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  • Joined: 17 Nov 2020
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SMS with distorted pixelated video output
Post Posted: Tue Nov 17, 2020 10:24 pm
So I bought this SMS used "not working" and it stays true to it's word. I cannot get this machine to stay working. I thought it might be a pin because one was lifted on the AV port so I soldered it and got a solid connection. That did not work. Also the RF does the same. It works sometimes but it is intermittent. I have yet to figure out what I have done to make a difference. The only thing I can possibly think of is maybe the CPU or the encoder, but those are impossible to find online for purchase. At first I thought bios, but I can't confirm this. I only have the built in game to test. I have a cartridge in the mail so I don't know if that will make a difference. If it is just bios, I should be able to disable it or at the very least replace the chip with Bock's.

For now, I am stumped. Can any of you think of anything that may be causing this? I reflowed every solder joint and checked every trace for continuity. Everything on the board itself seems fine, which tells me it would most likely be a chip. I just can't find any replacements.

I will put a listing in the market part of this site as well, but am hoping I can get some guidance.

I am posting pics of the board as well as 2 gifs.I know all of you know what the startup looks like but I posted mine to show that it does sometimes work. The other gif is the bootup when it malfunctions. It flashes red, then seems to boot into the system. I even get response from the controller. I can "play" a game of hang on, I just can't see it. When it works, everything works. I can play and hear sound perfect. When it malfunctions, I can only see what is on the screen in the clip. I hear sound but it is definitely not the sound from the game. It is 8-bit sound, just not what it is supposed to be.

Thanks in advance for any advice.
malfunctioning.gif (4.45 MB)
This is when it doesn't work
malfunctioning.gif
Functioning.gif (3.51 MB)
This is when it does work
Functioning.gif
Top.1.jpg (3.15 MB)
Top.1.jpg
Bottom.1.jpg (3.21 MB)
Bottom.1.jpg

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SMS with distorted pixelated video output
Post Posted: Wed Nov 18, 2020 2:26 am
When you say you have tried the AV port do you mean you have tried the Composite Video output and/or the RGB Video output and it gives the same results as the RF connection in the posted videos?

I can see some corrosion on that part of the board and also the RF Modulator. This would indicates that part of the board in particular was exposed to water.

The lid of the RF Modulator metal can has been removed. And it also looks like some tried replacing the electrolytic capacitors.
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Post Posted: Wed Nov 18, 2020 3:07 am
asynchronous wrote
When you say you have tried the AV port do you mean you have tried the Composite Video output and/or the RGB Video output and it gives the same results as the RF connection in the posted videos?

I can see some corrosion on that part of the board and also the RF Modulator. This would indicates that part of the board in particular was exposed to water.

The lid of the RF Modulator metal can has been removed. And it also looks like some tried replacing the electrolytic capacitors.


My apologies. I wrote this quick while at work.

By AV, I mean the port on the back of the unit. There are no mods and this is an NTSC unit so I don't have RGB, only composite. Is it directly related to RF output? Would that mean it might be the encoder? (IC9?)

The RF lid is off to show the components. I have the lid. I am the one that removed it to check for corrosion. I also have the 5v regulator heatsink removed for viewing purposes.

I am the one that replaced the capacitors on the board. I bought a kit online that came with the correct caps. I verified they were the same uf as well before installation. Do you mean tried as in to see if that would work, or tried and failed? Is something out of place?

I have also removed the pause and reset buttons temporarily because the rubber is torn. I have replacements coming as well as a new 5v regulator to try since it is one of the components I can find to replace that does not cost an arm and a leg.
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Post Posted: Wed Nov 18, 2020 9:11 am
It seems like there is a problem either with the VDP chip, the video RAM or the connections between them and the CPU. The messed up sound suggests it's not just the video RAM.
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VDP
Post Posted: Thu Nov 26, 2020 8:06 pm
Maxim wrote
It seems like there is a problem either with the VDP chip, the video RAM or the connections between them and the CPU. The messed up sound suggests it's not just the video RAM.


Looks like that may have been it. I was able to source some untested ICs and swapped them in to see a change.

First I started with the encoder. It worked for about 3 minutes of gameplay then started acting up again like in the video. Exactly the same.

After that I swapped out the RAM. No change at all.

Then I went for the VDP and swapped that out. It started right up and ran like a champ. I played a few different games for about 30-45 minutes of gameplay and it has not failed. I put everything back together and played some more.

All is well in the world of my SMS with hang on and snail maze.

On another note, I was gifted an SMS that was modded with s-video, component, and came with an FM sound board and a few games.

Best birthday ever!

3 for 3 as well because I was also able to repair the Atari I bought. Waiting on a video mod chips for that to come in because RF on those is worse than SMS 🤷🏻‍♂️.

Thanks for all the help!
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Spoke too soon
Post Posted: Fri Nov 27, 2020 7:11 pm
I guess I spoke too soon. It did it again. I'm really tired of this thing. I spent $40 on the console and I'm in about $20 in parts.

It's doing the crappy screen thing again. I have no idea why. I guess it's time to try the video ram chips.
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Post Posted: Sun Nov 29, 2020 5:38 pm
I replaced all the ram chips and even then bios. No luck. It plays for a bit each time and then goes back to acting up. I have my suspicions that it might be the oscillator crystal but I don't know where to find a replacement. I found a 10 pack from China but I'm in the US so that will take at least a month. Does anyone here know where I can get one in the states at a reasonable price? 10 from China is roughly $8 so I'd rather not spend more than that. I'll just wait if I need to.
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Digikey? Any help?
Post Posted: Mon Nov 30, 2020 8:07 am
I found a list for what looks like the same crystal on digikey but there are a handful of them that look the same. Is there any difference in functionality of these?

