Replacing SRAM on a SNES console

[Ged]

Hi guys.

I have an SHVC-CPU-01 american snes that started showing garbled graphics. I used the console for years without problems, but then it went through some pretty quick power ON and OFF cycles due to a faulty connection in the power plug, so I'm guessing this is the cause.

The games plays perfectly, but the backgrounds are often messed up. I'm sure it's console-side because I tried the games on other systems.
On Donkey Kong Country the garbling is really bad and persistent, but the weird thing is that with Super Metroid and Mega Man X,the backgrounds are fine until I enter the pause menu, then I go back to the game and the background is all messed up.
This made me think it could be a SRAM issue, so I'd like to try to replace it. I heard it should be fairly easy, and it's pretty much the only thing I can do before giving up, 'cause I don't think I would be able to replace the PPU (and probably it's not even worth it).

The problem is that I know pretty much nothing about ICs, could someone point me to a suitable replacement?

Thanks!

Pic of the board: https://ibb.co/j9Cd4y

[NoAffinity]

Assuming U4 and U5 are the ones you're wanting to replace, replacement chips seem to be pretty easily attainable:

https://www.google.com/search?source=hp ... -b20OPtsBI

Is there something else you need to know?

[Ged]

Assuming U4 and U5 are the ones you're wanting to replace, replacement chips seem to be pretty easily attainable:

https://www.google.com/search?source=hp ... -b20OPtsBI

Is there something else you need to know?

Yeah I searched for those but it seems like they're only available in stocks of 3000 or more units..is there a more easily sourcable alternative?
Also, I'm not sure those are the ones to be replaced, can you confirm that? Thanks

[NoAffinity]

This click-through was my first attempt, so figured all potential sources were the same. How about this one?

https://www.questcomp.com/part/4/LH5225 ... gn=AkType0

[Ged]

This click-through was my first attempt, so figured all potential sources were the same. How about this one?

https://www.questcomp.com/part/4/LH5225 ... gn=AkType0

They have a minimum order of 25$ . Do you think anything from this list would work? https://console5.com/wiki/SRAM_256Kb:_32K_x_8-bit

[NoAffinity]

This click-through was my first attempt, so figured all potential sources were the same. How about this one?

https://www.questcomp.com/part/4/LH5225 ... gn=AkType0

They have a minimum order of 25$ . Do you think anything from this list would work? https://console5.com/wiki/SRAM_256Kb:_32K_x_8-bit

This thread suggests that different sram's have been used and even the slowest 120ns should be much faster than the SNES needs. Taking from that, LH52A256N-10LL, MOSEL MS62256CL-10F0, MOSEL MS62256CL-10FC, SONY CXK58257AM-12L, SONY CXK58257AM-12L, KM62256ALG-10 and MN44256S-10LL were all used on SHVC-CPU-01.

However, it notes there were various other parts revisions which may or may not affect inter-compatibility. Based on the model noted there and associated components, other identical configurations used the following ram: KM62256ALG-10, SONY CXK58257AM-12L, LH52A256N-10L, or MOSEL MS62256CL-10F0. (Double check my cross-referencing, and check it against the components on your board).

https://forums.nesdev.com/viewtopic.php?f=12&t=15206

[Ged]

This click-through was my first attempt, so figured all potential sources were the same. How about this one?

https://www.questcomp.com/part/4/LH5225 ... gn=AkType0

They have a minimum order of 25$ . Do you think anything from this list would work? https://console5.com/wiki/SRAM_256Kb:_32K_x_8-bit

This thread suggests that different sram's have been used and even the slowest 120ns should be much faster than the SNES needs. Taking from that, LH52A256N-10LL, MOSEL MS62256CL-10F0, MOSEL MS62256CL-10FC, SONY CXK58257AM-12L, SONY CXK58257AM-12L, KM62256ALG-10 and MN44256S-10LL were all used on SHVC-CPU-01.

However, it notes there were various other parts revisions which may or may not affect inter-compatibility. Based on the model noted there and associated components, other identical configurations used the following ram: KM62256ALG-10, SONY CXK58257AM-12L, LH52A256N-10L, or MOSEL MS62256CL-10F0. (Double check my cross-referencing, and check it against the components on your board).

https://forums.nesdev.com/viewtopic.php?f=12&t=15206

All right thanks. So, I'm guessing you suggested the ones associated with PPU1 (01) and PPU2 (01), since I have those on my board. The problem is, I also have an S-CPU, not an S-CPU A, and it seems that this configuration is associated with LH52256N-90TL only. To recap, my components are:

S-CPU
PPU1 (01)
PPU2 (01)
LH52256N-90TL
BA6592F
..and I don't know about the capacitor yet, because I can't check the board at the moment.

I found this: https://www.ebay.it/itm/4pcs-LH52256N-9 ... SwIVhaNWtb. Can you perhaps tell if it is equivalent? I can't find the datasheet for the 90TL

[Syntax]

There's 2 Sram chips right? Why don't you swap them first and see if the issue changes before ordering new chips.

[Ged]

There's 2 Sram chips right? Why don't you swap them first and see if the issue changes before ordering new chips.

That's an idea! Will definitely try that

[mvsfan]

Another thing - when you get your new chips, replace one of them first and then turn the snes on. See if your problem clears up.

Ive done that, and only had to replace 1 of them before.

[Ged]

Another thing - when you get your new chips, replace one of them first and then turn the snes on. See if your problem clears up.

Ive done that, and only had to replace 1 of them before.

All right, thanks man. What chips did you use as a replacement and how did you pick them?

[mvsfan]

i just used the same sony chips i had in my console. i read the numbers off of them and ordered new ones on ebay.

