Technical and Repair Assistance

[Ruthenium]

It was on the previous page, but:

Edit: between not having an AC adapter and not powering up, it looks like I'm going to have to leave my first negative feedback on ebay.
EDIT2: If there's nobody that can help me fix this, then Who am I supposed to sell this to? I don't know of any collector that will buy a broken famicom.

[ericj]

Got Ruthenium's Famicom in the mail today to test it out. Good thing is that it is getting power on both boards. Most likely the A/V mod is where the problem is at.

133MHz, any chance you see something that I'm not seeing that is wrong with the current mod before I redo it? I checked the cables and they have continuity, so they're ok, although not great quality. Also, I'm a little confused why the A/V cables are only connected to the RF/PS board. Thoughts?

[133MHz]

That kind of AV mod is weird, but you should get some kind of picture and sound. The video signal will be unamplified and the audio will have a DC offset, but it should display something recognizable. Better redo the mod anyway.

My Famicom came with a similar mod (wires directly soldered to the Audio and Video points - and a resistor or two in series with them). The picture was really dark and my TVs had a very hard time trying to sync to the video signal. The wires, resistors and connectors were really old too, so this was probably done back in the day. I don't know why we keep finding this old mod if it doesn't work, maybe there are TVs out there that can display such an out-of-spec composite video signal? Japanese TVs probably?

You say you've got power on both boards. Is it the unregulated voltage that goes to the power switch or is it the regulated +5V supply from the output of the 7805?

[ericj]

Thanks for your input. 
I'll work on redoing it this week with new rca cables and hopefully it will work. I'll keep you posted.

[133MHz]

This might sound trivial and not even worth asking, but have you tried reversing the RCA leads? Maybe the colors of the connectors are incorrect and you're "listening" to the video signal (composite video makes for a neat buzzing sound).

In case you've already tried, sorry for asking such a dumb thing.

[ericj]

I just finished the av mod on Ruthenium's Famicom and it's working with picture & great sound using 133MHz's schematic. While the picture is in color and stable, the colors are a bit muted. The Famicom has the board revision with the VIDEO, VCC, SOU, etc. points marked on it. I'm tapping the video from the VIDEO point. Is there a different place I should try? I'm using a 2N2222 transistor but otherwise, all the resistors and caps are as noted on the schematic.

[133MHz]

Try varying the 75Ω resistor's value. If the picutre is too white try increasing it a bit.

[ericj]

I'll grab a 100ohm resistor tomorrow and try it out. Thanks, 133MHz! 

[MS-DOS4]

Hey, I blew a cap on my famicom. Am I screwed?

A little dusty, but fine.




Blown:



No discoloration on the chips:


Do you think if I replace the cap with a duplicate from Radio Shack, will my famicom operate? (I've never gotten this thing to work, It could have been blown when I bought it. I just looked under the hood today.)

Also, I heard somewhere that there was a fuse in this thing, but I can't seem to find it. Is there truly a fuse in famicoms?

[133MHz]

The big one? That's the main filter capacitor. Not hard to find and not expensive, also its value is not critical (as in you can replace it with a higher voltage/capacity cap in case you don't find an exact replacement). By all means replace it.

Some Famicom RF modulator boards have a fuse, but not a standard glass one. It looks like a black rectangle with radial leads. It can't be seen from the angle of your pictures.

Try to take a picture from the side of the blown capacitor and one from the underside of the board.

[MS-DOS4]

[133MHz]

Your pictures are great! Very sharp and excellent lighting. It's not easy to photograph printed circuit boards and having the circuit traces turn up so clear and detailed. My hat's off to you, sir!

Your Famicom doesn't have a fuse, which means that not only the main filter capacitor is blown, also the 7805 voltage regulator is dead. Replace both and your Famicom should be back in business!

Also I have noticed that the capacitor's rating is 1000µF 6.3V
This is incorrect (which means that this capacitor has been replaced before). Its voltage rating is too low, which is why it blew up. If you replace it with the same type, it's going to blow up again.
Replace it with a 1000µF, 16 or 25 V electrolytic capacitor and your problems will be over. Remember to respect the polarity!

[MS-DOS4]

Thank you very much! I'll buy those parts you talked about and hope for the best.

I can't tell if your using sarcasm there with the pictures though, they're mostly out of focus. I can't seem to find the manual focus on my camera.

[133MHz]

Long story short, buy these:

• 7805 Voltage Regulator IC


• 1000µF 16 or 25V Electrolytic Capacitor

Wish you the best of luck with reviving your Famicom!

[Rogles]

I don't think he's being sarcastic; those are nice pictures.