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NES toploader, loud audio buzz and garbled screen.

NES Repair

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#1 boogieman! OFFLINE  

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Posted Sun Nov 26, 2017 5:22 PM

I have a strange one... I have a toploader NES.  I plug in the power and RF line and turn the console on.  I get a very loud audio buzz and the video is basically moving horizontal stripes on the screen with no inkling of being actual graphics.

 

Does anyone have an idea of what this could be or how to go about diagnosing this?



#2 Tanooki OFFLINE  

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Posted Sun Nov 26, 2017 7:04 PM

Sounds like you might have a bad RF module there or the plug in the back of the system it feeds into.  I recall decades ago seeing(hearing) that same problem with what I thought was a crapped out Fairchild F2 system but it was a wasted cable, not the system.



#3 mbd30 OFFLINE  

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Posted Sun Nov 26, 2017 7:45 PM

Another simple possibility is bad AC adapter.



#4 boogieman! OFFLINE  

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Posted Sun Nov 26, 2017 7:57 PM

Another simple possibility is bad AC adapter.

Tried the AC adapter on a working model 1 nes and it worked (the model 1, not the faulty one).  Just to make sure, I tried another AC adapter and same symptoms.  

 

Is there an easy way to test an RF Module?  The only diagnostic tool I have is a digital multimeter.

 

Just FYI I do have a solder station and am comfortable working on this stuff.  I figured I'd mention it just in case it helps.

 

EDIT: I tried the RF cord that attaches to the TV, it's ok on other systems.


Edited by boogieman!, Sun Nov 26, 2017 8:15 PM.


#5 CatPix OFFLINE  

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Posted Sun Nov 26, 2017 9:29 PM

It's you're OK with a soldering cable, try to wire out video and audio from the board. At least the video.
 
hvc-101_video.gif
 
If you do'nt have those parts, you can still try to directly wire the PPU pin 21 to a monitor and see if you get even a faint, but useable picture.
If you get a clear picture, then you found out that your RF block is busted. If you still get a bad image, then the problem is from the NES itself.


#6 boogieman! OFFLINE  

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Posted Sun Nov 26, 2017 10:20 PM

 

It's you're OK with a soldering cable, try to wire out video and audio from the board. At least the video.
 
 
 
If you do'nt have those parts, you can still try to directly wire the PPU pin 21 to a monitor and see if you get even a faint, but useable picture.
If you get a clear picture, then you found out that your RF block is busted. If you still get a bad image, then the problem is from the NES itself.

 

 

OK, this sounds doable.  I'll give this a try tomorrow after work, I'll have to look if I have parts, if not, I'll try the pin 21 like you mentioned.  Thanks, I really appreciate the help!



#7 SignGuy81 OFFLINE  

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Posted Sun Nov 26, 2017 10:29 PM

I found this video it may be similar to your problem.  He mentions audio buzz but I think it is black screen instead of stripes on this unit.  This unit had both a bad CPU and PPU.  He tested the CPU in a known good board and it was bad.  First the bad CPU was replaced and then it still had the audio buzz and still black screen.  After replacing the PPU as well then the unit was working.

 

Anyway here is the video.

 

https://www.youtube....h?v=flruCOCFDS4



#8 0078265317 OFFLINE  

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Posted Sun Nov 26, 2017 11:28 PM

I found this video it may be similar to your problem.  He mentions audio buzz but I think it is black screen instead of stripes on this unit.  This unit had both a bad CPU and PPU.  He tested the CPU in a known good board and it was bad.  First the bad CPU was replaced and then it still had the audio buzz and still black screen.  After replacing the PPU as well then the unit was working.

 

Anyway here is the video.

 

https://www.youtube....h?v=flruCOCFDS4

 

Interesting video



#9 boogieman! OFFLINE  

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Posted Mon Nov 27, 2017 3:37 PM

OK, I have some additional info.  I didn't have the components to make the circuit, but there is absolutely nothing on pin 21 of the ppu as far as video signal goes.  I also checked the voltage regulator, and I get around 11 volts, 0 (ground) and around 5.  So voltage is good, at least there.

 

I actually watched those youtube videos yesterday before I jumped on here.  I am under the impression I have a bad PPU or CPU or both.

 

I have a spare parts nes that has other issues cosmetically (broken case and bad 72 pin connector), but has good components.  Unless you guys have different ideas, my next step will be to try to transplant those into this system.  I eventually wanted to do an nesrgb/svideo mod to this system with the snes style multiout, so the plan for now is to order sockets, solder those to the board, and see if the replacement chips fix the unit.  I will need to socket the ppu holes anyway to do the rgb mod, so I won't be out a whole lot in the meantime.  It may be awhile since I have to order the parts, but I'll keep you guys updated.



#10 NinjaWarrior OFFLINE  

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Posted Mon Nov 27, 2017 10:35 PM

If the RF doesn't solve it

 

Replace the PPU



#11 mobiusstriptech OFFLINE  

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Posted Mon Dec 4, 2017 8:05 PM

Frequently if you have a bad PPU the chip itself will get hot while powered on. I wouldn't assume the PPU is dead just because you didn't get video from pin 21. You were still taking a signal that wasn't properly attenuated and trying to use it. Based on the fact that you were getting scrolling lines and some picture I would start with that RF modulator. They are very commonly broken plus the toploader had bad rf to begin with. If the PPU is not getting hot, then just try the NESRGB mod. If you still have issues, then it will be easy enough to swap the PPU.





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