Super Nintendo - Unique problem - Page 1
Forum section: electronics / beginners

author: Raellz
author_rank: Contributor
timestamp: January 03, 2016, 03:46:12 pm
content: I've been trying to troubleshoot a Super Nintendo Motherboard all night and after replacing all the caps, testing for shorts and reading a lot of forum posts I decided to lift Pin 4 on the lockout chip and then tie it to ground. This has worked, to a degree. One of my games work, while another does not. When using the one that does work, the system updates the video about once every 2 seconds or so making title screens take half an hour. The sound usually works and is not slowed down at all.I put some of the original caps back in after testing them on the multimeter. I'm no expert, but I'm wondering if it is a bad cap still since... and forgive this comparison... but if you change the capacitors in a 555 circuit then you change the cycle of the output, such as blinking an LED faster or slower. I only got this far after lifting pin #4 on the lockout chip so I don't know what my next step should be.Has anyone heard of this problem or know how I can resolve it? Thanks.

author: Simon
author_rank: Unknown
timestamp: January 03, 2016, 03:55:13 pm
content: what was the failt in the first place ? caps these days won't be controlling clock spedds or anything like that. It will be a crystal clock.

author: Raellz
author_rank: Contributor
timestamp: January 03, 2016, 03:59:20 pm
content: Quote from: Simon on January 03, 2016, 03:55:13 pmAh, I forgot to mention that =/ It was a black screen with no static and no sound. The signal was picked up by my TV, but it went straight to black.

author: amyk
author_rank: Super Contributor
timestamp: January 03, 2016, 04:03:18 pm
content: I'm not familiar with the hardware but a timer running at the wrong frequency could cause the symptoms you're describing. There's a schematic here:http://wiki.superfamicom.org/snes/files/snes_schematic_color.pngYou can find the clock crystals and check them. It seems the sound is based on a separate crystal (24.576MHz) than the rest of the system (21.47727MHz, 6x NTSC colourburst), which is why it could remain operational.There are also test ROMs available. If you can find a cartridge to put it on, that might be a good option.

author: Raellz
author_rank: Contributor
timestamp: January 03, 2016, 04:17:23 pm
content: Quote from: amyk on January 03, 2016, 04:03:18 pmThat link doesn't seem to work. Is this the same thing?http://wiki.superfamicom.org/snes/show/Schematics,+Ports,+and+PinoutsI'm currently looking into how to make a test cartridge.So should I check the crystals?

author: stmdude
author_rank: Frequent Contributor
timestamp: January 03, 2016, 04:50:17 pm
content: Check the crystals. If you have access to an oscilloscope, you can probe one of the pins of the crystal and you should see the oscillations in the frequency specified on the schematic. ( Yes, it's the same schematic you linked you. Apparently, they don't allow direct linking)However, that's a really wierd failure scenario for a SNES. I've repaired _tons_ of them, and haven't seen a "slow" SNES ever. Plenty with the black screen, but I don't think any of them had sound either.Anyhow, I'm hoping you did the obvious things before jumping to caps? As in, cleaning the cartridge connector, as well as lifting it up, and cleaning the connector-to-the-connector (or whatever it's called). Some might require re-tensioning of the "blades" in the connector as well, depending on how its been used.This easily fixes 9 out of 10 SNESes that passes by my desk..Also, verify the output from the 7805. I've seen a few of those go bad as well, and cause wierd and wonderful failure modes.

author: Raellz
author_rank: Contributor
timestamp: January 03, 2016, 05:21:07 pm
content: Quote from: stmdude on January 03, 2016, 04:50:17 pmI do not have access to an oscilloscope unfortunately. I have cleaned all the connections and checked the solder points. I reattached the lockout chip's pin #4 to it's original position, now that I see it was already at groundSame issues still.I tested the 7805 and the results were 10.7v on the left pin and 5.02 on the right pin. According to what I'm reading, the left pin should be a couple volts less than the output of the power supply. I'm using the original SNES power supply which is 10v 850ma that works fine on all other SNES systems. Does this sound like a bad 7805? EDIT: Nah, it makes sense to me now. I been up all night so I'm not thinking right, haha. The 7805 seems good. Now I'm back to suspecting the caps.