I searched 10.7386 (which is what is written on a label on the one attached to my console) on digikey and clicked crystals, oscillators, resonators and found these. Has anyone here has luck replacing the SMS crystal with any of these? Or does anyone have a recommendation on which one to use?

https://www.digikey.com/en/products/filter/crystals/171?s=N4IgTCBcDaIIwAYB0B2AzA...

Thanks in advance

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SMS with distorted pixelated video output
Post Posted: Tue Dec 01, 2020 12:39 pm
I'm not totally sold on the XTAL being at fault.

I pointed out in my above post that it looked like the rear edge of the board where the AV socket is had been exposed to moisture of water. I can see some residue near some of the components like R26 and C52 in the area between the AV socket and CXA1145. Have you tried cleaning the board with a pcb cleaning solution and giving it a really good wash with the solution and scrub with a soft toothbrush?

You mentioned that you reflowed all of the solder joints. Was this a reflow with fresh flux applied and new solder, or just heat up and melted? If it was the latter this will not unfortunately fix bad solder joints. :(

When it is playing up, have you tried measuring the voltage at each chip? Poking and prodding around with a non-conductor like a wooden chopstick can also be gold for finding intermittent faults.
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Post Posted: Tue Dec 01, 2020 10:49 pm
asynchronous wrote
I'm not totally sold on the XTAL being at fault.

I pointed out in my above post that it looked like the rear edge of the board where the AV socket is had been exposed to moisture of water. I can see some residue near some of the components like R26 and C52 in the area between the AV socket and CXA1145. Have you tried cleaning the board with a pcb cleaning solution and giving it a really good wash with the solution and scrub with a soft toothbrush?

You mentioned that you reflowed all of the solder joints. Was this a reflow with fresh flux applied and new solder, or just heat up and melted? If it was the latter this will not unfortunately fix bad solder joints. :(

When it is playing up, have you tried measuring the voltage at each chip? Poking and prodding around with a non-conductor like a wooden chopstick can also be gold for finding intermittent faults.


Fresh solder and flux. I did not get rid of all of the old solder but I did add some fresh solder with some flux and cleaned it off again.

I assume it has something to do with a clock speed but I changed the CPU. Granted it was untested, but it DID work, temporarily. This is why I thought maybe the XTAL. It's odd that every time I disconnect and reconnect a chip, or the XTAL and re-solder, it plays fine for a short time frame. It's almost like after the power is completely gone from the board it will work for a short time. I replaced the voltage regulator as well with no change.

I see the water damage area, but all of those pins in that area as well as the traces have continuity. I supposed I could detach the RF module and see. Maybe there is some pushback on the current? I don't know. The RF output does have 5v.

I did check output on the chips. From what I can tell there is 5v on all ICs as well as the cartridge connector.

I only have access to 91% IPA and used it to give the board a thorough cleaning on top and bottom.

It's really weird that I can play for almost an hour sometimes and other times it plays for less than a minute before going pixelated and distorted.
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SMS with distorted pixelated video output
Post Posted: Thu Dec 03, 2020 2:05 am
That's the nature of electrical faults where you have a bad solder joint, or damaged track, or internal damage on a chip. It's a PITA for everyone so don't feel bad. :)

Going by the photo I think you need more cleaning in the area I pointed out. I'd also use something like Servisol Electronic Circuit Board Cleaner spray which is purpose made to clean flux and other residue off PCBs.

The chopstick stick is a good trick to find bad joints and tracks. Literally, loosen the screws that hold the PCB to the case so you have some flex, poke around and see if anything triggers the problem or impacts it.
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Post Posted: Thu Dec 03, 2020 2:16 am
I kinda get what you mean but I have cleaned it since then. That picture is from after only replacing caps and it performed the same so I asked for help.

I removed all solder from the ICs and replaced it with fresh. The only thing I have done that to is the resistors and other components. Every cap and ic has a brand new solder joint and everything I could check for continuity on traces seemed acceptable. I'll try to remove some solder and add fresh to the resistors and go from there. I ordered a crystal from digikey. Maybe you're right. Maybe it won't have an impact but I won't give up on the board and I've tried everything else I can think of (besides new solder on the resistors 🤷🏻‍♂️) so I figured a dollar to add it to my cart of other things on digikey wasn't a bad investment.

I never have high hopes for stupid things like that so hopefully I'm not disappointed if it doesn't work.

Is there an alternative to the cleaner you advise? It seems that is not available in the states and I can't seem to find an equivalent to circuit board cleaner that doesn't redirect me to electronic connector cleaner.
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Post Posted: Fri Dec 04, 2020 12:29 am
asynchronous wrote

The chopstick stick is a good trick to find bad joints and tracks. Literally, loosen the screws that hold the PCB to the case so you have some flex, poke around and see if anything triggers the problem or impacts it.


You're saying put pressure on the board to see any changes in the output? I've already done that with a plastic stick. The only thing it did was change the solid color on the screen and still booted to the exact same distorted pixelated boot screen and only around the cartridge slot. But it does that even when it functions. It's sat for a few days now, I can go out pressure on the cart slot and hit power and it will flash a random color and then boot like normal but I don't know for how long it will play.
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SMS with distorted pixelated video output
Post Posted: Fri Dec 04, 2020 3:35 am
I'm not sure what PCB cleaners are available in the USA. Maybe a member from the USA can chime in on that?

I know that IPA doesn't always remove all dirt and flux residue from a PCB. This highlights the limitation of remote diagnosis and assistance. You can appreciate that telling someone in another part of the world to clean a PCB is one thing. What product, how much is used, how it's done, is something totally different.

Given the fixes tried and the capacitors and even VDP that have been replaced, I think you're nearing the end of remote assistance and probably need someone to have a second look at it.
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