Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Discuss technical or other issues relating to programming the Nintendo Entertainment System, Famicom, or compatible systems.

Moderator: Moderators

lidnariq
Posts: 10548
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by lidnariq » Fri Mar 19, 2021 2:08 pm

Liengamer wrote:
Fri Mar 19, 2021 2:02 pm
Ok so I´ve measure them all with my scope. First thing that is kinda suspect to me is the fact that on all of the from low to high "inverted" pins I´m only getting 3.9V and not 5V like on Vcc on the inverter.
It's not too concerning; most of the electronics from the time can't emit voltages above 4V despite being powered by 5V anyway.

It is a little bit lower than the HCU04 should be capable of emitting when powered at 5V - the datasheet says under load you should see 0.2V-0.5V below the voltage supply, not a whole volt, but ... 4V should still work correctly.

edit: that said, make sure things change in response to pressing the button.
The second weird thing is the fact that im getting no voltage what so ever on inverter 5 (pins 10/11) is that normal or is something broken there?
10+11 are the audio amplifier, so the middling voltages and unchanging output is expected (unless sound is playing). The other 5 inverters are used digitally.

Liengamer
Posts: 34
Joined: Wed Mar 03, 2021 8:04 am
Location: Germany

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by Liengamer » Fri Mar 19, 2021 2:17 pm

Ok so on when the reset button is getting pressed pin 1 is low and pin 2/3 are high, pin 8 is low and pin 9 is high

Liengamer
Posts: 34
Joined: Wed Mar 03, 2021 8:04 am
Location: Germany

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by Liengamer » Fri Mar 19, 2021 2:19 pm

I´ve just notice that the 2 wire mod was not fully connected but after reconnecting it the "sometimes not working led problem" didnt happen again. Now I´m just left with the absolutly corrupted garbled and black and white video

lidnariq
Posts: 10548
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by lidnariq » Fri Mar 19, 2021 2:43 pm

Ok, cool, so the reset button now works correctly?

Garbled video - is it stable? by which I mean, does it draw the same nonsense consistently, or it is shaky?

For black-and-white video - this is a PAL nes, on a PAL TV, so check for 26.6017125MHz on CPU pin 29 and PPU pin 18. It should be within 1% (or better? I don't know) for your TV to accept that it's a valid color signal.

Liengamer
Posts: 34
Joined: Wed Mar 03, 2021 8:04 am
Location: Germany

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by Liengamer » Fri Mar 19, 2021 2:49 pm

lidnariq wrote:
Fri Mar 19, 2021 2:43 pm
Ok, cool, so the reset button now works correctly?

Garbled video - is it stable? by which I mean, does it draw the same nonsense consistently, or it is shaky?

For black-and-white video - this is a PAL nes, on a PAL TV, so check for 26.6017125MHz on CPU pin 29 and PPU pin 18. It should be within 1% (or better? I don't know) for your TV to accept that it's a valid color signal.
Yeah the power button now works perfectly fine. No the video is definitly anything else than what could be caled stable it is really shaky and has something like "corrupted characters" I´m using super mario bros 3 wich normally works perfectly fine. Also I´m getting a perfect 26.60mhz sinewave on both of the clock pins

lidnariq
Posts: 10548
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by lidnariq » Fri Mar 19, 2021 2:59 pm

Ok, I think there's something wrong with the analog video path out of the PPU. Do you know what baseband video looks like? ( https://commons.wikimedia.org/wiki/File ... al_PS1.png )

I'd follow the signal from pin 21 of the PPU, trying to synchronize on those bottom pulses (which are hsync), going via Q1 (2SA937), the ferrite bead FC2, before entering the RF modulator.

Liengamer
Posts: 34
Joined: Wed Mar 03, 2021 8:04 am
Location: Germany

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by Liengamer » Fri Mar 19, 2021 3:09 pm

lidnariq wrote:
Fri Mar 19, 2021 2:59 pm
Ok, I think there's something wrong with the analog video path out of the PPU. Do you know what baseband video looks like? ( https://commons.wikimedia.org/wiki/File ... al_PS1.png )

I'd follow the signal from pin 21 of the PPU, trying to synchronize on those bottom pulses (which are hsync), going via Q1 (2SA937), the ferrite bead FC2, before entering the RF modulator.
The weird thing about this is the fact that when i try to launch super mario there is this "corruption" with the characters going on but after something like a seacond the video just turns black but I can sometimes see some really quick flashes. But I will definetly follow the traces from pin 21

Liengamer
Posts: 34
Joined: Wed Mar 03, 2021 8:04 am
Location: Germany

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by Liengamer » Fri Mar 19, 2021 3:15 pm

lidnariq wrote:
Fri Mar 19, 2021 2:59 pm
Ok, I think there's something wrong with the analog video path out of the PPU. Do you know what baseband video looks like? ( https://commons.wikimedia.org/wiki/File ... al_PS1.png )

I'd follow the signal from pin 21 of the PPU, trying to synchronize on those bottom pulses (which are hsync), going via Q1 (2SA937), the ferrite bead FC2, before entering the RF modulator.
The video signal from the ppu looks similar but doesn´t contain the part where the brightness data would be stored in, this part is just constantly high

lidnariq
Posts: 10548
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Nes Power Led flashes realy fast+getting only 2,3Vavg on 5V rail

Post by lidnariq » Fri Mar 19, 2021 3:17 pm

On a PAL NES, about 1/4 of the time is just displaying black; you may need to keep looking for a bit. (Only 239 out of 312 scanlines contain picture; the other 70 and 3 contain black or vsync)

If your scope has a VIDEO sync option that'll help, but you may not

Post Reply