It is currently Thu Oct 19, 2017 6:39 pm

All times are UTC - 7 hours





Post new topic Reply to topic  [ 14 posts ] 
Author Message
 Post subject: Nintoaster White Screen
PostPosted: Mon May 15, 2017 11:36 am 
Offline

Joined: Mon May 15, 2017 11:08 am
Posts: 7
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_134440_310.jpg [ 1.86 MiB | Viewed 1347 times ]
IMG_20170515_134423_246.jpg
IMG_20170515_134423_246.jpg [ 1.88 MiB | Viewed 1347 times ]
Top
 Profile  
 
PostPosted: Mon May 15, 2017 11:39 am 
Offline

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 19104
Location: NE Indiana, USA (NTSC)
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.)


Top
 Profile  
 
PostPosted: Mon May 15, 2017 11:47 am 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
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)


Top
 Profile  
 
PostPosted: Mon May 15, 2017 12:03 pm 
Offline

Joined: Mon May 15, 2017 11:08 am
Posts: 7
I am using regular licensed nintendo carts.

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


Top
 Profile  
 
PostPosted: Mon May 15, 2017 12:26 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
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?


Top
 Profile  
 
PostPosted: Mon May 15, 2017 12:45 pm 
Offline

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


Top
 Profile  
 
PostPosted: Mon May 15, 2017 12:50 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
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.


Top
 Profile  
 
PostPosted: Mon May 15, 2017 12:58 pm 
Offline

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


Top
 Profile  
 
PostPosted: Mon May 15, 2017 1:44 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
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?


Top
 Profile  
 
PostPosted: Mon May 15, 2017 1:50 pm 
Offline

Joined: Mon May 15, 2017 11:08 am
Posts: 7
RST goes low then high, M2 goes from 7VAC to 1.5V


Top
 Profile  
 
PostPosted: Mon May 15, 2017 3:16 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
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.


Top
 Profile  
 
PostPosted: Mon May 15, 2017 3:23 pm 
Offline

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


Top
 Profile  
 
PostPosted: Mon May 15, 2017 3:30 pm 
Online

Joined: Sun Apr 13, 2008 11:12 am
Posts: 6284
Location: Seattle
Noticeably warm, but not that hot. Something could be shorted.


Top
 Profile  
 
PostPosted: Mon May 15, 2017 4:43 pm 
Offline

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


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 14 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: Gilbert, lidnariq, Yahoo [Bot] and 7 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group