Technical and Repair Assistance

[dreddnott]

I bought a Famicom at a local thrift store for about $7 today without the AC adapter. It came with one cartridge, the standard 4-in-1 with Super Mario Bros, 1942 etc.

I did some research and found that my American SNES power adapter has the correct output voltage, amperage, and polarity (center negative), but since the plug type was different, I wired up a temporary adapter to use.

While fiddling around with the adapter and the Famicom I managed to reverse the polarity for just a few seconds, long enough to smell the classic smell of burning electronics.

I tested the AN7805 regulator with a voltmeter, as that seemed to be the damaged component, and I get good positive DC voltage from Input to Common but only half a volt from Output to Common whether I have the power switched on or not. I suppose that getting positive DC voltage into the Common wire was fatal to the voltage regulator. None of the capacitors have burst.

In the process of doing this test I also figured out why the TV never showed a signal even before I accidentally switched the wires - some brutal klutz had snipped a few capacitors and resistors and run a wire across two leads on the bottom and put a pot on another two. I suppose he might have been attempting to repair or mod it, but the AV mod doesn't mess with those circuits at all, and the CPU board itself is pristine as far as I can tell.

Below I have posted four detailed images of the circuit board - in the last image there is a place for a capacitor labeled "C30" but no capacitor is present. Not sure if it's supposed to have one there as I don't have another for reference.


Picture of the power board

Detail of the added wire and pot

Inside the cage you can see a snipped resistor and snipped capacitors

The phantom C30 capacitor

[japanfreak]

Thanks... maybe one of our two DVD players can handle it...

[nintendodork]

(reply to dreaddnott)
I really don't think you should do that

Thanks... maybe one of our two DVD players can handle it...

Oh, and you need a VCR/DVD player, or just a standard VCR player, since I don't think that DVD players have the same outputs/inputs as a VCR.  Correct me if I'm wrong, anyone.

[133MHz]

dreddnott:

It looks like somebody modded your Famicom so that it would broadcast in a US channel frequency. That 'pot' you see soldered underneath the board is a variable capacitor, probably used to fine-tune the output frequency.

After replacing the 7805, try your Famicom in a TV capable of automatic channel programming and see if it finds the Famicom's channel.

[jimhmphry]

  just won a super famicom will a reg famicom ac plug work with it  i've heard that a snes will work with it thanks.

[ckenda1]

Jim,

The SFC AC and the FC AC are identical.  It will work just fine.

DO NOT use a SNES AC plug.

[cosmic-ark]

Hi i am trying to get my famicom to work on an australian tv  anyway it has these wires that have been attached for what purpose i dont know anyway since i cant get it to work i was thinking of cutting them off can anyone advise what these wires may have been put there for thanks

[133MHz]

Pic is extremely blurry

[cosmic-ark]

sorry try this pic  my famicom never came with one of those little boxes either would that be the reason i do get a black screen when i search for a signal any help would be appreciated thanks

[133MHz]

Your Famicom's RF modulator board has been replaced (see the MAKKO TOYS LTD branding on the board? That's not the original one).
This is probably an AV mod, or a NTSC-M mod (to make the Famicom transmit on US Channels 2, 3 or 4).

Does anybody have more information about the MAKKO TOYS stuff?

[cosmic-ark]

thanks that would explain why it doesnt have the channel1-2 switch on the back i guess i better leave those wires in place still no closer to getting it to work looks like i will have to get a nes toploader for the fds

[Lolmann]

Yeah i got 2 games the one to the right (TinyToon Adventures) starts with a grey screen even though i blow on the connector pins and the other one (Hook) is fucked up all graphics becomes corrupted

[Byron]

I assume you've already tried rubbing alcohol on a Q-Tip. Look at the connectors and see if there's any green corrosion. Alcohol wouldn't remove that, but fine sandpaper or an abrasive cleaner will.

If the connectors are clean and undamaged, I don't know if there's anything you can do to repair a damaged chip.

[JC]

Whoa...so I just got a new multicart. I popped it in to play, and after a few minutes of Samurai Showdown II, it started smoking. I pulled the cart out and it stayed smoking for about a minute after. Looked inside and nothing seems amiss. Any ideas?

[LocalToast]

Black. Magic.