So, at some point I will have to try modding my newer Famicom which has GPM board inside.
This seems to be the guide: http://jpx72.detailne.sk/modd_files/fc/avmod.htm
However, I have question regarding parts. I have 120R and 200R resistors and the guide expects 100R and 150R, how exact this has to be, can I use 120R in both locations or do I need to get correct ones from eBay etc ? Also there are mentions about 33uf resistor in the guide, I assume it reall means capacitor? If so, again, I have 47uf 16V capacitor, can it be used instead?
µF means microfarad, thus capacitor.
By using parts out of spec, the end result of the mod will appear different from what is typically described. It may not be a whole lot though.
OK, but the differences are not likely to cause any damages to components, they have some tolerance etc ?
I used that mod instead the results are satisfying https://playoffline.wordpress.com/mod/oldfcfba/
I suggest you not to disable RF functionality :) I already moded 2 consoles
here are my results : http://www.famicomworld.com/forum/index.php?topic=12059.0
OK, I proceeded with the original mod, mentioned in the first message.
I get no sound and no video, the only thing which happens when I switch power on is that the constant hum heard from the TV speakers changes tone, that's it.
I was having some troubles soldering to pin 22, I couldn't get it to stick so I rebuilt the whole the on the backside of the board, carefully checking to connect to correct pins, B from transistor is connected via cable to pin 21 which is lifted and has no contact with motherboard. I have used 120R resistors and 47uf capacitor so as mentioned the parts are not exactly the same, 1uf ceramic caps I had.
I wonder if the transistor got damaged, or I made some soldering mistakes or it's simply because all parts are no correct. I tried to solder RCA connector to the negative pin of the 47uf cap to test video and then tried soldering it to pin 46 to test sound. No video, no audio, except that buzz / hum whatever.
Any suggestions?
If you could post some pictures, that would help people work out what's going on :)
Yes, here are some pics. I actually removed all mods and redid it on the component side.
http://i6.aijaa.com/b/00401/13945753.jpg
http://i3.aijaa.com/b/00609/13945754.jpg
If I connect the Famicom to TV with audio pin, I instantly get some buzz from TV speakers and when powering on the hum changes tone. Clearly there's something wrong as my succesfully modded Fami does not do that.
EDIT: The resistor nearby PPU might have been damaged slightly during the soldering process?
EDIT2: During the difficulties of soldering to pin 22, could it be possible that I have created short circuit under the PPU or something, so should the PPU be removed? I have solder sucker so maybe I could do it altough I expect t to be tedious process.
EDIT3: Removed transistor and tried to test it with multimeter, never tested transistor before, but if I put to test mode I get readings when the prongs are like this:
http://aijaa.com/cLEUdp
Shows around 770. If I move negative lead to the third pin I don't get reading.
EDIT4: If I put negative on the first pin (counting from left of course) and positive to the third I get around 780.
When you do soldering, use some flux, please. I very doubt, that you killed PPU(except ESD), but transistor.
OK, I see that same model transistors are sold on eBay so maybe I'll try with new one.
Is the constant buzzing sound a clear indicator of failed transistor?
EDIT: Pressing reset switch also alters the tone so apparently it works and is not shorted etc.
Test for the shortcuts is the first thing, which you have to do(especially with your soldering). Also check 5V on the pcb.
ANY PNP general low power silicon transistor will work.
Measured power button contacts, around 5v when off, measure ppu pins, around 5v when on. Noticed that CPU does heat up if I leave the console on for a while, will check if PPU does the same.
EDIT: Also measured CPU and cartridge connector, all show 5V.
If the PPU is dead, where can it be bought at reasonable price? Found some on Aliexpress, but in lots, one seller was also claimed to sell fakes which is of course "great"..
EDIT2: I already ordered replacement transistor.
Did you ordered flux?
Remove everything and start again would be my only advice. Did you confirm if the board worked before you started working on it?
Flux I didn't yet order.
Yes the Famicom worked fine and I was able to play with shitty image quality but perfect sound by hooking it first to VCR.
