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Hiya friends!

I recently received my first Pal Master System 2 and it unfortunately has the dreaded black screen no sound. This is the version with the RF module only. I was able to test all cables on a friend's console and it worked completely fine.

I have repaired other consoles before but have never played around with a SMS2.

Here are a few photos of the board. I noticed that the fb7 line filter had loads of gunk on it but in the process of cleaning it broke off. The middle pin on the cartridge slot also had corrosion, which I cleaned the best I could.

If anyone could help me walk through a diagnosis I would be extremely grateful. Thank you so much.

20221020_091542.jpg (2.36 MB)

20221020_091512.jpg (2.07 MB)

20221020_082357.jpg (2.16 MB)

20221020_091632.jpg (2.2 MB)

20221020_091651.jpg (2.78 MB)

First thing first - can your TV display PAL images from RF? Make sure it can.

The console will not work without FB7. The 53MHz system clock passes through FB7. The "gunk" you tried to remove was actually glue to hold it in place to prevent it slowly breaking from vibration when the console is moved etc. That needs to be fixed first before anything else.

You could probably get away with soldering in a jumper where FB7 was, but if you want to fix FB7, then get some similar gauge of (insulated) copper wire, thread it though the ferrite the same way as the old wire, solder it back in, then add a blob of hot melt glue to keep FB7 from moving.

sverx wrote

First thing first - can your TV display PAL images from RF? Make sure it can.

I have tested my friends master system 2 and works perfectly fine with RF same model number.

asynchronous wrote

The console will not work without FB7. The "gunk" you tried to remove was actually glue to hold it in place to prevent it slowly breaking from vibration when the console is moved etc. That needs to be fixed first before anything else.

Ahh.. well that's a shame, I assumed it wasn't supposed to be there as the master system I borrowed from my friend to test and compare didn't have glue holding it down.
Despite that not being there it still provided the same result with a black screen. Line filter has been since fixed, where would we go from here?

Thank you both of you for the response and input! I appreciate it.

There's a service manual for SMS2 located at https://www.smspower.org/Development/SegaMasterSystemIIServiceManual

Maraakate wrote

There's a service manual for SMS2

Thanks for sending this through, I've just had a test of all the ICs and they are all coming back with 5v.

I'm not entire surely I understand how to test a video signal as it explains. The only thing I can think to do is go on a whim and replace all the caps.

My TV will pick up the RF Signal it's just completely black without any sound.

Apologies, I'm still learning about all this stuff, it's been a journey that's for sure.

NatoPotato wrote

My TV will pick up the RF Signal it's just completely black without any sound.

This looks like the VDP is creating a completely black image (so probably working) but no code is getting executed - it might be the CPU broken/halted or the BIOS not working properly (the CPU might be executing just NOPs...).

You could check the address 0 pin on the CPU, as it should be constantly changing if the CPU is doing something...

if it's not doing anything, I'd check the reset pin

Check the reset circuit. See what pin 46 of ic2 is doing. It should go from 0v to roughly 5v shortly after power on. Might be difficult to see with a multimeter, a scope would be better. A test you could do is power the console up and short the legs of c18 together with a screw driver for a second or so, then remove the screw driver and see if that wakes it up. If c18 has dried out it wont hold the system in reset long enough.. if its shorted instead then it will hold the system in reset for ever. If your changing caps do that one first and check if that changes things before doing them all.

sverx wrote

This looks like the VDP is creating a completely black image (so probably working) but no code is getting executed - it might be the CPU broken/halted or the BIOS not working properly (the CPU might be executing just NOPs...).

You could check the address 0 pin on the CPU, as it should be constantly changing if the CPU is doing something...

if it's not doing anything, I'd check the reset pin

It seems that it is 2.327v it seems to be sitting at if that's what you mean be checking?
Thank you so much for the response.

wasup wrote

Check the reset circuit. See what pin 46 of ic2 is doing. It should go from 0v to roughly 5v shortly after power on. Might be difficult to see with a multimeter, a scope would be better. A test you could do is power the console up and short the legs of c18 together with a screw driver for a second or so, then remove the screw driver and see if that wakes it up. If c18 has dried out it wont hold the system in reset long enough.. if its shorted instead then it will hold the system in reset for ever. If your changing caps do that one first and check if that changes things before doing them all.

Looks like it gets 5v a moment after switching the system on. I tried shorting the legs and I get some static type movement on the screen and when let go it just goes back to a black screen. C18 doesn't appear to be shorter.
I really appreciate the response. Thank you.

NatoPotato wrote

It seems that it is 2.327v it seems to be sitting at if that's what you mean be checking?

this is compatible with the fact that it should be rapidly changing between 0 and 5 volts, so it means it looks like it's running code - which further complicates this matter...

try checking data line 0, if it's pulling bytes from ROM/RAM this should be always changing too...

