator if that's the goal?
I was wrong about the DIN plugs, they are 270° versions, so easy to get hold of.
If I do modify the Neo Geo board, I'll probably do a source side mod and replace the 6.8k resistors with 3.4k. That seems safer - the Sony CXA amp can be replaced, but the DAC is part of one of the custom chips and thus much harder to source. I'm not sure I want the super crisp look anyway, why not just use an emulator if that's the goal?
I was wrong about the DIN plugs, they are 270° versions, so easy to get hold of.
- Joined
- Dec 7, 2000
- Posts
- 12,022
Usually the 3-4 needs a bypass, and it's not that big of a deal to do it.
If you have jail bars like the images on this page, you might be able to get away with simply cutting some traces, as described here:
If you have jail bars like the images on this page, you might be able to get away with simply cutting some traces, as described here:
A simple jailbar fix for the Neo Geo AES
The Neo Geo AES. Back in the 90’s, everyone saw the Neo Geo machines in the arcades (known as the MVS, for Multi-Video-System; yes, even the ones that only h...
nicole.express
I don't think there are jailbars, but I might not be seeing them due to the checkerboard pattern. Once I have sorted that out I'll see if I think it needs a bypass mod. I like the idea of adjusting the signal before the amp though, it's safer.
Anyway I ordered the parts to build the cable and replace the inductor with a smaller one. Also the cap kit came with a 2200µF cap that is too tall, so I ordered a better one of those, and the caps for the AES3-4 audio fix. And finally the bits for the Saturn/Playstation to Neo Geo adapter I'm building. I should order the boards too.
Anyway I ordered the parts to build the cable and replace the inductor with a smaller one. Also the cap kit came with a 2200µF cap that is too tall, so I ordered a better one of those, and the caps for the AES3-4 audio fix. And finally the bits for the Saturn/Playstation to Neo Geo adapter I'm building. I should order the boards too.
A properly wired RGB SCART cable fixed the checkerboard. I haven't wired in the audio yet.
I am considering using a MAX1682 to generate 10V for pin 16, the 4:3 select signal. It's mostly a question of if I can jam it into the SCART connector along with everything else. Maybe if I trim some unused wires.
Edit: One other thing I forgot. I made a 9V power cable that uses USB PD, i.e. it has a USB-C plug on one end. You can get a "USB PD trigger" board from AliExpress that is basically just a USB-C plug that asks for 9V. These days I tend to convert most stuff to USB-C if I can, especially if the original was a 100V only model.
I am considering using a MAX1682 to generate 10V for pin 16, the 4:3 select signal. It's mostly a question of if I can jam it into the SCART connector along with everything else. Maybe if I trim some unused wires.
Edit: One other thing I forgot. I made a 9V power cable that uses USB PD, i.e. it has a USB-C plug on one end. You can get a "USB PD trigger" board from AliExpress that is basically just a USB-C plug that asks for 9V. These days I tend to convert most stuff to USB-C if I can, especially if the original was a 100V only model.
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