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  • Joined: 12 Apr 2022
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I think I ruined the cart slot *update* Fixed
Post Posted: Tue Apr 12, 2022 5:26 am
Last edited by aphexacid on Sun Jun 12, 2022 2:32 pm; edited 1 time in total
Hello everyone,

I recently bought a cheap “non working” US SMS, originally with the idea that it would just be for parts in case I need for my other units in the future. Indeed neither cart or card would work. it would just boot to the built in game. But before I put it away, I reflowed the pins on cart port and card port and to my surprise, the game cards now worked!

But instead of leaving good enough alone, I decided I was going to “adjust” the cart pins. Well I didn’t do a very good job looks like. They’re not very straight.
It’s at least recognizing a cart has been inserted. But I get a black error screen matter what game in put in, including an everdrive.

Is there anywhere I can get a replacement cart pin connector? I don’t know for sure if I messed it up, but I would mind desoldering it and replacing it.

Anything else I should look for as a fix? Caps?
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I think I ruined the cart slot
Post Posted: Tue Apr 12, 2022 11:07 am
Try cleaning it with paper before giving up on it.

Get some plain white paper, fold it a few times so it has some thickness, then insert it and remove it repeatedly in and out of the connector as if the paper was a PCB.

The paper is grippy enough to remove dirt and tarnish, but not abrasive to remove the protective coating.

You may also be able to see on the paper which pins of the connector are not making a physical connection with the cartridge.

Good luck.
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Post Posted: Tue Apr 12, 2022 3:49 pm
There are connector replacements, or at least, there were... I remember replacing a faulty one several years ago. I bought it on TOTOTEK. I'm sure you can find them somewhere else. But, as aphexacid said, try repairing it before replacing it entirely...
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Post Posted: Tue Apr 12, 2022 9:24 pm
Not sure where you're based, but the cart connector is a fairly standard 2.54mm / 0.1in pitch 50 pin edge connector so you should be able to find it readily.

I bought this one in the UK for a homebrew clone project and it accepts real SMS carts just fine:

https://uk.farnell.com/amp-te-connectivity/5530843-5/card-edge-conn-dual-side-50...

It's a pita to desolder a 50 pin connector if you don't have to, though, so as others say, better to see if you can salvage the original. There's really not much to go wrong in them unless you've exposed it to some tremendous heat. A fault's likely to be either with the solder joints or with internal oxidisation of the contacts. Failing that, there's a chance it's some other components and your reflowing of the cart connector was either a red herring or partially alleviated some intermittent fault.

Edit: you probably also want to check for lifted tracks around the connector. I'd imagine that could be an issue given the combination of age, normal stresses from plugging / unplugging cartridges, and your recent rework.
The fact that you're getting a "black error screen" as you say would also suggest to me that it's most likely you've got a fault on one or more of A0..13 or D0..7 because the BIOS is getting some response back from the cart but nothing it can make sense of. In fact, most likely one of D0..7 I'd say, followed by the low A lines.

If you took the case off a cartridge, plugged it into the slot and did some continuity checks between the main board and the cart board you might get somewhere.
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Post Posted: Wed Apr 13, 2022 6:14 pm
How do the pins look? I tried the paper buffing as suggested. There was definitely some black on the paper, but I can’t tell if any pins aren’t making contact honestly. I have to try it now to see if it did anything. If the pins look out off whack, should I try and bend them more or replace the connector?

I have to go over the board again, I’ve honestly never seen such dry looking solder. I’ve repair a few NES front loaders that were older and looked a million times better.

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Post Posted: Thu Apr 14, 2022 8:31 am
The alignment doesn't look too bad to my eye but it's hard to tell.

The wipers only need to make enough pressure to cut through the surface layer of oxidation to bond electrically with the cart connector edge which with clean surfaces is minimal pressure. If there is significant dirt or tougher oxidation in the way it won't be able to connect properly regardless of the alignment and the surfaces will need restoring.

