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Need help, SNES Gen 1 Video Repair more than 50 units RF Output OK, AV OUTPUT NOT OK! All of Them In Same Condition

May 18, 2017 at 4:08:22 PM
faramith (105)
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(Jerry Robles) < Eggplant Wizard >
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HI Guys, been in the videogame repair business for 15 years, but never figured out how to repair the Model 1 Super Nintendo that has AV Problems, so I just kept storing these up, so I am fed up with all these defects here, and need help to figure out whats wrong with them! and no, its not cap replacement, Ive done enough cap replacements on my snes to know this is not the problem!.  Ok so in a nutshell, all of them are Generation 1 SNES Consoles, the one with the removable soundboard, all of them work fine with RF Hookups but if you use an AV Cable a lot of jitter can be seen (And you can hear the sound ok) So I guess the snes has 2 video controller chips, of some kind, that outputs the video one thru RF and the other thru RCA. I need to know wich chip is it! and its damaged on all of my 50+ consoles, (95% of generation 1 snes that i get i trades have this damn problem).  Here are a few pics for you to see the problem, thanks again!

May 19, 2017 at 10:05:16 AM
Bratwurst (79)
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Seems like the person to ask would be Byuu since he dissected the SNES so thoroughly to make his emulator. Would you be interested in donating one of these defective units so that an interested party to poke around? I wonder if a workaround could be achieved by tapping into the RGB and externally converting it into composite/s-video.

May 19, 2017 at 6:27:17 PM
Nes Freak (31)
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(Dave ) < Ridley Wrangler >
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i have a snes control deck tester by Nintendo that could answer that problem.

May 19, 2017 at 8:30:57 PM
Pikkon (8)
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(スーパーファミコンコレクター ) < Meka Chicken >
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The snes video encoder uses rgb first then converts it to composite and such,I bet s-video acts the same.
I bet your snes's would look fine running rgb or a component mod.

Caps can be a problem but did you look for any broken traces,reflow any chips or replaced?

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May 20, 2017 at 4:16:36 AM
Nes Freak (31)
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another simple issue could be the connections in the back are dirty. with the n64 if the multi out get dirty weird things happen with the picture which resembles your pictures you posted. but like pikkon said you could have bad caps.

if that doesnt work theres anather thing you can try.  theres a pot at the front of the board if you take some electric oil or contact cleaner and spin it around that might fix the problem too.


Edited: 05/20/2017 at 04:18 AM by Nes Freak

Jun 27, 2017 at 2:18:10 PM
darkchylde28 (10)
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(Doug ) < El Ripper >
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There haven't been any responses to this thread since May, so I assume there's no update, but I figured I'd bump it just in case. I'm currently in this boat with my original childhood SNES. All contacts everywhere are clean and look good, no bulging or leaked caps, but I get RF video fine but no AV. The SNES that my aunt & uncle left me fires right up on AV without issue. Since I've got the secondary system to use, I'm not truly stuck, but I'd love to get my personal, childhood unit back up and running at 100% if at all possible.

-------------------------
Need Stadium Events + Panesian titles, 6-in-1's, Menace Beach, Moon Ranger & Secret Scout to complete my licensed/unlicensed sets.

If you've got any of the above for sale, hit me up!

Jun 27, 2017 at 2:47:12 PM
Guntz (115)
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< Master Higgins >
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Given the SNES's lack of capacitors and the content of this web page (http://projectvb.com/nss/logs.htm...), my money is on chip-level failure causing these problems of broken graphics and missing Multi-AV composite.

Just like Mask ROMs, processors can develop internal flaws or entirely fail.

Jun 27, 2017 at 7:53:30 PM
Bratwurst (79)
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As discussed on Digital Press, possibly the BA6592F or Q10 transistor in the video out line. I'd like to get ahold of one to tinker with myself to see if the issue could be resolved.

Jun 27, 2017 at 8:26:25 PM
Ichinisan (29)
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Originally posted by: Guntz

Given the SNES's lack of capacitors and the content of this web page (http://projectvb.com/nss/logs.htm), my money is on chip-level failure causing these problems of broken graphics and missing Multi-AV composite.

Just like Mask ROMs, processors can develop internal flaws or entirely fail.

Isn’t the RF circuit fed from composite? If so, there’s a good composite signal somewhere on that board.

I’m about to work on one that was reported to have similar issues. I think it’s also an early board with the modular sound processor.

