AV Mod Help

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

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HanStrikesBack
Posts: 2
Joined: Thu Jul 08, 2021 4:26 am

AV Mod Help

Post by HanStrikesBack »

Hello,

I tried doing an AV mod on a famicom, I copied JPX72's method on his site. Problem is it only gave a me a static and fuzzy screen. I redid everything from the start but it's still the same issue.

Anyways, if it can't be fixed, how can I pull out the cartridge connector? I tried using a manual solder sucker on it but it's still stuck on the board. Any help would be appreciated.

https://drive.google.com/folderview?id= ... X8y4nKQdtz

Link of pics and vids of mod.
lidnariq
Posts: 11429
Joined: Sun Apr 13, 2008 11:12 am

Re: AV Mod Help

Post by lidnariq »

I think you may have roasted the transistor when you de- and re- soldered it. It's nothing special, just a high-ish gain PNP transistor.

Your video output is close to right - hence why there's visible curvy lines.
HanStrikesBack
Posts: 2
Joined: Thu Jul 08, 2021 4:26 am

Re: AV Mod Help

Post by HanStrikesBack »

lidnariq wrote: Thu Jul 08, 2021 12:16 pm I think you may have roasted the transistor when you de- and re- soldered it. It's nothing special, just a high-ish gain PNP transistor.

Your video output is close to right - hence why there's visible curvy lines.

I tried using a brand new transistor also but I still get the same result. You have any other suggestions? I'm thinking of trying a different circuit.

What do you mean by close to right? Is there something wrong with my solder?

Thanks.
lidnariq
Posts: 11429
Joined: Sun Apr 13, 2008 11:12 am

Re: AV Mod Help

Post by lidnariq »

You see the diagonally-sheared images and weird curvy lines that show up in your video? That implies that it's very close to valid, but in a way that your TV doesn't understand.

I'm unfortunately not feeling clever enough to have guesses of what else to try. Maybe in a day or two I'll have some inspiration.
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Ben Boldt
Posts: 1148
Joined: Tue Mar 22, 2016 8:27 pm
Location: Minnesota, USA

Re: AV Mod Help

Post by Ben Boldt »

I am not familiar with the circuit you are mentioning, but I noticed that you did not connect the GND on your video cable:
gnd.png
Please post a link to your circuit here and we can double-check. I am used to using this cicruit:

Code: Select all

[+5V]---------/\/\/-----+
 |             300      |
 |+                     |       +
--- Tantalum            +---------|(---------/\/\/-------+--------+
--- 4.7-47uF           /     Electrolytic     110        |        |   Pin
 |               (b) |L (e)      220uF                   |        +----O } Composite
 |  [PPU.21]---------| PNP                      Ceramic ---              }   Video
 |                   |\ (c) 2SA937                560pF ---       +----O }
 |                     \                                 |        |  Ring
[PPU.20]----------------+--------------------------------+--------+
[GND]
It it also here in the wiki:

https://wiki.nesdev.org/w/index.php?tit ... deo_Output

You can substitute a 2N3906 instead of the 2SA937, though note that they have a different pinout.

Code: Select all

  2sa937        2n3906
 __ ______       ___
 | V     |      /___\
 |_______|      |   |
  |  |  |       |___|
  |  |  |       _|||_
  E  C  B      |  |  |
               |  |  |
               E  B  C
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