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PostPosted: Mon Sep 26, 2005 7:26 pm 
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I have an extra top loader that I don't mind experimenting with to try and figure out how to get perfect video out of it.

Here's what I know so far:

- the top loader / front loader have the same CPU and exact same PPU
- the video quality does not improve with the AV mod

The only thing I did notice between the top loader and front loader is the actual traces on the board. The top loader uses very thin traces! Thinner than ones on carts.

Has anyone had any luck with fixing video on this system?


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PostPosted: Mon Sep 26, 2005 7:59 pm 
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leonk wrote:
- the top loader / front loader have the same CPU and exact same PPU


Actually, this is not true - from numerous reports, frontloaders use an RP2C02G PPU while toploaders use an RP2C02H, and this is reported to be part of the problem.

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PostPosted: Mon Sep 26, 2005 8:31 pm 
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Quietust wrote:
leonk wrote:
- the top loader / front loader have the same CPU and exact same PPU


Actually, this is not true - from numerous reports, frontloaders use an RP2C02G PPU while toploaders use an RP2C02H, and this is reported to be part of the problem.


I will confirm tomorrow.. but when I did compare the 2 this past weekend, they were identical.


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PostPosted: Mon Sep 26, 2005 9:59 pm 
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My Famicom AV doesn't have the problem and is extremely similar to the Top Loader in design. It uses a RP2C02H and the traces are likely equally thin to the Front Loader. It could be the chip, PCB layout, a circuit board mistake or poor quality parts being used.

Has anyone ever used a SNES power supply? Maybe the NES-001 power supply just isn't well-suited to the Top Loader. You may get a better picture if you can use a power supply with the same specs. My Famicom AV does.

What should be done is to take the video signal directly from the PPU pin and feed it through the video amplifier shown on the NES 001. If the problem still exists, then you can likely eliminate the PCB as a suspect and concentrate on the chip itself.


Last edited by Great Hierophant on Mon Aug 03, 2015 5:47 pm, edited 1 time in total.

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PostPosted: Wed Sep 28, 2005 3:06 pm 
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Well folks.. here's what I found out.

My NES-101 (top loader) has the following:

PPU - RP2C02G-0 (3CM 37)
CPU - RP2A03G (3CM 10)

My NES-001 (front loader) has the following:

PPU - RP2C02G-0 (9G2 13)
CPU - RP2A03G (9G1 24)

I can take pictures of the PCB's for those of you that don't trust me, but the problem is NOT with the PPU as previously suspected! My top loader has a front loader PPU from the factory, yet still has the "jail bars" on the RF output.

It's something else.

Anyone care to share PCB pictures of the AV famicom?


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PostPosted: Wed Sep 28, 2005 3:40 pm 
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Last edited by loopy on Wed Aug 20, 2008 10:57 am, edited 2 times in total.

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PostPosted: Wed Sep 28, 2005 3:49 pm 
Is that AV famicom???

It seems to have the 'H' PPU which makes me believe it's actually a US top loader.


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PostPosted: Wed Sep 28, 2005 4:07 pm 
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Last edited by loopy on Wed Aug 20, 2008 10:57 am, edited 1 time in total.

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PostPosted: Wed Sep 28, 2005 7:52 pm 
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While we have a picture of the AV Famicom's guts, can anyone tell me what the Nintendo branded chip does? Also, why do the PCB traces seem to be masked? Is one side of the board used more often than the other side?


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PostPosted: Wed Sep 28, 2005 10:07 pm 
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Great Hierophant wrote:
While we have a picture of the AV Famicom's guts, can anyone tell me what the Nintendo branded chip does? Also, why do the PCB traces seem to be masked? Is one side of the board used more often than the other side?

I'm not sure, but I would guess the Nintendo chip is the CIC. As far as the traces, they are definatley not "masked". This board is much smaller than the original. Notice that there is not much surface space on the board left, since it's almost entirely covered with parts. All the interconnecting traces are done on internal layers of the board.


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PostPosted: Wed Sep 28, 2005 10:19 pm 
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Last edited by loopy on Wed Aug 20, 2008 10:57 am, edited 1 time in total.

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PostPosted: Wed Sep 28, 2005 10:21 pm 
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teaguecl wrote:
Great Hierophant wrote:
While we have a picture of the AV Famicom's guts, can anyone tell me what the Nintendo branded chip does? Also, why do the PCB traces seem to be masked? Is one side of the board used more often than the other side?

I'm not sure, but I would guess the Nintendo chip is the CIC.


It can't be, for 2 reasons:

1. It's 32 pins! The CIC is only 16 pins.
2. The Famicom never had a lockout chip in the first place.

My guess is that it contains the logic of the two 74368s (for the controllers) and the 74139 (for address decoding).

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PostPosted: Wed Sep 28, 2005 10:48 pm 
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I'm inclined to agree. Here's why:

Above the 2A03 is "U6 CPU". Above the 2C02 is "U5 PPU". Above the mystery chip is "U3JIO" which I took to mean "joystick I/O".


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PostPosted: Thu Sep 29, 2005 2:36 am 
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Someone recently sent me the pinout for this chip. I just haven't added it to the site yet.

http://nesdev.com/nes_pio_pinout.txt


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PostPosted: Thu Sep 29, 2005 5:48 am 
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hmm...

it's difficult to compare the top loader USA to the famicom AV.. the layout is completly different and some of the IC's are also different.

Maybe what we should do is trace pin 22 (video out) all the way to the RF out and compare that to the front loader?

Also, I've noticed that the famicom top loader has a few more electrolitic caps (which the US one does not). The vertical bars I notice on the output reminds me of the "jail bars" one sees when their arcade monitor needs a new cap kit!

Has anyone tried adding the "missing" caps? and if so.. what did you do?


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