So over the past year, I've had a side project to convert my NES to NTSC and RGB mod it. RGB modded it no problem, and just recently I got hold of the required parts to convert it to NTSC (CPU/PPU/crystal) So I installed the new parts, and now when I power it up, I get absolute nothing. As if the console is completely dead. Not even flicker on the screen when switching it on. Just totally dead. The only thing I get is the red power light, and a brief flash of red or blue on the screen when I unplug the video cable. Tried multiple scart cables - nothing. Tried csync and composite video - nothing. Tried putting the old CPU/PPU back in - nothing. The entire console seems dead... Any ideas what I could check?
Symptoms and description hint at the quartz crystal not oscillating. There may be a different crystal driver circuit in PAL vs NTSC machines as this stuff often goes undocumented. With a scope you could tell this immediately. Without scope, you need to come up with a way to make a clock presence visible somehow. You could use any clock pin on any IC, except for maybe the CIC, dunno.
EDIT: Check composite output first. See if you get anything from that. Changing the crystal from a Pal one to a ntsc one works without issue(so long as cpu and ppu are changed too). I doubt the crystal is the issue. I would recheck your work on the rgb mod. My first thought though is the sockets for the cpu and/or ppu. They can be hit or miss in my experience. So check continuity between the pin on the ppu/cpu and the pin on the soldered side of the socket . Also check your 7805 for 5v, to make sure it's not that. If everything checks out, I suggest removing rgb mod and running the NES with NTSC parts installed directly to see if it works like that. If not, restore console to pal and test. If it works, redo rgb mod, test, if works, redo ntsc . Good luck
Ok I figured it out. Both the donor CPU and PPU are bad. I did however discover that the SCART cable I was using has a resistor on the sync line built into the console end (bought from retrogamingcables.co.uk) and while it worked when the console was PAL, it no longer works when it's NTSC. Switched to my Gamecube's SCART cable and I was able to confirm that the console works fine with the old CPU and PPU, but with the NTSC CPU, I get nothing at all. With the NTSC PPU, it does boot, but the graphics are all scrambled. Wiggling the cart and resetting just shows the exact same corruption every time, so I think that's pretty evident of a bad PPU. Oh well, the Donor CPU and PPU were from an "untested" famicom I got on ebay for £13. Can't complain really. Back to the drawing board then.