author: marshallh
author_rank: Unknown
timestamp: January 03, 2016, 07:34:09 pm
content: 99% chance it's the cartridge connector. Always is. One time though I did see a bad WRAM (128k PSRAM).Timing is via crystal, though it is varactor-tuned. If you get a color video signal at any point that is fine (It will mostly affect the NTSC colorburst which is a bit sensitive)

author: stmdude
author_rank: Frequent Contributor
timestamp: January 03, 2016, 07:47:00 pm
content: Quote from: marshallh on January 03, 2016, 07:34:09 pmYup, seen WRAM as well as VRAM failures, but they are rare. I've also seen mod-chip installations that have deteriorated over time.Busted internal fuse is not unheard of either.I've actually never seen a broken trace, even though some of the systems I've repaired looks like they've been stored in a submarine.If you know your pseudo-history, you'll appreciate that I've never seen a soda-spill on/in any of the systems I get to see either (European SNES and Super Famicom).By the way. You guys are american. I actually haven't got an North-American Super Nintendo. Anyone want to trade cases with me? I've got plain-old european ones, as well as Super Famicom ones. No need to ship the electronics. They're the same.

author: marshallh
author_rank: Unknown
timestamp: January 03, 2016, 08:04:45 pm
content: Quote from: stmdude on January 03, 2016, 07:47:00 pmTrust me, you don't want 'em... It's garbage. Though, if you want a sickly yellowed one, those are easy to get.

author: stmdude
author_rank: Frequent Contributor
timestamp: January 03, 2016, 08:15:34 pm
content: Quote from: marshallh on January 03, 2016, 08:04:45 pmWell, they're unique garbage at least.It would look nice next to its brethren over here..

author: Raellz
author_rank: Contributor
timestamp: January 04, 2016, 05:53:59 am
content: Quote from: marshallh on January 03, 2016, 07:34:09 pmI get color video. It just slowly updates the video.

author: poot36
author_rank: Frequent Contributor
timestamp: January 04, 2016, 06:44:06 am
content: The 21.4Mhz clock is fed into the CPU, PPU1 and the cartridge slot. It exits the CPU at I think around 4Mhz or 2Mhz depending on what the game tells the CPU to output. This then goes to PPU2 and another pin on the cartridge slot. If you have a frequency counter you could check this. What version of SNES do you have? If it is the first version then the clock generation circuit will be different from the aforementioned schematic and there is a separate 8Mhz clock for the CIC (lockout chip). If your multimeter has a frequency function see if it will read the clocks correctly. I am beginning to suspect a bad CPU or solder joint. When I get to my computer with the schematic on it I will double check what I posted is correct.

author: Raellz
author_rank: Contributor
timestamp: January 04, 2016, 07:55:54 am
content: Quote from: poot36 on January 04, 2016, 06:44:06 amSHVC-CPU-01 (1990) is the SNES model.My multimeter does have Hz, but I'm not sure how to test what you're talking about. What do I probe exactly?

author: Raellz
author_rank: Contributor
timestamp: January 04, 2016, 01:21:18 pm
content: I removed the crystal then added another one, 16k, didn't start up. I put it back then swapped some capacitor values to see if anything would change, they did not. I then decided to reflow everything on the board and I still have the same slow video issue. I looked for solder bridges both before an after reflowing. I guess it's just a bad IC at this point

author: poot36
author_rank: Frequent Contributor
timestamp: January 05, 2016, 05:01:49 am
content: Ok, I screwed up. The 21.4Mhz clock goes to the CPU, and both PPU1 and PPU2. The slower SYSCLOCK goes to the SRAM for the CPU and the cartridge slot. I have attached the correct partial schematic for the version 1 SNES that includes the main clock generator circuit and the CIC (lockout chip) circuit. One of the resistors in the clock generator circuit is wrong but I do not remember which on (I think it is R4). To use your multimeter to measure the frequency set it to the Hz setting and connect the negative probe to any grounded part on the SNES (I prefer the metal band surrounding the front of the SNES) and the positive probe on the pin that has the clock signal you are trying to measure in this case pin 57 of the cartridge slot for the SYSCLOCK (the slow one) and pin 1 of the cartridge slot for the 21.4Mhz clock. I would also check also that all reset pins are at 5V (no lower then 4.3V) or thereabouts to prevent random reseting of various components. You can also check out the websitewww.NESDev.comfor additional help. That is how I figured out that my SNES had two bad registers in the CPU that was causing it to crash trying to play any normal game. I also wound up buying a logic analyzer for that as well (I already had a oscilloscope). You can view my adventures in that discovery here:http://forums.nesdev.com/viewtopic.php?f=12&t=13088.If anybody in Calgary has a broken SNES that has another fault (bad RAM, PPU1, PPU2) that the CPU is fine I would be interested in the CPU to fix my SNES.