[Ged]

i just used the same sony chips i had in my console. i read the numbers off of them and ordered new ones on ebay.

Yeah I couldn't find them at first, but then I found a site where you can ask for a quotation to a bunch of china based IC sellers, and I ended up ordering 2 for 12 USD shipped, which is not too bad. We'll see if it works.

By the way, I choosed not to swap the chips, because I already lifted a bunch of pads while desoldering them the first time, I don't want to do it again and risk even more damages I'll just solder the new ones and see how it goes.

[mvsfan]

the easiest way to remove those chips is to cut the pins on the old one then wipe them off the pads with your iron. no broken traces that way.

[unmaker]

I once bought a stash of severely yellowed and cracked SNES consoles in order to salvage their multi out connectors. About half of them had graphical issues so just for fun I tried fixing them. I did not have a hot air station at the time so I used one of these:

https://www.ebay.com/itm/350W-MINI-HEAT ... itleDesc=0

A heat gun is not ideal but I managed to make it work. In all cases replacing the SRAM did nothing and it was the PPU or CPU that needed replacing. Of course this is a small sample size so your case might be different. You could also try using the SNES Burn-In v1.03 rom which could narrow down possible issues.

You might find this page useful as well:

http://projectvb.com/nss/logs.htm

It shows various SNES issues and what needed replacing. A quote from this page: "-Statistics: While working with Super System and SNES motherboards, I came across 24 bad CPUs, 4 bad PPU1s, 4 bad PPU2s, 1 bad APU, and no bad WRAMs or VRAMs... if you suspect either a bad CPU or WRAM, I'd say odds are better that the CPU is bad." There is a typo there as I'm sure this person meant to say "either a bad PPU or WRAM"

[Ged]

I once bought a stash of severely yellowed and cracked SNES consoles in order to salvage their multi out connectors. About half of them had graphical issues so just for fun I tried fixing them. I did not have a hot air station at the time so I used one of these:

https://www.ebay.com/itm/350W-MINI-HEAT ... itleDesc=0

A heat gun is not ideal but I managed to make it work. In all cases replacing the SRAM did nothing and it was the PPU or CPU that needed replacing. Of course this is a small sample size so your case might be different. You could also try using the SNES Burn-In v1.03 rom which could narrow down possible issues.

You might find this page useful as well:

http://projectvb.com/nss/logs.htm

It shows various SNES issues and what needed replacing. A quote from this page: "-Statistics: While working with Super System and SNES motherboards, I came across 24 bad CPUs, 4 bad PPU1s, 4 bad PPU2s, 1 bad APU, and no bad WRAMs or VRAMs... if you suspect either a bad CPU or WRAM, I'd say odds are better that the CPU is bad." There is a typo there as I'm sure this person meant to say "either a bad PPU or WRAM"

Thanks for the useful infos. Yeah, it probably won't fix my issues, but it was the only thing I could try. If it doesn't work, I'll just wait to come across another dead SNES to salvage for the CPU (though I'll have to understand what is the compatibility on those..).

[mvsfan]

what about a bad 1-chip? how do you diagnose it? ive never found any schematics for it only the old snes.

[rama]

1Chip SNES commonly die when their S-APU chip fries. Just to make sure it's that, try a good handful of games.
A few games show some screens before they try to initialize the S-APU.

The only fix for this is replacement of the S-APU, unfortunately. And this is not a common chip, as every donor is usually another 1Chip.

[mvsfan]

the APU? thats audio processing unit right?

youd think it would just have no sound because of that but i guess theres some kind of self test that fails on boot.

thats funny because i have a 1-chip that only works with super baseball simulator 1000. that game runs perfect the rest dont.

at this point ive stopped looking for broken snes consoles because i am accumulating a stack that i cant fix.

Sega genesis and Nes seem to be way more reliable at this point in time. and if they dont work i can usually get them going again.

[rama]

Yep, S-APU combines the audio processing chips and audio RAM into one chip.
Games talk to the audio unit on bootup, usually before showing any graphics but sometimes after a logo.
If the APU doesn't respond, the game hangs there, waiting forever.

I managed to replace the S-APU with an old "can" audio module from a generation 1 SNES once.
The system worked well with it but the installation is messy and missing a soft reset feature.

[mvsfan]

well, thats great that the old shvc module works in the 1-chips. i wasnt aware it did. I think its time for a pcb to do that installation. something that solders to the expansion port you connected it to.

you can often find those SHVC sound modules on ebay seperate for a few bucks.

BTW, would the slimmed down Non-1chip boards like an APU version motherboard have that same 1-chip apu? I have quite a few of those boards too. id have to look for them. though. i think most just have broken multiouts or something and the sound chips are probably good.

[rama]

The "APU" mainboard revision appears to be quite rare, but yes, it has the required S-APU chip.
I don't know if they're a drop-in replacement, but they most likely are.

As for the sound module replacement, my proof of concept there is still lacking part of a reset circuit.
I think the S-APU has some kind of delayed reset signal that it needs to send to the CPU.
I faked it by manually sending the reset pulse so this part needs to be better before considering a PCB / adapter :p

[mvsfan]

is there a way you can test the apu to see if its bad?

[rama]

Yes, sure. As long as the chip is still on the board, simply try a few games and see if you get anything.
If only a few games start and they're consistently stopping at the same spot, it's almost guaranteed* to be the S-APU chip.
The SD2SNES menu works without the S-APU, if you have one.

*
I suppose it could be an oddball other IC or traces / soldering issue but that's very unlikely.
It could also be an external issue that prevents the S-APU from running, like a damaged resonator (the blue blob near the chip).
This is also unlikely though.