Jul 3, 2017 at 8:59:10 AM
CZroe (31)
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Well, Ichinisan and I spent all day working on one of these RF-only SNES units and (SHVC-CPU-01) before we hit a different roadblock that pretty much stopped us from going any further. Even so, I'm pretty sure I found something noteworthy:
Pin 9 on the multi-out (Composite) is shorted to logic chips all over the rest of the board. It goes to pin 14 of U9, pin 18 of U8, both PPUs, WRAM, etc. I traced to places all over the board that still had continuity with pin 9 of the multi-out. That's definitely not right.

Another SHVC-CPU-01 board I have with a different problem gives me a quick beep when I check continuity and doesn't beep again until I reverse the probes, indicating that there is a capacitor or something that charges/discharges and not an actual short like the RF-only board. If it really isn't a capacitor (I should check to make sure none of the electrolytics are shorted), my guess is that the short is coming from one of the logic chips somewhere.

Salvaging from my other SHVC-CPU-001 board, I swapped Q10 and U7 (video encoder) but nothing changed. Q10 is the transistor connected to 5v on the underside near the RF module's 5v leg. It is part of the path between the video encoder's Pin 7 and the multi-out's pin 9.

I traced pin 7 from the encoder chip all the way to both the RF video input and pin 9 on the multi-out. It's hard to see through the bottom silkscreen where it branches, but it does.


Edited: 07/03/2017 at 09:01 AM by CZroe

Jul 3, 2017 at 9:22:07 AM
Pikkon (8)
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(スーパーファミコンコレクター ) < Meka Chicken >
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I have a SHVC-CPU-01 that would only display black and white on s video and composite but component was in color,swapped out the video encoder more than once and was the same problem,if I ever get around to it a ppu swap might be worth a try.


And CZroe,try and do a component mod or if you can do rgb you might get video.

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Edited: 07/03/2017 at 09:24 AM by Pikkon

Jul 3, 2017 at 10:52:00 AM
CZroe (31)
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Originally posted by: Pikkon

I have a SHVC-CPU-01 that would only display black and white on s video and composite but component was in color,swapped out the video encoder more than once and was the same problem,if I ever get around to it a ppu swap might be worth a try.


And CZroe,try and do a component mod or if you can do rgb you might get video.

It had the BA chip that doesn't do Component but I swapped in a Component-capable S-ENC chip. I had planned to do exactly that until I hit the other roadblock I was talking about.

In case something in the RF modulator was feeding back to cause it I tried removing that and I'm pretty sure that was the last thing I tested before hitting the unrelated roadblock that stopped me dead in my tracks (have to do another repair before I can continue). IIRC, I was swapping in the RF modulator from another SHVC-CPU-01 at that point.

Ichinisan had already traced multi-out pin 9 to U9 pin 14 before I even started looking at it and swapping known-good components, but he didn't know it wasn't supposed to have a connection there. U9 pin 14 is already supposed to be connected to all those other points I mentioned except multi-out pin 9. This means that the short between multi-out pin 9 and those points already existed before the new issue.

I'm very curious to know if the OP's boards are also all shorting multi-out pin 9 to those points (U9 pin 7, U8 pin 18, PPU1/2's 28th pins, whatever the U6 work RAM pin was, etc). If so, then we are likely onto something.


Edited: 07/03/2017 at 11:19 AM by CZroe

Jul 3, 2017 at 11:33:36 AM
CZroe (31)
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Originally posted by: Bratwurst

As discussed on Digital Press, possibly the BA6592F or Q10 transistor in the video out line. I'd like to get ahold of one to tinker with myself to see if the issue could be resolved.
Ah! It's nice to see that my logic lines up with theirs, but I tried swapping known-good parts for both of those and it didn't help. Wish I had seen this thread earlier because I traced my way to those same two components very tediously! Guess I should have looked at Console5's schematics, but it was getting late (~4AM) and I never ran out of stuff to pursue without them.


Edited: 07/03/2017 at 11:37 AM by CZroe

Jul 3, 2017 at 11:58:43 AM
Bratwurst (79)
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(Meat Meister) < Eggplant Wizard >
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Well done testing that theory out on your own though. I wonder if you're onto something with the RF modulator interfering with the composite out. I mean, it IS getting the signal to put out to coaxial in the first place, so...

