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**slightly cross-posted**

I plugged an NTSC NES PSU (acros!) into one of my SMS' the other day and that killed it. I tried replacing the voltage regulator and I accidentally installed it backwards so now I have to find service manuals or something so I can test each component to find out which one bit the dust.

It powers on but the screen is black and I remember I could feel one of the RAM chips getting hot so I'm sure it was probably one of those that got killed in the process.

Is there a service manual for the SMS itself? If not, I know omp and few other fellows on here probably know what points to probe so I could find out what indeed failed. The caps all look okay, none look popped and I don't see any obvious blown traces (there was no smoke), etc.

Installing 7805 backwards will give the chips some 7V or more, it is quite like most of the chips are fried. Only survivor would be the RGB encoder chip and even that is unlikely.
Without an o-scope you won't get far. Multimeter won't really show signs of life on various signals in the system.
But you should replace the RAMs and other chips that get hot. I am not sure how practical is it though... Some big parts only come from another SMS.

Would it fry the first chip in the series and cut the flow to the others so they coudl be potentialyl spared?

I think the RGB encoder might have survived because the screen will turn black. When it was installed backwards it showed some funny colours, etc on the screen.

I do have a complete spare board and all the ICs are good on it. I was originally trying to do a no-BIOS mod on that one and I cut the wrong traces and I just never finished it.

I just picked up an oscilloscope a few days ago. So, if you give me the proper points to probe we could figure this out. :)

Good place to start are various CLK signals. CPU, subcarrier, Master, VDP etc. If any clock is missing you'll have problems. You did get black screen so at least Master and VDP clock should work.
Then you can start looking at system data and address bus, when there is no activity on there you'll know the CPU is not functioning
VDP will start with faulty VRAM but CPU won't. Also the BIOS ROM might be dead too, but you should still see activity on address bus at that point for a while.

Is it as simple as locating the CLK pin on the IC and putting one probe on that and the other on GND? Never used o-scopes before so I will need some small hand-holding, heh.

Basically yes
Choose approporiate time scale and voltage
Center the line
Probe.

The longer the time scale the more you will see on the screen. There should be trigger option too, so toy around with it so it locks on to the waveform.

Okay. It will be about a week or so before I can pickup the o-scope to do some tests. In the meantime, have you ever attempted the no-BIOS mod. One could get lucky, but I doubt it.

My SMS2 now has improved BIOS bypass which uses both !CARTCE and !BIOSCE for the cartslot. If it didn't then my SMS stuff will not function as I take over the memory control register.

I'm going to try it on an SMS1. The 'parts' SMS1 I have was from a failed no-BIOS mod. I probably cut the wrong trace or something or other. That's why I wanted confirm if someone has done it with an SMS1. I'll just need to double check carefully as I do everything.

I did notice that that 315-5214 gets hot almost instantly upon powering the console. So I'm assuming that should be replaced at the bare minimum but I will stil lhave to wait for the o-scope to test the other ICs. I did bypass the BIOS by lifting up pin 20 of IC3 and cutting the trace from pin 13 of the card edge then soldering to pin 1 of the IO.

Maraakate wrote

I did notice that that 315-5214 gets hot almost instantly upon powering the console. So I'm assuming that should be replaced at the bare minimum but I will stil lhave to wait for the o-scope to test the other ICs. I did bypass the BIOS by lifting up pin 20 of IC3 and cutting the trace from pin 13 of the card edge then soldering to pin 1 of the IO.

The whole thing is probably so badly damaged that it may be worthwhile to just get a new one. The chips aren't connected in series so all chips got around 7V at once, and most can only handle 5.25V max. You could probably repair it but we are talking about replacing every chip on the board which is just a lot of manual labor.

When you don't even have $20 to buy another one and a stack of spare boards might as well you try this first.

Semi-back on topic here. Has a service/repair manual ever surfaced for the SMS?

I've never heard of one. The closest we have are the test ROMs like http://www.smspower.org/Games/ColorAndSwitchTest-SMS

That's weird. I wonder if Bock has something that's never been scanned in. Since the Test Cart exists for a repair tech the service manual would have to exist somewhere.

FWIW service manuals haven't been found for any Sega consoles from SG-1000 through Dreamcast.

I don't have anything that looks like a service manual.

Wow, not even Japanese ones? That's crazy! Even Vectrex has a heavily detailed and easy to follow service manual :-O.

Author	Message
Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	SMS Service Manuals? Posted: Sat May 12, 2012 7:00 pm
	slightly cross-posted I plugged an NTSC NES PSU (acros!) into one of my SMS' the other day and that killed it. I tried replacing the voltage regulator and I accidentally installed it backwards so now I have to find service manuals or something so I can test each component to find out which one bit the dust. It powers on but the screen is black and I remember I could feel one of the RAM chips getting hot so I'm sure it was probably one of those that got killed in the process. Is there a service manual for the SMS itself? If not, I know omp and few other fellows on here probably know what points to probe so I could find out what indeed failed. The caps all look okay, none look popped and I don't see any obvious blown traces (there was no smoke), etc.

