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  • Joined: 15 Jan 2021
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Master System 2 Black Screen with artefacts
Post Posted: Fri Apr 14, 2023 11:03 am
Hello there!

I got a SMS2 not long ago but it does not work properly.
When I turn it on I get a black screen most of the times. Other times it is the black screen with some kind of artefacts (I'll attach pictures of everything).

A few things I've checked/done:
- Power supply is all fine. I've tested it with another SMS2 I have that works and it's all good.
- Voltage regulator is outputting 5V as expected.
- I've replaced most of the electrolytic capacitors on the board.

I've also been following the troubleshooting procedure explained here (repair.wiki SEGA_Master_System_II, I'm posting it like this because the forum doesn't let me post links) and everything is good. All the pins on every IC is getting the expected voltage.

Does someone have any experience with this issue?
Should I look into replacing the ceramic capacitors too? Any other suggestions?

Thank you!
sms2-black-screen.png (524.13 KB)
SMS2 Black Screen
sms2-black-screen.png
sms2-black-screen-artefacts-1.png (1.8 MB)
SMS2 Black Screen Artefacts 1
sms2-black-screen-artefacts-1.png
sms2-black-screen-artefacts-2.png (1.39 MB)
SMS2 Black Screen Artefacts 2
sms2-black-screen-artefacts-2.png

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  • Joined: 05 Sep 2013
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Post Posted: Fri Apr 14, 2023 12:58 pm
You're not getting any music either?

because if the issue was with VRAM chips, you would have corrupted graphics but the audio would be OK.

Did you check if the CPU is working? Check the RESET pin and you can test if the ADDR0 pin is around 2.5V, as that would mean it's basically 5V half of the time, which would indicate it's working...
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Post Posted: Fri Apr 14, 2023 1:50 pm
sverx wrote
You're not getting any music either?

because if the issue was with VRAM chips, you would have corrupted graphics but the audio would be OK.

Did you check if the CPU is working? Check the RESET pin and you can test if the ADDR0 pin is around 2.5V, as that would mean it's basically 5V half of the time, which would indicate it's working...


Thanks for the quick reply.

I'm not getting any music. When I turn on the console I just get static noise.

RESET on the CPU (IC1), PIN 26, reads 5V, so that's good.
ADDR0 on the CPU, PIN 30 according to the service manual, is reading 2.2V, I believe is good?

EDIT: While turn it on and off now, one of the times it showed this Alex Kidd screen, still no sound and it doesn't move from that screen 🤔 no idea what is going on.
Screenshot 2023-04-14 at 14.44.13.png (93.14 KB)
ADDR0 pin CPU
Screenshot 2023-04-14 at 14.44.13.png
Screenshot 2023-04-14 at 14.52.28.png (2.82 MB)
Alex Kidd displays
Screenshot 2023-04-14 at 14.52.28.png

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Post Posted: Fri Apr 14, 2023 2:13 pm
jvlobo wrote
While turn it on and off now, one of the times it showed this Alex Kidd screen, still no sound and it doesn't move from that screen 🤔 no idea what is going on.


If it gets this far, at least the CPU and the VDP aren't (completely?) broken! Check if some component is getting very hot. And I would start to suspect some component could indeed have aged badly...
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Post Posted: Fri Apr 14, 2023 2:29 pm
sverx wrote

If it gets this far, at least the CPU and the VDP aren't (completely?) broken! Check if some component is getting very hot. And I would start to suspect some component could indeed have aged badly...


The only componente I can see getting hot is the voltage regulator (~50C) but I guess that's normal for that component.

Ceramic capacitors C33 and C35 have some white parts on them 🤔 Those are the only ones I can see different to the others.
Could that mean they are bad? Maybe they overheated at some point.
caps1.png (2.12 MB)
caps1.png
caps2.png (2.15 MB)
caps2.png

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Post Posted: Fri Apr 14, 2023 3:32 pm
I doubt the ceramic capacitors are the problem.

It is a strange looking failure mode. My guess would be some fairly serious problem with the RF modulation / output. You're getting far enough to load tiles to VRAM but those colours look way off and you're getting some banding at the bottom. The sync looks like it might be good though - I guess the images are stable when you see them?

Did you say you had another working unit to compare it with? If so, I guess that means your receiver setup (TV & cables etc.) definitely works?