It all comes down to resistance in the end. You can see conn 4 which is the expansion port next to the cart slot. In the SMS 1 that exposes the entire bus of the cart slot, so you have a perfect reference point to measure the cart connector's resistance. If I were you, I'd:

1. Clean the expansion port (conn. 4) pads so they are a good reference point
2. With your multimeter, probe the resistance between each pad on the expansion port and the corresponding wiper inside the cart slot. They should all read very close to 0.
3. If that all checks out, insert a "näked" (i.e. case removed) cartridge into the slot, either fully or partially, and do the same exercise but this time measuring the resistance between the expansion port pad and some point on the cartridge so you can be sure each wiper inside the connector is working properly.
4. I'd also check for short circuits at this point, although I think it's unlikely that's your problem. With the cartridge fully inserted (this is your current failure mode) and, again on the expansion port conn. 4, test each adjacent pair of pads with a continuity check. If you get continuity between any two adjacent pads it may be sign that something inside the connector is shorting when a cart is inserted. Check horizontally adjacent pins as well as "opposite" pins on both sides of the slot in case something is bridging between the two sides. Note that some pins are supposed to be connected together - IIRC I think it's just the three ground pins in the SMS (pins 19, 20 and 21)

If all those tests pass, you've basically eliminated the cartridge slot as being the problem. In that case, assuming you still see the failure with the cartridge but not with the built-in games, the problem is somewhere in the path between the cartridge slot and the CPU.

If you get either a high resistance or an unexpected short at any point, you need to investigate further. I should point out that since you say Sega cards don't work either, and since the cards and the cartridge share a large part of the system bus, there's a chance that there's actually a fault in the card slot which is affecting both at the same time.

Good luck!

Edit: you might also want to do the short circuit test with no cart inserted before you do anything else. I'm really reaching now, but do I see something shiny in the gap between pins 45 and 46, near the top of your photo?
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Post Posted: Thu Apr 14, 2022 4:49 pm
Thank you so much for all that awesome information. I will get to testing it. I really want to get this working
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Post Posted: Thu Jun 09, 2022 5:47 am
Good and bad news. I got the cartridge slot working after a reflow of these old and dry points. So A+ for that.

Bad news, is that I figured I’d give it a recap.
All went went well until I got to this bit, as seen in the picture. Now I get no sound, with RF at least. Haven’t tried the multiout yet.

Any suggestions?

Edit: thought I had a bite on the tiny bit of what was left, and then the whole trace broke off. Sigh.

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Post Posted: Thu Jun 09, 2022 7:48 am
What's on the other side?
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Post Posted: Thu Jun 09, 2022 5:06 pm
C51 cap

Not getting anything out of the multiout at all

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Post Posted: Thu Jun 09, 2022 6:00 pm
aphexacid wrote
Good and bad news. I got the cartridge slot working after a reflow of these old and dry points. So A+ for that.

Bad news, is that I figured I’d give it a recap.
All went went well until I got to this bit, as seen in the picture. Now I get no sound, with RF at least. Haven’t tried the multiout yet.

Any suggestions?

Edit: thought I had a bite on the tiny bit of what was left, and then the whole trace broke off. Sigh.


Looks like it's isolated on the top of the board, should be fine to bridge the break with a bit of kynar wire from the other end of the broken trace to the leg of the cap. Push the cap leg through the hole a bit more so it's easier to solder on to.

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Post Posted: Thu Jun 09, 2022 6:17 pm
Either that or use a new cap and bend the leg down and solder it straight onto the intact pad - that might help secure the component in place as well.
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Post Posted: Thu Jun 09, 2022 6:52 pm
willbritton wrote
Either that or use a new cap and bend the leg down and solder it straight onto the intact pad - that might help secure the component in place as well.


Good idea!
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Post Posted: Fri Jun 10, 2022 1:19 am
I tried a jumper wire from cap leg to where the trace goes, as picture above with the arrow.

Still no sound, but video from multiout works now.

Am I chasing the wrong thing for sound? Could it be something entirely different? Had to have been something I did because sound worked before.
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Post Posted: Fri Jun 10, 2022 7:30 am
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Am I chasing the wrong thing for sound?


Quite possibly.

The PAL schematics for the SMS1 are on this site https://www.smspower.org/uploads/Development/SegaMasterSystemServiceManual.pdf but since you said you have a US SMS I think the schematics must be slightly different as I can't immediately correlate them to your photo, although they feel closely related.

I'd start from pin 19 of the VDP which is the audio output, and trace continuity from there. As you can see from the PAL schematics this does go into a C51 but I'm inclined to suspect it's actually a different C51 from the one in your photo and it's just a coincidence. Not sure though!

Next you've got the audio out from IC9 which I'm not sure will be the same device in the US model, but if it is then you're tracing from pin 9 of that out to both CN1 (a composite connector) and also the RF mod.

How are you connecting your TV - are you trying both RF and multi out and no sound on either? If so, would suggest something between VDP and IC9 (on these schematics, so here I'd be looking at C51, R18 and C19 as persons of interest, like I said, suspect different component numbering on your model). Don't forget the tracks could be the problem too, especially since you're desoldering components.
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Post Posted: Fri Jun 10, 2022 7:36 am
P.S. did you check the volume on your TV? ;)
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Post Posted: Fri Jun 10, 2022 8:40 am
It’s got to be something with that C51. Everything was working perfectly after I got the original problem (cartridge slot) fixed. Video and audio perfect.
Then I got to recapping and that trace got lifted.