TmEE Joined: 31 Oct 2007 Posts: 458 Location: Estonia, Rapla city	Posted: Sat May 12, 2012 8:20 pm
	Installing 7805 backwards will give the chips some 7V or more, it is quite like most of the chips are fried. Only survivor would be the RGB encoder chip and even that is unlikely. Without an o-scope you won't get far. Multimeter won't really show signs of life on various signals in the system. But you should replace the RAMs and other chips that get hot. I am not sure how practical is it though... Some big parts only come from another SMS.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Sun May 13, 2012 12:52 am
	Would it fry the first chip in the series and cut the flow to the others so they coudl be potentialyl spared? I think the RGB encoder might have survived because the screen will turn black. When it was installed backwards it showed some funny colours, etc on the screen. I do have a complete spare board and all the ICs are good on it. I was originally trying to do a no-BIOS mod on that one and I cut the wrong traces and I just never finished it. I just picked up an oscilloscope a few days ago. So, if you give me the proper points to probe we could figure this out. :)

TmEE Joined: 31 Oct 2007 Posts: 458 Location: Estonia, Rapla city	Posted: Sun May 13, 2012 7:50 am
	Good place to start are various CLK signals. CPU, subcarrier, Master, VDP etc. If any clock is missing you'll have problems. You did get black screen so at least Master and VDP clock should work. Then you can start looking at system data and address bus, when there is no activity on there you'll know the CPU is not functioning VDP will start with faulty VRAM but CPU won't. Also the BIOS ROM might be dead too, but you should still see activity on address bus at that point for a while.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Sun May 13, 2012 6:27 pm
	Is it as simple as locating the CLK pin on the IC and putting one probe on that and the other on GND? Never used o-scopes before so I will need some small hand-holding, heh.

TmEE Joined: 31 Oct 2007 Posts: 458 Location: Estonia, Rapla city	Posted: Sun May 13, 2012 9:01 pm
	Basically yes Choose approporiate time scale and voltage Center the line Probe. The longer the time scale the more you will see on the screen. There should be trigger option too, so toy around with it so it locks on to the waveform.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Sun May 13, 2012 9:49 pm
	Okay. It will be about a week or so before I can pickup the o-scope to do some tests. In the meantime, have you ever attempted the no-BIOS mod. One could get lucky, but I doubt it.

TmEE Joined: 31 Oct 2007 Posts: 458 Location: Estonia, Rapla city	Posted: Sun May 13, 2012 10:02 pm
	My SMS2 now has improved BIOS bypass which uses both !CARTCE and !BIOSCE for the cartslot. If it didn't then my SMS stuff will not function as I take over the memory control register.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Sun May 13, 2012 10:12 pm
	I'm going to try it on an SMS1. The 'parts' SMS1 I have was from a failed no-BIOS mod. I probably cut the wrong trace or something or other. That's why I wanted confirm if someone has done it with an SMS1. I'll just need to double check carefully as I do everything.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Sun May 13, 2012 11:57 pm
	I did notice that that 315-5214 gets hot almost instantly upon powering the console. So I'm assuming that should be replaced at the bare minimum but I will stil lhave to wait for the o-scope to test the other ICs. I did bypass the BIOS by lifting up pin 20 of IC3 and cutting the trace from pin 13 of the card edge then soldering to pin 1 of the IO.

Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	Posted: Mon May 14, 2012 5:52 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	Maraakate wrote I did notice that that 315-5214 gets hot almost instantly upon powering the console. So I'm assuming that should be replaced at the bare minimum but I will stil lhave to wait for the o-scope to test the other ICs. I did bypass the BIOS by lifting up pin 20 of IC3 and cutting the trace from pin 13 of the card edge then soldering to pin 1 of the IO. The whole thing is probably so badly damaged that it may be worthwhile to just get a new one. The chips aren't connected in series so all chips got around 7V at once, and most can only handle 5.25V max. You could probably repair it but we are talking about replacing every chip on the board which is just a lot of manual labor.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Mon May 14, 2012 5:59 pm
	When you don't even have $20 to buy another one and a stack of spare boards might as well you try this first.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Tue May 15, 2012 12:27 am
	Semi-back on topic here. Has a service/repair manual ever surfaced for the SMS?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 8984 Location: London	Posted: Tue May 15, 2012 8:31 am
	I've never heard of one. The closest we have are the test ROMs like http://www.smspower.org/Games/ColorAndSwitchTest-SMS

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Tue May 15, 2012 4:54 pm
	That's weird. I wonder if Bock has something that's never been scanned in. Since the Test Cart exists for a repair tech the service manual would have to exist somewhere.

Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	Posted: Tue May 15, 2012 10:35 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1012	FWIW service manuals haven't been found for any Sega consoles from SG-1000 through Dreamcast.

Bock Site Admin Joined: 08 Jul 2001 Posts: 6320 Location: London, UK	Posted: Tue May 15, 2012 11:53 pm
	I don't have anything that looks like a service manual.

Maraakate Joined: 05 Jun 2010 Posts: 544 Location: Pennsylvania, USA	Posted: Wed May 16, 2012 12:16 am
	Wow, not even Japanese ones? That's crazy! Even Vectrex has a heavily detailed and easy to follow service manual :-O.

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