It's definitely the correct PAL/NTSC flavour for your receiver?
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Post Posted: Fri Apr 14, 2023 6:01 pm
willbritton wrote
I doubt the ceramic capacitors are the problem.

It is a strange looking failure mode. My guess would be some fairly serious problem with the RF modulation / output. You're getting far enough to load tiles to VRAM but those colours look way off and you're getting some banding at the bottom. The sync looks like it might be good though - I guess the images are stable when you see them?

Did you say you had another working unit to compare it with? If so, I guess that means your receiver setup (TV & cables etc.) definitely works?

It's definitely the correct PAL/NTSC flavour for your receiver?


I'm attaching pictures of both boards. They are not 100% the same board model. IC9 is different. Apart from that, the other ICs seem to be the same ones.
Also attaching a screenshot of the working one showing Sonic.
I'm using the same power and antenna cable for both.

Thank you!
SMS2-good.png (3.41 MB)
SMS2-good.png
SMS2-good image.png (2.64 MB)
SMS2-good image.png
SMS2-bad.png (3.14 MB)
SMS2-bad.png

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Master System 2 Black Screen with artefacts
Post Posted: Sat Apr 15, 2023 4:53 am
These are PAL consoles from the photos.

From the screenshot of Sonic from the GOOD console it looks like the AV cable to the TV could be flakey or the tuning of the TV is a little out. Both the Alex Kidd screenshot and Sonic screenshot have the same kind of interference.

No audio and the corrupted graphics pattern on screen could be an issue with the interface between the CPU and VDP. Check for broken traces between the CPU (IC1) and VDP (IC5) by testing the continuity for the following signals with the console turned off: /IORQ, /RD, /WR, A0, A6, A7, D0-D7.

If the built in game (Alex Kidd) always freezes at the same place it could be an issue with the address lines between the CPU and memory. Check for broken traces between the CPU, ROM (IC2) and RAM (IC3) by testing the continuity for A0-A15 between these chips.

Those 2 orange ceramic capacitors look damaged and should be replaced.

From the photos it looks like someone tried to “reflow” the solder joints on CXA1145P chip. If this isn’t your work, then someone before you tried and possibly gave up on trying to fix the console.

Good luck.
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Post Posted: Sat Apr 15, 2023 8:49 am
Long shot: what's going on with the leg of C54 - looks from the photo like there's no solder in the joint...
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Post Posted: Sat Apr 15, 2023 10:36 am
willbritton wrote
Long shot: what's going on with the leg of C54 - looks from the photo like there's no solder in the joint...


This is one of the caps I replaced. And yeah the right leg doesn't have a lot of solder on the pad, but I've checked for continuity and it's properly connected. I'll add more solder just in case 👍🏽

asynchronous wrote
These are PAL consoles from the photos.

From the screenshot of Sonic from the GOOD console it looks like the AV cable to the TV could be flakey or the tuning of the TV is a little out. Both the Alex Kidd screenshot and Sonic screenshot have the same kind of interference.

No audio and the corrupted graphics pattern on screen could be an issue with the interface between the CPU and VDP. Check for broken traces between the CPU (IC1) and VDP (IC5) by testing the continuity for the following signals with the console turned off: /IORQ, /RD, /WR, A0, A6, A7, D0-D7.

If the built in game (Alex Kidd) always freezes at the same place it could be an issue with the address lines between the CPU and memory. Check for broken traces between the CPU, ROM (IC2) and RAM (IC3) by testing the continuity for A0-A15 between these chips.

Those 2 orange ceramic capacitors look damaged and should be replaced.

From the photos it looks like someone tried to “reflow” the solder joints on CXA1145P chip. If this isn’t your work, then someone before you tried and possibly gave up on trying to fix the console.

Good luck.


Thank you for the tips, I'll check for continuity between all those points you recommended and I'll report back :)

EDIT: I've checked continuity between all those pins and everything is fine. I'll order some replacement ceramic capacitors and see if that makes a difference.

Regarding the CXA1145P chip (IC9). It has a couple of solder blobs because I had two wires connected before to get the RGB signal.
Now I'm using an RF-to-HDMI device that is connected to a capture device so I'm able to get video and audio in my computer.
Probably the AV cable is not the best one... I'll need to get a better one.

Again, thanks a lot to everyone :)
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