Technical and Repair Assistance

[wolf9545]

You can just take the composite video wire and touch it to the video points on the board. The image will be dark and washed out, but it will be enough proof that the Famicom is working.

So I took and connected the center pin on the video cable and touched it to IN1 and then IN2 (one at a time).  Then I connected the outer ring on the video cable to the metal shielding on the RF board.  Plugged the famicom in and turned it on with a game in it and nothing.

I am wondering if there is a problem with the RF board.  Any way of testing it to make sure the components are good?

Picture came from: http://www.famicomworld.com/Workshop/AV_Mod.htm

[133MHz]

Sounds like your Famicom is dead. Are you sure it's getting power? The RF board could be energized but that doesn't mean that the logic board is getting power.

[wolf9545]

I tested the AC adapter and I am getting somewhere around 16V coming out of it and a few amps.  It is the correct AC adapter for the famicom.  Could one of the capacitors be shot and stopping the voltage?

[133MHz]

The 7805 regulator could be bad. You should have 5V between the rightmost pin and ground.

[wolf9545]

I replaced the 7805 with a new one from Radioshack.  Tested the voltage on the pins and got only a few mili-volts.  I tried following the path starting where you plug the ac adapter into the unit.  I came across a capacitor and when measuring the voltage from ground to one side of the cap the voltage was close to the 16 but was dropping quickly.  I can not tell what the rating is on the cap because of the metal shielding around the RF side.  Anyone have the ratings on the capacitors so I can try replacing them?

[133MHz]

You clearly said that you're not getting any significant voltage on the 7805, there's your problem.
Capacitors shouldn't cause problems unless they have visibly exploded and/or leak electrolyte.
Maybe you've got a defective power switch, or something else in the path.

[wolf9545]

Thank you for your help so far.
I know the power swith works because with the unit unplugged, I used the ohm setting on my meter and with the power switch in the on position I get a "closed" reading on my meter.

Well, if it is the board is anyone willing to donate/sell a working famicom board?

[ericj]

Have you tried re-flowing the solder on the PS board? Could just be a cold solder joint somewhere.

[wolf9545]

I tried taking my soldering iron and re-heating the larger areas of solder on the PS board.  What is odd is on some of them when I re-heated them a brown/orange bubbles came out from under them.  It looked almost like it was old dried flux.

[133MHz]

It looked almost like it was old dried flux.

That's because it IS old dried flux

[wolf9545]

I was talking to a guy at a local flea market who knows his stuff about old systems.  During the week he looked into my problem a bit and he said that cap 402 and 404 were leaking.  Does the numbers sound right?  I found a schematic for the famicom but don't see those on there.  He also said that they are hard to find.

[133MHz]

Pics? Also most caps in a Famicom aren't critical about their exact values (except for those in the video output section, different values would change how the picture is displayed). If they're power or noise rejecting related there shouldn't be any problems with putting higher value caps in their place.

[wolf9545]

What pics are you looking for?  I can take them after I am done with work.

[133MHz]

Well, pics of your Famicom board, RF board, especially around the suspect capacitors.

[wolf9545]

Well, pics of your Famicom board, RF board, especially around the suspect capacitors.

Well here are pics of my famicom; http://www.flickr.com/photos/7524204@N07/sets/72157606816472960/ .  I had to post them onto flickr because every time I tried to upload them here, even one file at a time, I was getting an error saying that the upload folder is full.  The one cap that I think might be having problems is in the picture of the RF board; it is the one that is to the right and up of the very large cap.  If you want more/better photos just let me know.