Author	Message
NatoPotato Joined: 20 Oct 2022 Posts: 4	Master System 2 Black Screen Posted: Thu Oct 20, 2022 1:47 am
NatoPotato Joined: 20 Oct 2022 Posts: 4	Hiya friends! I recently received my first Pal Master System 2 and it unfortunately has the dreaded black screen no sound. This is the version with the RF module only. I was able to test all cables on a friend's console and it worked completely fine. I have repaired other consoles before but have never played around with a SMS2. Here are a few photos of the board. I noticed that the fb7 line filter had loads of gunk on it but in the process of cleaning it broke off. The middle pin on the cartridge slot also had corrosion, which I cleaned the best I could. If anyone could help me walk through a diagnosis I would be extremely grateful. Thank you so much. 20221020_091542.jpg (2.36 MB) 20221020_091512.jpg (2.07 MB) 20221020_082357.jpg (2.16 MB) 20221020_091632.jpg (2.2 MB) 20221020_091651.jpg (2.78 MB)

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Thu Oct 20, 2022 7:31 am
	First thing first - can your TV display PAL images from RF? Make sure it can.

asynchronous Joined: 14 Aug 2000 Posts: 742 Location: Adelaide, Australia	Master System 2 Black Screen Posted: Thu Oct 20, 2022 10:51 am
	The console will not work without FB7. The 53MHz system clock passes through FB7. The "gunk" you tried to remove was actually glue to hold it in place to prevent it slowly breaking from vibration when the console is moved etc. That needs to be fixed first before anything else. You could probably get away with soldering in a jumper where FB7 was, but if you want to fix FB7, then get some similar gauge of (insulated) copper wire, thread it though the ferrite the same way as the old wire, solder it back in, then add a blob of hot melt glue to keep FB7 from moving.

NatoPotato Joined: 20 Oct 2022 Posts: 4	Posted: Thu Oct 20, 2022 11:31 pm
NatoPotato Joined: 20 Oct 2022 Posts: 4	sverx wrote First thing first - can your TV display PAL images from RF? Make sure it can. I have tested my friends master system 2 and works perfectly fine with RF same model number. asynchronous wrote The console will not work without FB7. The "gunk" you tried to remove was actually glue to hold it in place to prevent it slowly breaking from vibration when the console is moved etc. That needs to be fixed first before anything else. Ahh.. well that's a shame, I assumed it wasn't supposed to be there as the master system I borrowed from my friend to test and compare didn't have glue holding it down. Despite that not being there it still provided the same result with a black screen. Line filter has been since fixed, where would we go from here? Thank you both of you for the response and input! I appreciate it.

Maraakate Joined: 05 Jun 2010 Posts: 757 Location: Pennsylvania, USA	Posted: Fri Oct 21, 2022 2:39 am
	There's a service manual for SMS2 located at https://www.smspower.org/Development/SegaMasterSystemIIServiceManual

NatoPotato Joined: 20 Oct 2022 Posts: 4	Posted: Thu Oct 27, 2022 8:21 am
NatoPotato Joined: 20 Oct 2022 Posts: 4	Maraakate wrote There's a service manual for SMS2 Thanks for sending this through, I've just had a test of all the ICs and they are all coming back with 5v. I'm not entire surely I understand how to test a video signal as it explains. The only thing I can think to do is go on a whim and replace all the caps. My TV will pick up the RF Signal it's just completely black without any sound. Apologies, I'm still learning about all this stuff, it's been a journey that's for sure.

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Thu Oct 27, 2022 8:28 am
	NatoPotato wrote My TV will pick up the RF Signal it's just completely black without any sound. This looks like the VDP is creating a completely black image (so probably working) but no code is getting executed - it might be the CPU broken/halted or the BIOS not working properly (the CPU might be executing just NOPs...). You could check the address 0 pin on the CPU, as it should be constantly changing if the CPU is doing something... if it's not doing anything, I'd check the reset pin

wasup Joined: 05 Nov 2014 Posts: 435 Location: Auckland - NZ	Posted: Thu Oct 27, 2022 9:01 am
	Check the reset circuit. See what pin 46 of ic2 is doing. It should go from 0v to roughly 5v shortly after power on. Might be difficult to see with a multimeter, a scope would be better. A test you could do is power the console up and short the legs of c18 together with a screw driver for a second or so, then remove the screw driver and see if that wakes it up. If c18 has dried out it wont hold the system in reset long enough.. if its shorted instead then it will hold the system in reset for ever. If your changing caps do that one first and check if that changes things before doing them all.

NatoPotato Joined: 20 Oct 2022 Posts: 4	Posted: Thu Oct 27, 2022 10:36 am
NatoPotato Joined: 20 Oct 2022 Posts: 4	sverx wrote This looks like the VDP is creating a completely black image (so probably working) but no code is getting executed - it might be the CPU broken/halted or the BIOS not working properly (the CPU might be executing just NOPs...). You could check the address 0 pin on the CPU, as it should be constantly changing if the CPU is doing something... if it's not doing anything, I'd check the reset pin It seems that it is 2.327v it seems to be sitting at if that's what you mean be checking? Thank you so much for the response. wasup wrote Check the reset circuit. See what pin 46 of ic2 is doing. It should go from 0v to roughly 5v shortly after power on. Might be difficult to see with a multimeter, a scope would be better. A test you could do is power the console up and short the legs of c18 together with a screw driver for a second or so, then remove the screw driver and see if that wakes it up. If c18 has dried out it wont hold the system in reset long enough.. if its shorted instead then it will hold the system in reset for ever. If your changing caps do that one first and check if that changes things before doing them all. Looks like it gets 5v a moment after switching the system on. I tried shorting the legs and I get some static type movement on the screen and when let go it just goes back to a black screen. C18 doesn't appear to be shorter. I really appreciate the response. Thank you.

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Fri Oct 28, 2022 2:05 pm
	NatoPotato wrote It seems that it is 2.327v it seems to be sitting at if that's what you mean be checking? this is compatible with the fact that it should be rapidly changing between 0 and 5 volts, so it means it looks like it's running code - which further complicates this matter... try checking data line 0, if it's pulling bytes from ROM/RAM this should be always changing too...

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