Jul 3, 2017 at 12:08:42 PM
CZroe (31)
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Originally posted by: Bratwurst

Well done testing that theory out on your own though. I wonder if you're onto something with the RF modulator interfering with the composite out. I mean, it IS getting the signal to put out to coaxial in the first place, so...
Yeah, and the signal does take a separate path through other components to get there. Q10 is connected to voltage from the plane right next to the RF modulator's voltage pin so I wondered if there could be some resonate interference between the RF modulator and Q10. The other two leads on Q10 are part of the separate video path to the multi-out, so it seemed to be a logical component to look at. I considered removing it and bridging the video path without Q10 to see if I get stable, unamplified Composite, but I didn't get that far before something unrelated threw a monkey wrench into everything (have to take care of that before continuing).
 


Edited: 07/03/2017 at 12:13 PM by CZroe

Jul 3, 2017 at 8:39:13 PM
Pikkon (8)
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(スーパーファミコンコレクター ) < Meka Chicken >
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Originally posted by: CZroe
 
Originally posted by: Pikkon

I have a SHVC-CPU-01 that would only display black and white on s video and composite but component was in color,swapped out the video encoder more than once and was the same problem,if I ever get around to it a ppu swap might be worth a try.


And CZroe,try and do a component mod or if you can do rgb you might get video.

It had the BA chip that doesn't do Component but I swapped in a Component-capable S-ENC chip. I had planned to do exactly that until I hit the other roadblock I was talking about.

In case something in the RF modulator was feeding back to cause it I tried removing that and I'm pretty sure that was the last thing I tested before hitting the unrelated roadblock that stopped me dead in my tracks (have to do another repair before I can continue). IIRC, I was swapping in the RF modulator from another SHVC-CPU-01 at that point.

Ichinisan had already traced multi-out pin 9 to U9 pin 14 before I even started looking at it and swapping known-good components, but he didn't know it wasn't supposed to have a connection there. U9 pin 14 is already supposed to be connected to all those other points I mentioned except multi-out pin 9. This means that the short between multi-out pin 9 and those points already existed before the new issue.

I'm very curious to know if the OP's boards are also all shorting multi-out pin 9 to those points (U9 pin 7, U8 pin 18, PPU1/2's 28th pins, whatever the U6 work RAM pin was, etc). If so, then we are likely onto something.


All SHVC-CPU-01 can output component,you just need to build a amp for the Pr/Pb.
 

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Jul 3, 2017 at 8:41:58 PM
CZroe (31)
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(Julian Emmett Turner II) < Bowser >
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Originally posted by: Pikkon
 
Originally posted by: CZroe
 
Originally posted by: Pikkon

I have a SHVC-CPU-01 that would only display black and white on s video and composite but component was in color,swapped out the video encoder more than once and was the same problem,if I ever get around to it a ppu swap might be worth a try.


And CZroe,try and do a component mod or if you can do rgb you might get video.

It had the BA chip that doesn't do Component but I swapped in a Component-capable S-ENC chip. I had planned to do exactly that until I hit the other roadblock I was talking about.

In case something in the RF modulator was feeding back to cause it I tried removing that and I'm pretty sure that was the last thing I tested before hitting the unrelated roadblock that stopped me dead in my tracks (have to do another repair before I can continue). IIRC, I was swapping in the RF modulator from another SHVC-CPU-01 at that point.

Ichinisan had already traced multi-out pin 9 to U9 pin 14 before I even started looking at it and swapping known-good components, but he didn't know it wasn't supposed to have a connection there. U9 pin 14 is already supposed to be connected to all those other points I mentioned except multi-out pin 9. This means that the short between multi-out pin 9 and those points already existed before the new issue.

I'm very curious to know if the OP's boards are also all shorting multi-out pin 9 to those points (U9 pin 7, U8 pin 18, PPU1/2's 28th pins, whatever the U6 work RAM pin was, etc). If so, then we are likely onto something.


All SHVC-CPU-01 can output component,you just need to build a amp for the Pr/Pb.
Cool. Everything I read online said it had to have the S-ENC chip and not the BA chip, so I'm happy to hear otherwise.

Jul 3, 2017 at 9:01:40 PM
Pikkon (8)
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(スーパーファミコンコレクター ) < Meka Chicken >
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This one works just fine.
https://gbatemp.net/attachments/c...

When I did mine,I amped both pins and it came out great.

-------------------------


Jul 3, 2017 at 10:49:11 PM
CZroe (31)
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Originally posted by: Pikkon

This one works just fine.
https://gbatemp.net/attachments/comp-jpg.44482/

When I did mine,I amped both pins and it came out great.
Did yours have the BA chip? Even that guide says it has to have the S-ENC chip. Three of the four SHVC-CPU-01 boards I have here have the BA chips.