Sound went out, and then I fiddled with it a bit. And it came back. But it wasn’t a solid connection, and when I tried to make it better, it came off. Video went with it.

The jumper wire is kind of shoddy, so I’m going to put in a new-new cap and leave the leg long and solder strain to where it should go.

I’ll test out the suggestions as well.
Today I took some time to reflow the entire board. Every single bit is now nice and shiny. Didn’t help the cause though.

Also, volume on both tv’s I tried on maxed. RF video/ no audio. Multiout, scart /retrotink 5x - video no audio. Even tried HDRV component cables. No audio. The video looks damn fantastic though!
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Post Posted: Sat Jun 11, 2022 2:49 am
All fixed up gents.

@Willbritton I followed all of your suggestions best I could. I think since I have a NTSC board or the revision possibly, it’s lay out is a bit different.
All had continuity though.

In doing continuity tests, my eye notice a floating blob of solder. A new cap that I installed. And another pad ripped. *huge facepalm*.

The C37 cap, one leg pulled the trace almost completely off. Only if you physically push down on it would get continuity to the vdp chip.

So connected a jumper, fired up her up, and she lives!
So happy I was able to save her. But I have learned, if you’re doing a recap on one of these old birds, be very gentle. So many traces broke on me, more than anything before . And from what I’ve read, it’s not this particular unit. Even though it has been mistreated and basically trashed.

So In the end, I hope this serves as a help to someone with a Similar problem.

If you cart slot or card read are not working, but built in game works, start with reflowing both of them.
If doing a recap, be extremely gentle.

Thank you all for the help, lots of great people on this board.

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Post Posted: Sat Jun 11, 2022 8:44 am
Well done indeed for getting it working @aph, it's fantastic to be able to restore something like this and save it for who know many years to come!

Yeah true about the tracks, any part or component containing chemicals which degrade like PCBs or electrolytic caps are likely to fail over the fullness of time, although who knows perhaps those tracks were lifting like crazy even when the board was new - I'm sure PCB technology has moved on since the 80s! And at least it's a nice simple 2 layer board too...

Happy gaming!
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Post Posted: Mon Jun 13, 2022 1:00 pm
aphexacid wrote
All fixed up gents.

@Willbritton I followed all of your suggestions best I could. I think since I have a NTSC board or the revision possibly, it’s lay out is a bit different.
All had continuity though.

In doing continuity tests, my eye notice a floating blob of solder. A new cap that I installed. And another pad ripped. *huge facepalm*.

The C37 cap, one leg pulled the trace almost completely off. Only if you physically push down on it would get continuity to the vdp chip.

So connected a jumper, fired up her up, and she lives!
So happy I was able to save her. But I have learned, if you’re doing a recap on one of these old birds, be very gentle. So many traces broke on me, more than anything before . And from what I’ve read, it’s not this particular unit. Even though it has been mistreated and basically trashed.

So In the end, I hope this serves as a help to someone with a Similar problem.

If you cart slot or card read are not working, but built in game works, start with reflowing both of them.
If doing a recap, be extremely gentle.

Thank you all for the help, lots of great people on this board.


Great job, make sure you trim the excess length of the legs with a nail clipper or small wire cutters. Be mindful where that leg ends up flying. Sometimes can end up on your board then short something else out ;)
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Post Posted: Mon Jun 13, 2022 7:01 pm
Thank you!
I’ve got a few of those legs straight to the forehead!

Here’s a funny story;
I reached out to the man that sold me the unit. And to them I fixed it, and asked him how it came into his possession. He told me that his neighbors basement flooded about 10 years ago, and they threw out a bunch of things that were water logged. He went and picked through some things and put them for sale.

Someone else purchased this unit, but brought it back because only the built in game worked.

So I came across it and jumped on it. My all time favorite console. Got it new when I was a kid, I’ll never forget that day. I have a couple other units, including my original one.

I’ve fixed nes consoles a plenty, but honestly never had one peep of a problem from my SMS.
So happy I was able to revive it. The case was in bad shape, lots of broken pieces. Broken bosses, missing plastic bits. The metal shields took hours to remove the rust with a rotary tool. And it still doesn’t look very pretty.

I’ll get a picture up when I finally put it back together.
I wish I would have taken a picture of the board when I first got it. Absolutely disgusting.

Thank you all again for the help!
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