Famicom World

Family Computer => Technical & Repair Assistance => Topic started by: Finfami on August 20, 2015, 03:07:57 am

Title: About isolating PIN 21 on Famicom AV mod
Post by: Finfami on August 20, 2015, 03:07:57 am
I modded the older version of Famicom (with non gpm board). I have picture with jailbars, since english is not my main language I want to make sure one thing:

To reduce jailbars, if I remove connection of pin 21 to motherboard, do same for the transistor pin B and then wire them together, does that reduce jailbars or is more required? Based on what I've read the problem is in the morherboard, the trace picks up noise.
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: FAMICOM_87 on August 22, 2015, 06:38:31 pm
I reduced my jailbars by adding a cap between + and - rated 1000 mF  but  in tutorials they say that everything about 220 mF are good for that improvement
So solder one to + and - near PPU and see if there are any  improvement :)

In my case jailbars are barely noticeable, but I think it is safer than lifting pins
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: Finfami on August 23, 2015, 01:27:46 am
Sorry for being total noob, but where do I exactly solder the cap?

I have this motherboard: http://postimg.org/image/5ru3k867f/full/

EDIT: Looks like I only have used 1000uf capacitors in storage (short legs), I do have unused 1800uf 16v, 2200uf 10V and 3300uf 10V caps but they might not suitable, maybe the 1800uf is?
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: FAMICOM_87 on August 23, 2015, 09:19:25 am
all are good caps .
look my picture black cap on top is that one for reducing vertical lines in my case is 220mF but I replaced is with 1000 mF and there is a little improvement over 220 one   :) just spot + and -  :)
I did not try yet, but I will add one more cap in parallel near by in other + - 5v spot and see if there will be any more improvement .


http://i54.photobucket.com/albums/g113/IBMDOS/MODS/AV%20Famicom/PA300054_zpszahrwbwk.jpg~original

this is my AV mod
http://www.famicomworld.com/forum/index.php?topic=12059.0
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: Finfami on August 23, 2015, 09:57:32 am
Tried solderin 1800uf 16V to the spot where you have 220uf 16V cap on that picture but it didn't change anything  ???

Like this (not yet soldered in picture): http://aijaa.com/k8BBsU

I have this mod:

http://assemblergames.com/l/threads/guide-av-mod-your-famicom.49263/

But about the lifting, is it really that you basically lift the pin 21 and the one leg from the transistor and create new connection between them with a wire?

(http://i8.aijaa.com/b/00965/13942706.jpg)

Here is a pic of the jailbars I now have:

http://aijaa.com/klxnHW

40" FullHD TV, I assume TV type and color settings make some difference as well.
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: FAMICOM_87 on August 23, 2015, 01:17:40 pm
I am with 14" CRT may be because of that I cannot notice those vertical lines as you.
so you tryed with that cap and there is now difference .. hmm strange there must be a improvement at least little.

Hm may be try this, put only caps , on bottom of page , if it is no with satisfying results than follow the mod by lifting that pin 21 and solder it to that transistor pin like in the that mod

http://vaot.mydns.jp/fc/noise5.htm

I forgot to mention that I uset this mod https://playoffline.wordpress.com/mod/oldfcfba/



Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: hvc01 on August 23, 2015, 01:45:08 pm
The picture looks good. Jailbairs unfortunately you have to accept ☺
Title: Re: About isolating PIN 21 on Famicom AV mod
Post by: FAMICOM_87 on August 23, 2015, 05:03:41 pm
Quote from: Finfami on August 23, 2015, 01:27:46 am
I have this motherboard: http://postimg.org/image/5ru3k867f/full/


wow I just noticed that your CPU is UMC, so trange it must be Ricoh like your  PPU