NES with broken powersupply/RF-box

[per]

I recently bought a NTSC NES to play some of the games I have in their original speed.

So, I received the unit, and plugged it in. I turned it on, expected at least something, but nothing happened. After a quick check with a multimeter, it turned out that the fuse in the power transformator had blown.

I replaced the fuse, but still nothing. I opened the RF-box, and there I found one of the worst soldering patches I have ever seen. I removed the bad patch and verified that the diodes in the AC/DC converter worked, but it was still not showing any sign of life when I tried to power it on again. Another check turned up that now the diodes were gone too, and I decided to run DC directly through the 7805.

For some reason, it actually powered up when using DC directly on the 7805. I then tried it with our TV. I did get a picture of the game running, but the sound had quite a lot of that 50Hz AC noise in it. The picture also had lines of darker/ligther colour, which I guess is due to the same noise (or that our TV isn't compatible with NTSC, something I doubt since the colors and sync are processed right). I don't know if it's the DC-transformator or just external noise, but it sure is annoying.

In comparasion; the AC adapter for the NES usually outputs something like around 12VAC. The DC adapter I used outputs around 13VDC, but the 7805 rues it down to 5VDC anyways.

So what can I do to fix this thing? Should I just buy a new unit (may cost me up to $75), should I attempt a repair myself, or should I try to send it to an electronics expert for repair?

 

[ahm]

In comparasion; the AC adapter for the NES usually outputs something like around 12VAC.

I'm looking at the power supply for my (USA model) NES and the output voltage is marked as 9VAC @ 1.3A
I wonder if you have the correct supply for your region?

 

[per]

I'm looking at the power supply for my (USA model) NES and the output voltage is marked as 9VAC @ 1.3A
I wonder if you have the correct supply for your region?

Yes, I think it's right. However, the general thing is that even it says 9VAC on the box, it meassures 12/13VAC with a multimeter. Even the unofficial schematics says 13V.

Anyways, I solved the problem by using another transformator. It's bigger, and rated at 6VDC @ 1A. All my multimeters does however read 11VDC when I meassure it. I made the fix permanent by opening up the RF box, isolating the AC->DC convertor/powerplug socket, then I wiered the powerplug socket directly to where the outputs of the AC->DC convertor originally went. Now I can power it with a normal DC powersource.

The only problem now is that the upper row of the 72-pin connector has problems making contact every time a new game is inserted. The lower row has already been altered by the previous owner, so reaching the back row with a small flatbladed screwdrive is next to impossible.

 

[Raven]

AHHH my post got erased....

Forgive the rushed-sounding writing style then, because I've got to rewrite the whole thing.

NES uses 800mA+ 9-13v just fine. The 72-pin cart connector is a common point of failure and you can buy replacements on eBay that are brand new due to this. Edit: Ex. http://cgi.ebay.com/NEW-NES-NINTEND...t=Video_Games_Accessories&hash=item27b17b120e

The RF modulator is an ordinary one, but you don't need one as there's a yellow/red RCA combo on the side of the unit which is much more accessible in a modern environment.

 

[per]

NES uses 800mA+ 9-13v just fine.

That must be why the first "direct-DC" attempt failed. That trnasformator was only rated for 400mA @ 9VDC (in reality; 13VDC).

 

[ahm]

However, the general thing is that even it says 9VAC on the box, it meassures 12/13VAC with a multimeter. Even the unofficial schematics says 13V.

Right. The difference can be accounted for by measuring without a load, versus with a load.

The only problem now is that the upper row of the 72-pin connector has problems making contact every time a new game is inserted. The lower row has already been altered by the previous owner, so reaching the back row with a small flatbladed screwdrive is next to impossible.

The 72-pin connector is replaceable. I bought mine for US$9 on eBay. And even if you're not going to replace it, it's useful to know that it can be easily removed from the PCB, allowing you to carefully adjust the pins. Of course, if it's too far gone, just replace it.

 

[Raven]

Make sure you clean your cartridges before using a new 72-pin connector, btw. I ignored that warning from everywhere and my new 72-pin connector became a crappy old one within a day - literally.