 


Edited: 07/03/2017 at 10:54 PM by CZroe

Jul 3, 2017 at 11:44:29 PM
Pikkon (8)
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Yup as they share the same pinout,if try to do it without a amp the colors will be very weak.

Here's the datasheet,forgot I had it on my pc.
https://www.mediafire.com/file/4t...

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Edited: 07/04/2017 at 08:15 AM by Pikkon

Jul 4, 2017 at 11:23:16 AM
CZroe (31)
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Originally posted by: Pikkon

Yup as they share the same pinout,if try to do it without a amp the colors will be very weak.

Here's the datasheet,forgot I had it on my pc.
https://www.mediafire.com/file/4t7lfth68a990ap/BA6592F.pdf

Yeah, but they are vestigial pins even on the S-ENC chip, since the console itself doesn't have Component. A revised chip can drop the output on those pins without issue since they were never actually used by the console. Heck, the SNS-101 dropped S-Video output on the multi-out (pin-compatible with the SNS-001 for Composite video), and that was actually in use!

Jul 6, 2017 at 11:08:35 PM
CZroe (31)
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Crap. The system I was working on had been recapped by the owner in an attempt to fix this problem. As we already know, that doesn't work for this issue. When I noticed continuity between multi-out pin 9 and places all over the system where there should not be a connection, I thought I was onto something, but it was actually just a short from a bad cap job.  

It turns out that this system had 5v feeding into multi-out pin 9 (Composite out). It took a while but I traced the short to a via under C58 that leads from the 5v plane to R19 on the bottom side. There was a small blob of solder on the via that was shorting to the negative side of C58. This is connected through R33 (56ohms) to multi-out pin 9 (Composite video), which explains how I measured 55ohms to chips all over the board from multi-out pin 9.

I pulled my RF modulator and S-ENC chip off the board to restore the originals but found that when I reinstalled those previously known-good parts into my SNES it now has the same problem except that the RF modulator also doesn't work. Audio only with standard AV, audio plus scrambled B&W video with S-Video, no audio or video with RF.

Crap. Well, that SNES probably had a bad CPU anyway (corrupt scaling/rotation), though I had hoped to fix that with a spare. Guess I'm back to square one and no longer have known-good spares. I do have another SHVC-CPU-01 that has never worked since it was given to me in the mid '90s so it's possible that it has some good parts but I can't consider anything from it "known good" and introducing parts from it will not help with troubleshooting (understatement of the century?).

Jul 7, 2017 at 10:07:21 AM
Bratwurst (79)
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Originally posted by: CZroe
Crap. Well, that SNES probably had a bad CPU anyway (corrupt scaling/rotation), though I had hoped to fix that with a spare. Guess I'm back to square one and no longer have known-good spares. I do have another SHVC-CPU-01 that has never worked since it was given to me in the mid '90s so it's possible that it has some good parts but I can't consider anything from it "known good" and introducing parts from it will not help with troubleshooting (understatement of the century?).

Just out of curiousity, what revision was this SNES? 1990, 1993, etc?

EDIT: Oh I see earlier it was a SHVC-CPU-01 too, which should make it 1990. Hm! I wonder if all the CPU/PPU isuses I've read about are common to that particular year.
 


Edited: 07/07/2017 at 10:24 AM by Bratwurst

Jul 7, 2017 at 1:27:23 PM
CZroe (31)
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Originally posted by: Bratwurst
 
Originally posted by: CZroe
Crap. Well, that SNES probably had a bad CPU anyway (corrupt scaling/rotation), though I had hoped to fix that with a spare. Guess I'm back to square one and no longer have known-good spares. I do have another SHVC-CPU-01 that has never worked since it was given to me in the mid '90s so it's possible that it has some good parts but I can't consider anything from it "known good" and introducing parts from it will not help with troubleshooting (understatement of the century?).

Just out of curiousity, what revision was this SNES? 1990, 1993, etc?

EDIT: Oh I see earlier it was a SHVC-CPU-01 too, which should make it 1990. Hm! I wonder if all the CPU/PPU isuses I've read about are common to that particular year.
 
Everything is SHVC-CPU-01 (earliest revision; has APU module for SPC700). The one from over 22 years ago has always just had a black screen. The one with corrupt scaling/rotating was a recent flea market find. The RF only one is that I'm looking at for someone else but something else is wrong with it now. I also have a SFC that is an SHVC-CPU-01 but it has served me well for 17 years and I don't want to tear into it.  


Edited: 07/07/2017 at 01:33 PM by CZroe