author: true
author_rank: Frequent Contributor
timestamp: January 08, 2016, 05:22:36 am
content: The PPU was known for an odd assortment of failures.Does the game actually play at this reduced speed, or does video output just sporadically work? If the latter, you probably have a bad PPU.

author: Mephitus
author_rank: Regular Contributor
timestamp: January 08, 2016, 11:02:52 pm
content: Actually, it could be even simpler. What is the game? Several have alternate processors on them that could be causing a problem. Especially if other games work properly. Also, Raellz, what state do you live in? If you are in utah, you are welcome to use my scope.

author: Raellz
author_rank: Contributor
timestamp: January 23, 2016, 02:32:44 am
content: Quote from: Mephitus on January 08, 2016, 11:02:52 pmI have Super Mario World 2: Yoshi's Island which does not play at all and I have Super Ghosts n Ghouls. SGnG works at the first logo screen, but updates very slowly. Sound plays without issue. Once it's beyond that first title screen the video goes crazy. Random textures, but the movement of the textures is correct, just not the textures themselves.I'm in Kansas, but I appreciate the offer!Sorry for the lack of updates. I've replaced the crystal and all the caps then double checked that the caps are good, still nothing.

author: Raellz
author_rank: Contributor
timestamp: January 23, 2016, 02:37:35 am
content: Quote from: true on January 08, 2016, 05:22:36 amIt plays at the title screen, but I haven't tried using a controller yet. The textures are all broken though.

author: Raellz
author_rank: Contributor
timestamp: January 23, 2016, 02:39:25 am
content: Quote from: poot36 on January 05, 2016, 05:01:49 amThanks very much! I will give that a shot. I'm still really new to this, but I've fixed a few things before. I'm not sure what a logic analyzer is. I'll look that up.

author: Raellz
author_rank: Contributor
timestamp: January 23, 2016, 03:07:25 am
content: Quote from: poot36 on January 05, 2016, 05:01:49 amAlright I tested it a few times (while turned on of course) and I get 0.00 back on the Hz setting. Flipping over to Voltage I get 3.1 mV from pin 57, but that's all.I tested pin 1 and I got 21.47 khz (Edit: Mhz not Khz) so that's good.The reset pin gives me a whopping 314 mV. Well under the 5v target.We've narrowed it down!Now what can I do about that?

author: poot36
author_rank: Frequent Contributor
timestamp: January 24, 2016, 05:27:13 pm
content: Wait Khz or Mhz? If it is khz your meter probley cant read this high and is reading a harmonic of the frequency (mine read 300 Hz!). On pin 57 on my SNES with my meter set to DC volts I got 2.3V or so (my meter on on Hz mode read 29 Khz because it cant read this high). The reset pin on the cartridge slot should not be below 4.3V so yours is currently in reset. You must preform the tests with a cartridge in the slot or else the CIC (lockout) chip will keep the SNES in reset unless you disable the CIC chip. Because your SNES is currently in reset you will not get a signal on pin 57 as this is controlled by the CPU.

author: Raellz
author_rank: Contributor
timestamp: January 24, 2016, 09:56:49 pm
content: Quote from: poot36 on January 24, 2016, 05:27:13 pmMy mistake, Mhz. 21.47 Mhz oscillating crystal is what I installed and that's what it reads.I did the test with a cartridge in and I got just over 5 volts on the Reset pin and I got 2.729 Mhz on pin 57.I found this information on the SNES CPU specs. What I'm getting off that pin seems to be about the same speed as the "slow access" speed for the ROM and RAM. How would I go about testing the "quick access" speeds? I'm a newbie, but I assume I would check the Hz between the CPU and the RAM?"The SNES's CPU is a 65c816 based processor. While its clock speed is at about 21 MHz, it's effective speed is considerably lower, at 3.58 MHz for quick access (i.e. hardware registers at $2100-$21FF in banks $00-$3F), 2.68 MHz for slow access (i.e. ROM and RAM) and 1.79 MHz for very slow access."

