NESRGB fail toploader

[that1crzywhtguy]

Hi everyone, and thanks in advance for any support and help with this one—I think I'm out of ideas.

This is my second NESRGB install, and first in a toploader.

I desoldered the PPU using my new s-993a desoldering gun (btw, do not recommend, it's already failed and I'm in return process with Amazon). This didn't go very smoothly, and there were some traces damaged. I repaired these with wires and tested for continuity and short circuits.

I was not surprised when I finally got it all installed that it wasn't functioning. I assumed I'd fried the PPU, so to check I tore down my old NESRGB frontloader and inserted the toploader's PPU and it fired right up... So, I could see the PPU wasn't the problem.

I inserted the other functioning PPU from the frontloader into the toploader and still nothing. Next I got the schematic out and buzzed all connections on the PPU to where they are supposed to end up. All 40 pins, solid connections and no shorts.

So, I inserted the PPU directly and tried to get a signal from the RF. When powered on, the screen turns black (brighter then fading dark). This is clearly not right.

If the PPU is good, and all connections are sound, what's next? I would imagine maybe bad CPU, but I never got near it upon desoldering the PPU, so I can't imagine it got hot at all. Bad ram? Same as with CPU, not sure what would cause damage?

Do I need better than my multimeter to diagnose this one?

Hoping I don't need to sink dollars into another toploader.

Thanks again in advance.

[DirkSwizzler]

I’m still pretty novice at diagnosing things that didn’t go to plan. But here’s a couple things I would try:

Make sure you’re grounded. Turn on the Nintendo for a minute or two and feel around the board for any chips that are significantly hot. ESD is a thing and I’ve heard NES units are especially susceptible.

Test connections between the ppu pins while inserted and the underside of your socket. It’s always possible the socket itself is the problem.

Maybe reflow your soldering? My gcdual install showed all the proper continuity when I was pressing on points with my probes. But was failing to run until I reflowed all the soldering points twice.

[that1crzywhtguy]

Thanks for the reply. As I mentioned, I got the schematic out and buzzed all connections on the PPU to where they are supposed to end up. All 40 pins, solid connections and no shorts. In other words, I went well passed the socket and into the destination of each signal.

Ground is solidly connected where it should be, and nothing seems to be getting hot.

[DirkSwizzler]

As I mentioned, I got the schematic out and buzzed all connections on the PPU to where they are supposed to end up.

K, it wasn’t really clear whether you checked from your solder points to the destination or directly touching the chip on the topside.

Ground is solidly connected where it should be

By “where it should be” I hope you’re referring to your wrist strap. To be absolutely clear I’m saying that *you* need to be grounded while touching a PCB

[that1crzywhtguy]

I see. I don't use wrist strap, but discharge when working with electronics and work on laminate.

[that1crzywhtguy]

What I was really hoping for was a way to diagnose the problem now, hopefully without a scope (I don't own one).

[that1crzywhtguy]

Bit of an update... I replaced the cpu for one that was known working, and its still not functioning, same as before...

Do I try swapping ram chips next?

[thebigcheese]

You said you verified all the connections are good, but are you certain that they are all correct? With the NESRGB plugged in (but the console off), make sure that pin 1 of the socket for the PPU on the NES connects to pin 1 of the PPU on the NESRGB and so on. It's possible you put the adapter plate on backward and thus have all the pins going to the wrong place. If you've got any pictures you can post, that might also be helpful.