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Not sure were to post this.

 

I have a SNES with the image continually flickering. The keeps going up, down, up, down like when we had an old TV with rabbit ears that was not properly adjusted. (See video)

I have already checked the power, AV cables, replaced all the capacitors, try to adjust the little screw near the oscillator crystal, replaced the oscillator crystal and I keep getting the same issue with RF, composite and component cables.

When I manage to run the test cartridge, all systems pass the test. I get no Fails.

Any ideas what to look at next?

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How many games have you tested in it?  The SD2SNES is a thirsty cart, it can have weird effects on touchy systems that may otherwise be 100% fine running legit carts.

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7 hours ago, DragonGrafx-16 said:

It might seem silly but did you try it on a different TV? 

Yes, I tried on 2 different CRT.

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7 hours ago, Tanooki said:

How many games have you tested in it?  The SD2SNES is a thirsty cart, it can have weird effects on touchy systems that may otherwise be 100% fine running legit carts.

Yes, I have a Starfox cartridge, exact same issue.

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7 hours ago, 0078265317 said:

Is it a USA SNES?  Or SFC?

Model on the board says SHVC-CPU-01. USA, I think.

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Here is a video of Starfox on another TV and the diagnostic cartridge test.

 

What I would like to know is if there is a repair manual for the SNES like they have for the Intellivision and Colcecovision that can tell you what to check, and what kind on signal to expect from a meter or oscilloscope.

 

 

IMG_20200222_131401.jpg

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Posted (edited)
29 minutes ago, dafa_123 said:

Model on the board says SHVC-CPU-01. USA, I think.

Well, does it look like this:

 

SNES-Mod1-Console-Set.jpg

 

 

or like this:

 

Wikipedia_SNES_PAL.jpg&f=1&nofb=1

 

Bonus Super Famicom. Spot the differences!

 

Nintendo-Super-Famicom-Set-FL.jpg

 

Edited by Steven Pendleton

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5 hours ago, Steven Pendleton said:

Well, does it look like this:

 

SNES-Mod1-Console-Set.jpg

 

 

or like this:

 

Wikipedia_SNES_PAL.jpg&f=1&nofb=1

 

Bonus Super Famicom. Spot the differences!

 

Nintendo-Super-Famicom-Set-FL.jpg

 

First one. US model.

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I'm wondering if it's a power issue or your chip(s) on board are failing.  Something isn't adding up.  Oh and Starfox uses the larger board FX1, it does demand a hair bit more power than a normal game but that shouldn't matter like it could with the SD2SNES.

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2 minutes ago, Tanooki said:

I'm wondering if it's a power issue or your chip(s) on board are failing.  Something isn't adding up.  Oh and Starfox uses the larger board FX1, it does demand a hair bit more power than a normal game but that shouldn't matter like it could with the SD2SNES.

Power looks good according to the meter. Which of the chips could be causing the issue? Does not look like a RAM or PPU issue from what I saw on Youtube, but I could be wrong. Since all the tests pass on the diagnostic, I am not sure what what to look at next! It seems like there is something wrong with the video output.

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I've read of rare cases of CPU failure.  If it's not the RAM or PPU maybe you have something else messed up, small cap, resistor, a rotting trace, something is up.  Also the duh moment would be swapping out a fresh ac adapter(OEM) and video cable (RF and RCA to check both ports.)

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6 minutes ago, Tanooki said:

I've read of rare cases of CPU failure.  If it's not the RAM or PPU maybe you have something else messed up, small cap, resistor, a rotting trace, something is up.  Also the duh moment would be swapping out a fresh ac adapter(OEM) and video cable (RF and RCA to check both ports.)

I have tested with a different PSU and cables. I have another SNES that works fine with the all my cables and both PSU that I have. Since I have the same issue with RF and RCA, the issues seems to be elsewhere.

 

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Posted (edited)

It looks like a sync issue too me, it's weird that you have the problem using composite. I normally see this with rgb when the sync isn't properly connected. I suspect a problem with a cap or the video chip. I think a good test would be to try RGB using Csync. if it still doesn't work most likely it would be the video\rgb chip.

Edited by Thomas83Lin
needed too

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10 hours ago, Thomas83Lin said:

It looks like a sync issue too me, it's weird that you have the problem using composite. I normally see this with rgb when the sync isn't properly connected. I suspect a problem with a cap or the video chip. I think a good test would be to try RGB using Csync. if it still doesn't work most likely it would be the video\rgb chip.

Do you know a good RGB Mod for the SNES?

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This model of SNES is notorious for failing video sync, possibly related to the BA6592F chip or other components in the video amp circuit or somewhere along the way through to the multi-out connector. An RGB cable probably will not fix the issue.

 

Test the RF-Out connection.

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Right if it's the video chip, rgb will not fix\bypass the problem. but it would be a good test on the chance its something in between.

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4 hours ago, Bratwurst said:

This model of SNES is notorious for failing video sync, possibly related to the BA6592F chip or other components in the video amp circuit or somewhere along the way through to the multi-out connector. An RGB cable probably will not fix the issue.

 

Test the RF-Out connection.

I have the same issue with RF.

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I checked all the lines for the PPUs and RAM and everything looks fine. I also checked the grounds and VCC and they also llook fine. When I look at the electric diagram, I see pin 100 of PPU2 U3 that says CSYNC that goes to both the RF Module and the AV out connector. Does anyone know if that is what is used to sync the image on the TV? If U3 is not sending the correct signal out of pin 100, could that be the issue?

 

Thanks.

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On 4/8/2020 at 8:02 AM, Bratwurst said:

This model of SNES is notorious for failing video sync, possibly related to the BA6592F chip or other components in the video amp circuit or somewhere along the way through to the multi-out connector. An RGB cable probably will not fix the issue.

 

Test the RF-Out connection.

Do you know if pin 100 of U3 is the one doing the video sync?

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Looks like it. Check any components that run between U3 and the RF-Out and Multi-Out. If it's the PPU2 itself you're kind of out of luck and will have to source a donor board to rob the chip from, fairly involved surface mount desoldering/soldering. Would probably be easier and cheaper to source another working SNES at this point in time.

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If I check with an oscilloscope, what kind of signal should I be getting out of pin 100? If I had a reference, I could compare.

 

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