Nintoaster White Screen
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Nintoaster White Screen
I recently started to work on my Nintoaster project that I started years ago. I removed the old 72 pin connector and soldered on a game genie connector in it's place. I replaced the RF modulator with the composite Video Amp Circuit. The NES would only display a white screen. One of the capacitors was bulging (1uf), so I replaced it, which gave me a the Tetris Title Screen. This morning I went to check on the board and it was giving me a white screen again, so I replaced a different capacitor (100uf) along with the original (1uf), but nothing changed. All of the cartridge connections are reading as connected with nothing shorted out and the led is not blinking. The pins on the game genie connector were also cleaned and verified to be making contact. Other than replacing the third capacitor (2.2uf), I cannot think of anything else to do. Any ideas?
Re: Nintoaster White Screen
Tengen or Nintendo?CoatHanger wrote:The NES would only display a white screen. One of the capacitors was bulging (1uf), so I replaced it, which gave me a the Tetris Title Screen.
(If it's jargon among console repair technicians and modders, I'm not sure to what you're referring.)
Re: Nintoaster White Screen
Does the reset button work?CoatHanger wrote:All of the cartridge connections are reading as connected with nothing shorted out and the led is not blinking.
Solid white screen implies PPU is still generating signal at 21MHz crystal is still generating clock, but the CPU is for some reason never or stopping executing code.
What diagnostic tools do you have access to? (logic analyzer, oscilloscope, multimeter, flashcart, &c)
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Re: Nintoaster White Screen
I am using regular licensed nintendo carts.
The reset button does work. The only real diagnostic tools I have available are a multimeter.
The reset button does work. The only real diagnostic tools I have available are a multimeter.
Re: Nintoaster White Screen
Using the multimeter, check the address and data lines from the CPU. Are any changing? If not, what are the contents of address and data bus resting at? And with which game?
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Re: Nintoaster White Screen
I am using the nintendo version of tetris. My multimeter lacks a frequency counter, so I'm not really sure if it will help in probing the cpu.
Re: Nintoaster White Screen
Don't care about frequency. Just whether you see 0V, ≈4V, or something in-between on each pin. The objective is figuring out whether the CPU has crashed or is in an infinite loop, and if it has crashed what was the last address/data it saw.
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Re: Nintoaster White Screen
Everything is between 0-4V, with all of the data lines being about 0-.5v, and the address lines ranging from 0v (up to A06), then to 3.8v (A07-A08), then to 1.2V, then to 2.85v, then to 3.8v, and finally ~0 on A15.
Re: Nintoaster White Screen
Well, not an infinite loop. Hard to say whether the CPU ever actually executed anything but with that particular address it seems less likely.
CPU /RST is low while the button is pressed and goes high afterwards?
Does your multimeter have the ability to measure AC volts? If so, does M2 go from ≈0VAC when /RST is low to >1VAC when /RST is high?
CPU /RST is low while the button is pressed and goes high afterwards?
Does your multimeter have the ability to measure AC volts? If so, does M2 go from ≈0VAC when /RST is low to >1VAC when /RST is high?
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Re: Nintoaster White Screen
RST goes low then high, M2 goes from 7VAC to 1.5V
Re: Nintoaster White Screen
Unfortunately, everything that I can think of to test without access to better tools looks ok. The only "easy" guess I have remaining is that one of the solder joints or wires are loose or partially broken such that whether it's connected depends on the exact angle everything's at. :/
This is classically a situation in which one would use a logic analyzer to determine whether the CPU is executing the correct things.
This is classically a situation in which one would use a logic analyzer to determine whether the CPU is executing the correct things.
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Re: Nintoaster White Screen
I'll have to check over all the connections again I suppose. How hot is the CPU supposed to get? Touching it with my thumb, it's hot enough to feel very uncomfortable.
Re: Nintoaster White Screen
Noticeably warm, but not that hot. Something could be shorted.
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Re: Nintoaster White Screen
Must have been the game genie connector I was using. I pulled out a second cartridge connector I had and it worked after I wired it up. If there was a problem with my soldering job the first time around, it was not immediately apparent.