Hi All,
Was really hoping I could crack this one but hitting a dead end. With some help here a few years back I got my opentendo build up and running, more or less. Finally getting around to try and finish it up, but I seem to have gone backwards.
The initial problems I had seemed around getting an OK clock signal going, which with some variation in parts the board fired up at least.
Coming back to the project now, I had no luck at power on, but I saw the spec of a resistor and capacitor around that area changed, so I thought right lets get back on spec.
After alot of fiddling, I have what I think is a good clock signal, and what I think might be OK on M2 and CPUCLK. RST is also staying high.
From the clock crystal itself:Then from M2 on the CPU:And CPUCLK:RST staying high:I'm not sure, if M2 should look like that, or perhaps the problem is already there.
But assuming that's OK, I was then wondering if its something with the CIC workaround. The "How to fix a NES mainboard without 10NES lockout chip?" had alot of info on this, so I thought I'd switch from redherrings NullCIC which I had before, to the design on there (as running out of ideas really..)
Looking at the 1Mohm resistor going to 74HCU04, I get this at power on:I thought that might repeat when I touch RST to ground, but it doesnt seem to, I don't know if that's related. The screen output does glitch to black and then back to this white after doing that though.
Here's current state of the board:And output:And that's where I'm a bit stuck. I've got various spare parts if maybe I've fried something along the way.. only thing I don't have is any other game cartridge.
Any thoughts on where the problem might lie / other bits to test would be much appreciated!!
Was really hoping I could crack this one but hitting a dead end. With some help here a few years back I got my opentendo build up and running, more or less. Finally getting around to try and finish it up, but I seem to have gone backwards.
The initial problems I had seemed around getting an OK clock signal going, which with some variation in parts the board fired up at least.
Coming back to the project now, I had no luck at power on, but I saw the spec of a resistor and capacitor around that area changed, so I thought right lets get back on spec.
After alot of fiddling, I have what I think is a good clock signal, and what I think might be OK on M2 and CPUCLK. RST is also staying high.
From the clock crystal itself:
But assuming that's OK, I was then wondering if its something with the CIC workaround. The "How to fix a NES mainboard without 10NES lockout chip?" had alot of info on this, so I thought I'd switch from redherrings NullCIC which I had before, to the design on there (as running out of ideas really..)
Looking at the 1Mohm resistor going to 74HCU04, I get this at power on:
Here's current state of the board:
Any thoughts on where the problem might lie / other bits to test would be much appreciated!!
Statistics: Posted by vinnieb — Mon Feb 03, 2025 4:45 am — Replies 1 — Views 108