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PostPosted: Mon May 25, 2015 8:55 pm 
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I've been working on a 3D-printed multi-out panel for the toploader and it was working great right up until I tried closing the case back up, at which point the video output stopped working on either of the two video outputs I had wired up (composite and component), and the only output of any kind that I get is a slight audio hum. The screen is just black, not even a momentary blip as I throw the power switch like I would normally see, even with no cart inserted. The power supply and main power rail are fine, but that's as far as I've gotten with my troubleshooting at this point. Any ideas?


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PostPosted: Tue May 26, 2015 7:35 am 
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Try removing your component video encoder modifications, and un-do everything other than leaving the NESRGB in place. Be sure power is going where it's needed.

From my experiences I've found the second 7805 for the NESRGB isn't really necessary. Try removing it if you are using it just to eliminate a node of failure.


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PostPosted: Tue May 26, 2015 10:29 am 
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Alright, I'll give that a shot. I wasn't using the extra regulator, I was planning on metering out the main regulator to check total current consumption after the mod was complete and decide at that point whether or not it was necessary, or maybe just replace/upgrade the main regulator instead.


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PostPosted: Tue May 26, 2015 11:06 am 
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No luck. I even tried removing the NESRGB completely and putting the PPU back in and wiring up the composite video directly, and I get absolutely nothing out. No picture, no sound. Did I get the wiring right? Yes, I know the red wire isn't needed. (R: +5V, Y: Video, W: Audio, B: Gnd)

Image


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PostPosted: Wed May 27, 2015 9:04 am 
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You can figure out if the CPU is alive by probing the address lines with your audio input. If you hear a bunch of funky square waves, then the address lines are pulsing, which means it's at least doing something.


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PostPosted: Wed May 27, 2015 6:02 pm 
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Started poking around with my multimeter on Hz/duty cycle to see what, if anything, I could find. No signals on the CPU and then it got hot enough I could smell it. So... that sucks. I read 350ohm between +5v and Gnd on the CPU, and about 2.5kohm between +5v and Gnd on the PPU (removed from the console). Something definitely went boom.


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PostPosted: Wed May 27, 2015 7:06 pm 
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Just removed the CPU, and by itself, resistance from +5V to Gnd is 650ohm. The main board, with CPU and PPU removed, shows 850ohm from +5V to Gnd. Is that normal, or is something else on the board blown?


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PostPosted: Wed May 27, 2015 7:23 pm 
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Location: Seattle
On a known-functioning NES-CPU-07 board, with the power switch daughterboard removed, CIC removed, but the CPU and PPU present, I see 260Ω from Vcc to Gnd, and 250Ω from Gnd to Vcc.

The CPU, not in a socket, reads 660Ω from Vcc to Gnd. The above mainboard without the CPU measure 427Ω. I damaged one of the pins on the PPU when I socketed my NES, so forgive me for not measuring that part...


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PostPosted: Wed May 27, 2015 8:34 pm 
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Hey I've troubleshooted my nes-101 a few times. Do you have any spare parts? To begin with I'd probably verify power. Check for anything that looks blown on the board. After I'd try and take out the nesrgb and put coax back or a simple av mod. PM me and I can try and help you out as much as I could.


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PostPosted: Wed May 27, 2015 11:54 pm 
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Icelvlan wrote:
Hey I've troubleshooted my nes-101 a few times. Do you have any spare parts? To begin with I'd probably verify power. Check for anything that looks blown on the board. After I'd try and take out the nesrgb and put coax back or a simple av mod. PM me and I can try and help you out as much as I could.


NESRGB is out, PPU is back in place, that's the way it was when the CPU temp shot up. I don't currently have any spare parts, but I'm ordering a couple of beat-up-but-functional toasters for parts. I'm also going to order new caps and a new 7805, to start. I probably need to replace them regardless, and then I can rule out the power circuit.


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PostPosted: Wed Jun 03, 2015 9:41 am 
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Well, I replaced the regulator and all of the electrolytic capacitors, but when I press-fit the CPU back in place (didn't want to solder it back in just yet because I wanted to test the CPU on another working board first), it heated up again to the point of almost burning my fingers. I had another CPU taken out of another console, so I tried press-fitting that one in, and it didn't heat up at all. My PPU doesn't heat up either, so it might just be a fried CPU. At this point, desoldering the CPU is enough of a pain that I don't want to solder in a new one until I've tested it, so I'm buying a working front-loader that I plan to pull the CPU/PPU out of and socket them both so I can use it as a test board. I was really glad to learn that the 'G' revision CPU/PPU are so common. I was worried it might be a top-loader specific revision. Just gonna take it one step at a time. I can rebuild it. I have the technology!


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PostPosted: Wed Jun 03, 2015 1:54 pm 
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In general if an IC heats up instantly like that, it's safe to guess it might be toast. If you aren't pressing it into a socket, though, that's not a real test. It's hard to guarantee the needed pins are all making contact. Just solder in a socket!


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PostPosted: Wed Jun 03, 2015 3:47 pm 
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Yes, I know it's not a real test, but I don't really want a CPU socket in my top-loader. I was more interested in testing the fact that with the CPU out, nothing else gets hot and the power rail seems stable. Then, the minute I press the CPU into place it (and only it) rapidly heats up to the point of burning. Once I get my hands on a working front-loader I'll put sockets in that and use it as a test board, and if the CPU does turn out to be bad, I'll just use the CPU from that front-loader.


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PostPosted: Sat Jun 06, 2015 1:18 pm 
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qwertymodo wrote:
Yes, I know it's not a real test, but I don't really want a CPU socket in my top-loader.

I highly suggest you do so, that way if the CPU somehow dies again it'll save you a ton of time replacing it.


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PostPosted: Tue Jun 09, 2015 1:03 pm 
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There are serious clearance issues with the NESRGB adapter board. As in, basically the entire row of CPU pins is within ~0.1mm of the PPU signal pins on the adapter board. Unless I can find a seriously low-profile socket, it's just not going to happen. I'm ordering a few samples of the Samtec SL-series low-profile machine screw strips, but even then I'm not sure how much clearance I'll have.


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