Four Super Nintendos with Black Screen Problem - Trying to Fix

Discussion in 'Repair, Restoration, Conservation and Preservation' started by brento1138, Apr 19, 2015.

  1. jonoghue

    jonoghue Active Member

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    i've heard people say it's probably either the ram or the ppu but since there's no sound i doubt it's the ppu. my assumption is that it's the ram but since it says nintendo on it i was under the impression that it's a custom chip and is irreplaceable. and i don't want to steal one from a working SNES... i can solder ok but i don't want to risk damaging my personal SNES.

    anyway i'll double check if i can find the chip online.
     
  2. Bad_Ad84

    Bad_Ad84 The Tick

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    You doubt it, based on your superior electronics knowledge?

    Or just because some other people had a problem that is similar to yours, but could be caused by LOADS of different things but it happened not to be that for them?

    Caps fail with age, they also have a habit of leaking and causing tracks to get eaten. I wouldnt hold much stock in what random people with unknown soldering/electronics knowledge do/say.

    WIth something failing out of the blue, but just being stored for a long time - caps are the likely suspect. Electronics trouble shooting is all about ruling things out and you start with the most likely/obvious.
     
  3. jonoghue

    jonoghue Active Member

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    quite right. i guess i'll have to bite the bullet and buy new capacitors. just afraid of it not making a difference. in your opinion do you think bad caps could cause that image? again most games it's just a black screen but a certain few do things like that.
     
  4. citrus3000psi

    citrus3000psi Housekeeping, you want towel?

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  5. jonoghue

    jonoghue Active Member

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    scratch that, i was referring to the S-WRAM. for VRAM this one has 2 panasonic chips, MN44256S-10LL. but again since there's never any sound i don't think that's the case.

    oh thanks i thought they were twice as much for some reason. i'll order one.
     
    Last edited by a moderator: Aug 11, 2015
  6. Bad_Ad84

    Bad_Ad84 The Tick

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    COULD? yes
    IS? do not know, you have the machine and need to find out. Caps are cheap, easy and would need doing anyway
     
  7. jonoghue

    jonoghue Active Member

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    valid point. now in case that doesn't work do you think it could be the VRAM like CkRtech suggested? i don't think it is because again there's never any sound (based on my not-so superior electronics knowledge) so my guess would be if it's indeed a chip it's the CPU or WRAM, and i have a feeling the custom nintendo chips might not be as reliable as brand-name chips.
     
  8. Bad_Ad84

    Bad_Ad84 The Tick

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    reasoning for ruling out the vram sounds reasonable, but it could still cause trouble if it shares a bus with something else that would stop the console from booting.

    But I would replace caps (and inspect for trace damage under/around them) first
     
  9. CkRtech

    CkRtech Spirited Member

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    I once had a bad reset line connection to the sound processor in my machine. That would cause first SNES boot to sometimes not work and reset switch to always not work (sound processor would try to continue processing while the rest of the system would reset, resulting in a freeze).

    As Bad_Ad84 mentioned, you could replace the caps just to eliminate that variable. They are cheap, don't take long to replace, rule out a variable, and are there for harvesting for another SNES should you decide to move on from this unit.

    Favorite drink, fun music, a multimeter, and some new caps? :D
     
  10. jonoghue

    jonoghue Active Member

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    that's my next course of action. already ordered a set of new caps.

    now for future reference, i'm wondering if those VRAM chips are a fairly standard chip. i ask because the two SHVC SNESs i have both have different brand chips for the VRAM, but i couldn't find them online. console5 says it's SRAM 256Kb: 32K x 8-bit, and includes a pinout. i found this http://ebay.to/1UzGZQk and i'm wondering if it would work if i replaced the VRAM with it. looks the same, pinout is the same, is it more complicated than that or could i just hypothetically swap one out for the other?
     
  11. jonoghue

    jonoghue Active Member

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    Replaced all the electrolytic caps, no change whatsoever.
     
  12. CkRtech

    CkRtech Spirited Member

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    Did you do a continuity check to the ram chips?
     
  13. jonoghue

    jonoghue Active Member

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    i checked continuity between the CPU and cartridge connector, and between the S-WRAM and CPU.
    Got excited because i thought i found an open trace, but it turned out the schematic on console5.com had a mistake in it. it showed two pin 3's on the S-WRAM...

    i'll check the PPUs and VRAM later
     
    Last edited: Aug 14, 2015
  14. CkRtech

    CkRtech Spirited Member

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    Oh. If you could, send Luke a message by using the contact form on console5.
     
  15. jonoghue

    jonoghue Active Member

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    now this is weird... the schematic on console5 is copyrighted 1992 electronix corp. I can't believe that this 23 year old schematic that has probably been used countless times could actually have such a simple mistake in it.

    this schematic
    http://console5.com/techwiki/images/7/75/SNES-Schematic-CPU-Controller-Ports-RAM.png
    says D5 is pin 51 on the cartridge connector, pin 65 on the CPU, and pin 3 on the SRAM. but it also
    says A9 is pin 8 on the connector, 3 on the CPU, and.....3 on the SRAM. i've double checked that those buses aren't for some reason connected, and that it should be pin 24 on the SRAM.
     
    Last edited: Sep 21, 2015
  16. CkRtech

    CkRtech Spirited Member

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  17. jonoghue

    jonoghue Active Member

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  18. jonoghue

    jonoghue Active Member

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    After talking with someone on another thread who has EIGHT of these SHVC models that don't work, everything seems to point to the CPUs. i started wondering if maybe the first model had a CPU with some kind of flaw in it, which was corrected in later revisions, since it seems like this has been happening long enough to start effecting later models. i looked in both my dead SHVC models and they had "CPU A" in them. my SNS-CPU-GPM-02 has a "CPU B" in it. Can't tell for sure for another year or two, but i really think this is the problem. if i can somehow get a hold of a CPU i'll try replacing it.
     
  19. jonoghue

    jonoghue Active Member

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    well i got too curious about whether or not it's the CPU i tried taking a CPU from a working SNES (sacrilege, i know) and put it in one of the dead SHVC SNESs i have (the one i replaced the caps in). after several hours and an abysmally poor soldering job (lifted 3 contacts on the board, had to solder wires to the pins), i was certain that there was no way it would ever work. just about had a heart attack when star fox actually started on it. so the problem was definitely the CPU.
     
    MaxWar likes this.
  20. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    SMH about cannibalizing a working SNES. BUT GREAT WORK NONE THE LESS!! Did you remove the cpu with hot air or iron? ( if you used iron im not sure wheter to be horrified or impressed )

    So It was the CPU as we suspected. It is likely the same problem for most of these SNES. Repairing them will be hard without spare CPUs. The chinese IC ressellers have them apparently ( or so they claim ) but they either ask too much for them, or they are super shady and want you to pay with western union.
     

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