author: poot36
author_rank: Frequent Contributor
timestamp: January 25, 2016, 12:06:11 am
content: Those are way better readings. To test fast access you need a cartridge that uses fast access rom chips. The speed of that clock signal is programmed by the code in the game so only some games used the faster speed. At this point I think you will need to make a test cartridge with a simple program on it to verify the basics of the SNES are working correctly. Find a cheap game that you can take the non re- programmable rom chip out of and place a re-programmable chip in a socket to run various test programs. Try and find a Lo-rom based game not a Hi-rom game as this will make loading code a lot easy'er for you. I made that mistake and was restricted to 32Kb programs not fun. You will have to rewire the cart to use a standard eeprom chip as the orignal rom chip pinout is nonstandard. You will also need an eeprom programmer as well. Good luck on fixing the SNES. The most likely reason Super Mario World 2: Yoshi's Island does not work at all is because it uses what is called the super fx chip which uses all of the cartridges pins and directly ties into the SNES's graphics chip. If any of the connections are bad ore the graphics chip is not working correctly the game will not play. Super Ghosts n Ghouls does not use this super fx chip so it has a higher chance of running correctly even on a broken SNES. If you could make a video of the corruption you are seeing that would be nice.

author: Kappes Buur
author_rank: Regular Contributor
timestamp: January 25, 2016, 04:38:29 am
content: I would add this diode

author: poot36
author_rank: Frequent Contributor
timestamp: January 25, 2016, 06:04:34 am
content: I have tested the SNES with just 5V on the output of the regulator and it did not damage the regulator. I got around 2V to 3V on the input of the regulator and distorted sound out of the SNES (the audio op-amps are run from the 10V input that is regulated down to 9V by the transistor). I believe that the regulator has a built-in protection diode. I don't think that there are many SNES's that have had the regulator fail due to a reverse voltage input.

author: Mephitus
author_rank: Regular Contributor
timestamp: January 25, 2016, 03:09:46 pm
content: Quote from: Raellz on January 23, 2016, 02:32:44 amYoshi's island uses the FX2 chipset and GnG does not. So you may want to take that into account for your troubleshooting as games that use the FX and FX2 chipset access the system resources differently. Admittedly, I have never had to repair a system that far gone.

author: Raellz
author_rank: Contributor
timestamp: January 26, 2016, 01:34:37 pm
content: Quote from: poot36 on January 25, 2016, 12:06:11 amThanks.I'm going to have to do a lot of research on making my own test cartridge. I've been told I should do it before. The most experience I have on this subject would be programming an Atmega328 for an Arduino and that's kid stuff.I will make a video for it soon and post a link.

author: Raellz
author_rank: Contributor
timestamp: January 27, 2016, 04:34:38 am
content: Quote from: poot36 on January 25, 2016, 06:04:34 amHere is video of what it is doing.

author: poot36
author_rank: Frequent Contributor
timestamp: January 28, 2016, 03:18:19 am
content: Ok, I think this is where we stand currently:CPU: PassWRAM: PassData Bus: PassAddress Bus: PassCIC (Lockout chip): PassAPU (Audio Processing Unit): PassPA Bus: ?? <- probably ok but Yoshi's Island did not work so unsurePPU1: ?? <- this basically loads the data into the VRAM (think shift register)VRAM: ??PPU2: ?? <- grabs data from VRAM and displays itThe start up logo looked mostly ok but it did display very slowly (as did the rest of the game as well as corrupted graphic tiles).I would check the reset lines going to the PPU1 and PPU2 chips just to make sure they are working. Keeping in mind that PPU2 sends out 2 reset lines of its own. You could also try grounding one of the data or address lines on the VRAM chips with a 100 ohm or so resistor (or your meter on the ma range) and see what happens. You can do this test when the cart is in the SNES and it is running. You could also take the cart out and see if any of the data or address pins on the VRAM are being held high or low as that would indicate potential bad RAM. This test may produce unpredictable results depending on how the SNES chips hold the VRAM in a reset condition. I have attached a very simple test rom for you to use when you make a flash cart. The made tiny one is for a hi-rom cart if that is what you manage to get to make your flash cart. Make sure to copy and past any rom files you use to test if they are smaller then your eeprom or eprom chip until they are the same size as the chip you are trying to fill. I recommend using notepad ++ and using s special copy feature so as to not introduce any extra data from the copy and pasting that may need to be done.

author: Raellz
author_rank: Contributor
timestamp: January 28, 2016, 01:38:43 pm
content: Quote from: poot36 on January 28, 2016, 03:18:19 amRgr. I've been looking up test cartridges, but I still have no idea how to make one. All I can find is information about people using the official ones. How did you make yours?I really appreciate the effort you're putting into helping me with this.