Yeah, I did restart once already.
You should be able to get sound output...hookup an alligator clip to an centre pin of rca cable and pin 46 of cartridge connector and another alligator clip to ground on rc cable to emshield on famicom board and hook rca cable into tv. If you don't hear famicom music get another board.
Like 80sFREAK said,get some flux dude and I would also get some desoldering braid.
OK, I'll have to try your suggestions later, I'm not currently where the Famicom is.
However, I still think that there is small change that I damaged the PPU when soldering, look this photo which I took with earlier mod attempt:
http://imgset.net/zNezhP
The black stuff is definetely from the PPU. There is not bits missing but clearly the soldering iron touched the PPU for some time. The reason there is wire going under the motherboard is because I was having lots of troubles soldering into pin 22. But later I started from scratch and the mod is currently more like it's supposed to be in terms of component placing etc.
And is it possible that some solder got under the PPU, possible causing troubles? Transistor was mentioned as one cause and I did maybe use too much force when removing it.
I don't want to be a dick, but that soldering is terrible. Are those pins on the transistor connected together? It's hard to see what's going on with those huge blobs of solder everywhere, I'd get some de-soldering braid/a solder sucker to remove everything and start again. Try the suggestion from hvc01 to see if you can at least get sound so you know whether the board's actually working. I found it useful to practice removing components and soldering connections on an old computer motherboard, and watched some Youtube tutorials when I was learning. You should not need any force to remove the transistor from the board if you do it properly :)
I'm not offended, I know my soldering is not good. I redid the mod so the pic which I posted last is not the current situation.
I don't have alligator clips and to be honest I don't know what ems shield is.
However, here is audio recording about this Famicom:
https://clyp.it/qj0uqwsk
RCA connector soldered to pin 46.
1) Famicom hooked to TV without power supply
2) Power supply hooked to Famicom but not to the wall
3) Power supply hooked to wall
4) Famicom powered on
and then everything in reverse.
EDIT: Okay now I get it. I left the RCA plugged to TV, switched on Famicom, then got another RCA cable, touched the metal part on the back of Famicom with one end and other end to the another RCA cable's outer ring, I get sound!
https://clyp.it/du3r5jpd
Ummm... did you connected shield of the cable(outer part of RCA) to the pcb's ground?
Quote from: Finfami on August 28, 2015, 08:04:03 am
EDIT: Okay now I get it. I left the RCA plugged to TV, switched on Famicom, then got another RCA cable, touched the metal part on the back of Famicom with one end and other end to the another RCA cable's outer ring, I get sound!
https://clyp.it/du3r5jpd
OK, that's good :)
You can do a similar thing with the video, ground the outer ring and touch it to pin 21 on the PPU (the one you've been soldering on to), you should get some kind of video output. It won't look great, but if that works then you know the PPU isn't toast.
Goddamn, did the same thing for video and there it is....
The guide did mention that I need shielded cable for video, I however assumed that I can get audio the same way as with that another mod, soldering simple cable to pin 46.
Because I had difficulties with the mod, I was trying to test if I get even sound from the Famicom, after I heard only buzzing I was almost certain the Famicom was dead, until after measuring etc. started to have some hope.
As for jailbars, I think the image quality is very good, I'm using 40" TVT and they are very very faint. There is however some sort of horizontal interference going on:
https://www.youtube.com/watch?v=BuBZzCisvYo
I am using very long RCA cable which I assume could contribute something, in addition of this "trick" I'm using to even get video at the moment?
So the whole problem was an open circuit with no ground. He shoots he scores! Good work. At least you have fixed it. 😃
Yeah... I assume that was very basic thing, I probably should research some basics....
But now the mod is finished and the Famicom works fine. I see many people opt to put rca jacks on the side of the console, for shorter wires I assume.. I had only one rca jack so I did the same thing as with first Famicom I modded, used the existing one and added one for audio. Ports on back. Even though this Famicom is newer than the first one the plastic has yellowed and it overall feels like cheaper quality, it is much weaker which I noticed when modifying the case for rca jack.