Help fix a NES Clone (Phantom System)

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lidnariq
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Re: Help fix a NES Clone (Phantom System)

Post by lidnariq » Sat Feb 18, 2017 4:55 pm

Instead of cutting the trace here, they could instead have removed R2.

(That's my best guess as to the described difference)

In the other picture I still have no idea what's going on with the CIC, but this picture clearly shows reconnecting CIC /RESET OUT to the CPU's and PPU's /reset input.

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Fisher
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Re: Help fix a NES Clone (Phantom System)

Post by Fisher » Sat Feb 18, 2017 4:59 pm

This makes me even more confused... :oops:
Does the yellow wire really connects to PPU /RESET??

As stated before, this makes no sense... :roll:

lidnariq
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Re: Help fix a NES Clone (Phantom System)

Post by lidnariq » Sat Feb 18, 2017 5:09 pm

Maybe orange doesn't connect to PPU /IRQ ???? Maybe orange instead connects to CIC /RESET OUT ?

This would ensure that the color modulator booted up in a fixed phase relative to the PPU.

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tokumaru
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Re: Help fix a NES Clone (Phantom System)

Post by tokumaru » Sat Feb 18, 2017 5:42 pm

Fuck, does the NES have a lot of screws! Here's where the wires go:
pal-m-nes-01.jpg
pal-m-nes-02.jpg
pal-m-nes-03.jpg
Forgot to take a picture of the other side of the main board... hope you don't need it, 'cause I already put the NES back together! :mrgreen:

Anyway, the only cut trace I can see is the one by the yellow wire.

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Fisher
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Re: Help fix a NES Clone (Phantom System)

Post by Fisher » Sat Feb 18, 2017 5:48 pm

@lidnariq:
Yes, this makes a lot more sense!
It would potentially sync the PPU and the transcoder.
Bad colors could be related to something around these wires, interference maybe? (Likely not, but...)

I'll take a closer look at the pictures I've posted before to try to confirm that.
Maybe Tokumaru can also confirm the orange wire when he looks at it?

@l_oliveira:
Maybe Zepper would like your help too.
Looks like the guy that was fixing his console had not get good news yet.
I have no idea of where he lives...
I don't offer my help because I'm not yet confident enough to try to fix other people's stuff, only my old crap. So if it dies, it's dead (I still didn't understand how the heck I've fried a 9112, an MMC3 clone. Shouldn't it accept a high level on any of his pins, except GND? ).
I think I'm still a very unexperient rookie, with tons of stuff to learn and lots of information to "digest".

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tokumaru
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Re: Help fix a NES Clone (Phantom System)

Post by tokumaru » Sat Feb 18, 2017 5:59 pm

Orange appears to be PPU /RST... and yellow to the CIC... Is this correct?

lidnariq
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Re: Help fix a NES Clone (Phantom System)

Post by lidnariq » Sat Feb 18, 2017 6:06 pm

Ok, somehow I got orange and yellow backwards. How did I do that?

Yellow is CIC /RESET OUT, and orange is the buffered and synchronized copy of it that's forwarded to the mainboard for CPU /RESET and PPU /RESET.

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tokumaru
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Re: Help fix a NES Clone (Phantom System)

Post by tokumaru » Sat Feb 18, 2017 6:12 pm

Does that make the work of the transcoder board any easier to understand?

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Fisher
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Re: Help fix a NES Clone (Phantom System)

Post by Fisher » Sat Feb 18, 2017 6:13 pm

Great!
More one mistery solved!
Thanks again!
So these 2 wires are used to sync the PPU and the transcoder, just as Lidnariq said!
What could cause the bad colors?
Something related to these signals?

Edit:
Again I was trying to type on the cell phone and got a answer just before posting...
@lidnariq: I think that was my mistake... oops :-(
@tokumaru: yes, it makes sense now!

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l_oliveira
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Re: Help fix a NES Clone (Phantom System)

Post by l_oliveira » Sat Feb 18, 2017 6:57 pm

Probably the transcoder board needs to control reset so it knows when reset is being held low so it doesn't run without video signal coming from the PPU. That would result on weird wavy patterns showing on the screen, I believe.

I believe that bad colors are due to different color encoding used on PAL(YUV) vs NTSC(YIQ). They convert the phase but the signal is still in YIQ as originally generated by the PPU.

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Re: Help fix a NES Clone (Phantom System)

Post by tepples » Sat Feb 18, 2017 8:18 pm

YUV and YIQ are essentially the same color space, just with the chroma plane rotated by 33 degrees. Use of YIQ with NTSC theoretically allows for more luma detail without color fringing because the Q axis is narrower in bandwidth, but few TVs support it, most instead decoding NTSC as YUV.

The PPU's output isn't generated with the ordinary QAM (quadrature amplitude modulation) method associated with YUV or YIQ. It's actually 12PSK (phase shift keying) as a shortcut for generating a signal that a YUV or YIQ decoder can still handle.

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tokumaru
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Re: Help fix a NES Clone (Phantom System)

Post by tokumaru » Sun Feb 19, 2017 1:15 am

Oops, missed this post.
l_oliveira wrote:If you ever come by Brasilia area let me know I am sure I can revive your nes. I'd wager you broke a trace on the oscillator circuit and it's no longer oscillating. No clock, no video.
Thanks. The original crystal had something like a wire around it, soldered to its metal body... I have no idea what the hell that was. One day I'll look into fixing that NES, thanks again for offering to help.
Btw, the Polivox Atari with "proper green board" is simple a REV 16 4 switches USA board. It was not made in Brazil hence why they had that transcoder board inside the ICs cage stuck inside with a sponge on the bottom so it would not rattle. ;)
Yeah, it was glued to the top of the CPU and TIA, I think. Very sticky, there's still a bunch of sponge pieces on that board I photographed, and on the chips.

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l_oliveira
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Re: Help fix a NES Clone (Phantom System)

Post by l_oliveira » Sun Feb 19, 2017 6:36 am

The sponge foam degrades with time. Becomes a pulp after some 20 years or so. The REV16 board is from 1981 and they were sold here around 1984 so they likely had the boards installed in 1983. Plenty of time for the foam to degrade and turn into a sticky, yucky pulp.

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Fisher
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Re: Help fix a NES Clone (Phantom System)

Post by Fisher » Sat Feb 25, 2017 8:10 am

Great!!
I'll try to use the carnival's holyday to rebuild/fix the board an do some tests.

I just love this holyday!!
I spend most of the time sleeping and playing with my kids and stuff!! :lol: :lol: :lol:

melovictor
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Re: Help fix a NES Clone (Phantom System)

Post by melovictor » Sat May 06, 2017 2:22 pm

Hi all,

So if I am to convert my original Phantom System from PAL-M to NTSC all I have to do is to put a NTSC NES crystal in it, nothing more?

Thanks,
Victor
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