author: poot36
author_rank: Frequent Contributor
timestamp: January 29, 2016, 04:10:19 am
content: I made mine out of a cart with a dead rom chip. I removed the rom chip and installed a socket (had to rewire the PCB because the rom chip pinout is different from a standard eeprom chip). I used a old eeprom chip from a P2 motherboard and programed it with a eeprom chip programmer (a old Data I/O unisite from 1988 running software from 2006!). Here is a link to the SNES carts rom pinout:http://www.caitsith2.net/snes/flashcart/cart-chip-pinouts.htmland I have attached the datasheet for the eeprom chip that I used (the pinout on all standard 2Megabit chips should be the same). I had to rewire 4 pins and disconnect the Write Enable (WE) pin on mine to get it to work.So here is the list of things you will need:eeprom chipbroken or cheap SNES cart32 or 36 pin socketeeprom programmer

author: Raellz
author_rank: Contributor
timestamp: January 29, 2016, 10:24:46 am
content: Thanks so much.Is this the eeprom?http://www.ebay.com/itm/W29C020-90-DIP-32PIN-WINBOND-29F020-256Kx8-FLASH-MEMORY-/331761247120?hash=item4d3e82e390:g:FsgAAOSwoydWmB3OCan I program it with a Pickit 2 or 3? I've been thinking about getting one, but I'm not entirely sure what they can do yet besides program some chips. I don't have a Data I/O programmer =/ Would I be able to perhaps use a breadboard, a 32 pin socket, jumper wires and the Pickit to program the eeprom? I've done that to program a few Atmega328s, minus the Pickit. I hope that doesn't sound too funny, but I'm a newbie who is delving into things way out of his league... but I'm determined and having fun.Does it matter if the cart I use doesn't have the full amount of pins or will the eeprom still access the full features of the SNES hardware?

author: poot36
author_rank: Frequent Contributor
timestamp: January 30, 2016, 04:30:26 am
content: Yes that is the eeprom but you do not have to get that one it was just an example. The minimum size I would recommend getting is a 1 Megabit. Just choose the cheapest one that is that size (or bigger) and has 32 or 36 pins. The Pickit is for programming microcontrollers and serial eeproms not parallel eeproms. Most (if not all) SNES carts should have the 36 pin socket but there are some games that have more then one eeprom chip in them and you want to avoid them as well as any carts that use an accelerator chip (eg Super FX chip, Mario chip) this carts have the extra two cart connector tabs on the bottom have a look at your Super Mario World 2: Yoshi's Island game for an example of this. Just try and find a sports game they should be cheap. Don't worry if any of your questions sound funny all of us were at that point sometime in our lives as well. My re-programmable cart did not work first time either (I miscounted the pins and cut the wrong traces to rewire it!) For the eeprom programmer I would look at Kijiji, Craigslist, or eBay just make sure it supports the eeprom you are trying to program.

author: Raellz
author_rank: Contributor
timestamp: January 30, 2016, 07:22:57 am
content: I'm looking at the TL866CS Uni Programmer and it says this"The chip supporting range?All kinds 26 27 28 29 37 39 49 50 Parallel ROM, EPROM, EEPROM" What is this referring to for compatibility?After some digging I found this listhttp://www.autoelectric.cn/minipro/miniprosupportlist.txtwhich shows a huge list of compatible chips, yay!It says the W29C020 is compatible, but the chip I was looking at has a -90 at the end and I cannot find that on the list. Does that matter at all?

author: poot36
author_rank: Frequent Contributor
timestamp: January 30, 2016, 02:48:35 pm
content: That programmer should work as long as there are drivers and software for you version of operating system on your computer and your computer has the appropriate connection for the programmer. The -90 means the access speed of the eeprom chip. It should work just fine at lower speeds as well. For the SNES the high speed access is -120ns and low speed access is -200ns so this chip is faster then either of these speeds so it will work just fine.

author: Raellz
author_rank: Contributor
timestamp: January 31, 2016, 08:22:36 pm
content: Quote from: poot36 on January 30, 2016, 02:48:35 pmThanks so much. I'm going to have to think if I want to invest into one of those so it will be a little while before I have any updates probably.

author: poot36
author_rank: Frequent Contributor
timestamp: January 31, 2016, 09:26:08 pm
content: I got my programmer locally (off Kijiji) for free. If you wait you may be able to do the same thing. Also check out any swap meets as well.

author: Raellz
author_rank: Contributor
timestamp: February 02, 2016, 12:58:28 pm
content: Quote from: poot36 on January 31, 2016, 09:26:08 pmThanks I'll do that.