Nintoaster White Screen

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

Moderators: B00daW, Moderators

Post Reply
CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 11:36 am

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?
Attachments
IMG_20170515_134440_310.jpg
IMG_20170515_134423_246.jpg

tepples
Posts: 21708
Joined: Sun Sep 19, 2004 11:12 pm
Location: NE Indiana, USA (NTSC)
Contact:

Re: Nintoaster White Screen

Post by tepples » Mon May 15, 2017 11:39 am

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.
Tengen or Nintendo?

(If it's jargon among console repair technicians and modders, I'm not sure to what you're referring.)

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 11:47 am

CoatHanger wrote:All of the cartridge connections are reading as connected with nothing shorted out and the led is not blinking.
Does the reset button work?

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)

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 12:03 pm

I am using regular licensed nintendo carts.

The reset button does work. The only real diagnostic tools I have available are a multimeter.

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 12:26 pm

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?

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 12:45 pm

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.

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 12:50 pm

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.

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 12:58 pm

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.

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 1:44 pm

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?

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 1:50 pm

RST goes low then high, M2 goes from 7VAC to 1.5V

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 3:16 pm

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.

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 3:23 pm

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.

lidnariq
Posts: 8692
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nintoaster White Screen

Post by lidnariq » Mon May 15, 2017 3:30 pm

Noticeably warm, but not that hot. Something could be shorted.

CoatHanger
Posts: 7
Joined: Mon May 15, 2017 11:08 am

Re: Nintoaster White Screen

Post by CoatHanger » Mon May 15, 2017 4:43 pm

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.

Post Reply