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  • Joined: 27 Jul 2019
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Sega Master System software error
Post Posted: Sat Jul 27, 2019 8:13 pm
I have an original Sega Master System (no built in game) and every cartridge I try gives the 'software error' message.

I have fully cleaned the cartridge slot and the games work in another console. I have reflowed the solder where the cartridge slot meets the board and every pin has good continuity.

I'm now at a loss as to what the problem could be. A faulty chip perhaps? But which one?

Unfortunately I have no card games to test.

Many thanks in advance!
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Post Posted: Sat Jul 27, 2019 9:24 pm
It's likely the cartridge slot, can you check continuity between a plugged in cart and the slot pins?
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Post Posted: Mon Jul 29, 2019 10:08 am
I’ve double tested continuity between the contacts on a known working cartridge and the underside of the cartridge connector and all is good with no shorts.

All this tells me that all is well with the cart slot.

Could the software error be generated in another way? Bad capacitors or a faulty chip?
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Post Posted: Mon Jul 29, 2019 1:11 pm
Software error means the BIOS is working, it has found the cartridge but either the region or checksum checks have failed. The latter is most likely, and suggests some problem between the IO controller and the cartridge slot.
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Post Posted: Mon Jul 29, 2019 2:51 pm
Thanks. Which chip is the IO controller? I can’t see any damaged traces but if I can pinpoint the location of a possible problem I’ll look closer. I’m curious if a card game would work and will try and get one.
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Post Posted: Mon Jul 29, 2019 5:26 pm
MadFox wrote
Thanks. Which chip is the IO controller? I can’t see any damaged traces but if I can pinpoint the location of a possible problem I’ll look closer. I’m curious if a card game would work and will try and get one.


well, that depends on the revision. for instance the IO chip on mine is front center right behind the controller ports and in between the VDP on the left and the MyCard port on the right. The chip is the SEGA 315-5216 but this may be different on other revisions.
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Post Posted: Mon Jul 29, 2019 6:59 pm
Great, many thanks!
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Post Posted: Thu Aug 08, 2019 1:50 pm
So I got hold of a working Sega Card (Hang On) and that gives the software error too. Definitely a problem other than the cartridge connector. I can see no damage near the I/O chip but will press on.
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Post Posted: Thu Aug 08, 2019 3:22 pm
a simple reflow never hurt in my opinion! Though you should examine the traces as well. A few years ago I received an SMS that wouldn't even turn on because of the thinnest hairline crack that spanned a good section of the back of the board. It was apparently deep enough to separate many of the traces. Was tedious but fixable though and got it working in the end.
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Post Posted: Thu Aug 08, 2019 9:55 pm
Last edited by wasup on Fri Aug 09, 2019 12:20 am; edited 2 times in total
Check that pin 43 (JyDis) on the cart connector is 0v and not 5v. If its 5v then you have a short, or dirt thats become resistive, between a neighbouring pin. Likely in the cart connector or on the expansion port (assuming its a sms1). Fix that and it will come right.
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Post Posted: Thu Aug 08, 2019 10:23 pm
maybe a short between two address or two data lines? even if I wonder how could BIOS work but you never know...
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Post Posted: Sat Aug 10, 2019 3:02 pm
wasup wrote
Check that pin 43 (JyDis) on the cart connector is 0v and not 5v. If its 5v then you have a short, or dirt thats become resistive, between a neighbouring pin. Likely in the cart connector or on the expansion port (assuming its a sms1). Fix that and it will come right.


Pin 43 shows 0v. I desoldered the entire cartridge connector and resoldered it today. Continuity is good between a game and the bottom of the board.

There are no broken traces anywhere so I’m at a loss. I’ll keep an eye out for a donor board on eBay.
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Post Posted: Sat Aug 10, 2019 4:12 pm
Did you check continuity on the address bus throughout the system? it really sounds like the address bus is broken somewhere.
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Post Posted: Mon Aug 12, 2019 7:34 pm
IllusionOfMana wrote
Did you check continuity on the address bus throughout the system? it really sounds like the address bus is broken somewhere.


Many thanks for your advice. I spent a lot of time today probing the address lines and found one without continuity. It was A14 (pin 7 on cartridge connector) which should have been joined to pin 3 on the Z80. I joined these with a bodge wire and carts now load fine.

The card slot still gives the same software error despite all address lines checking ok. I’m not sure if my bodge has disabled the card slot but I’ll keep checking things. At least I’m halfway to a working SMS1.
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Post Posted: Mon Aug 12, 2019 7:53 pm
that's so good to hear!
No doubt you can definitely get the card slot running too then!
Perhaps with the MyCard slot, testing the control and power bus next would be a good start.
Mainly testing to see that all 5v lines, all GND lines, and some of the control lines like RD, CE, and M0-7 are connected to their sources.
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Post Posted: Tue Aug 13, 2019 5:03 pm
IllusionOfMana wrote
that's so good to hear!
No doubt you can definitely get the card slot running too then!
Perhaps with the MyCard slot, testing the control and power bus next would be a good start.
Mainly testing to see that all 5v lines, all GND lines, and some of the control lines like RD, CE, and M0-7 are connected to their sources.


The card slot is still proving troublesome. Every pin has been cleaned and has continuity to the bottom of the board. Every solder point here has continuity to everywhere it should. The card I’m using is supposed to work but I can’t rule it out as not faulty so I’ve got a known working card on the way just to be sure.
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Post Posted: Fri Aug 16, 2019 11:32 am
I’ve received the new Sega Card (Ghost House) and it runs fine. So my Hang On Card is faulty. The original software error was all due to the broken address line described above.

I’ll have a go at fixing the card now. Many thanks for all the help.
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Post Posted: Fri Aug 16, 2019 5:35 pm
Glad you managed to get it sorted!
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