NES Repairs               (rev. 0.3 22-Sep-97)
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MANY so-called "faulty" NES consoles are not really broken. They just need
cleaning inside, and possibly a small "adjustment". You might be interested to
know the following if your original design NES is not working properly. The
typical symptom is a blank screen, with the console resetting repeatedly.

This document is written by Mark <mark_k@iname.com>. Mail me if you have any
comments or suggestions. This document is freely distributable. You can
download the latest version from
                  http://www.netcomuk.co.uk/~markk/index.html

Here's my theory on this. When a game pak is inserted into the NES and pressed
down into position, the connector inside the NES flexes slightly, both where it
touches the game pak and where it touches the circuit board inside the NES.
Over several years the effect may be to oxidise some of the metal on the NES
PCB edge connector contacts, to the extent that the lockout chip no longer
functions. This causes the flashing screen. The use of accessories like Game
Genie and Pro Action Replay may contribute towards this; the action of
inserting these may tend to push the connector back slightly, or at least cause
it to flex more.

The contacts which touch the game pak connector can also become slightly bent
from their original positions, so that they don't make firm contact with the
game pak. This usually happens with old consoles which have been used a lot.
This problem is likely to happen sooner if you leave game paks in the NES for
extended periods of time (e.g. when the console is switched off), or use a Game
Genie-like accessory often.


First try using a NES Cleaning Kit. Clean all your game paks, as well as the
console connector. If this doesn't help, do the following:

1. Open the NES case by removing the six screws in the base.
2. Lift off the lid and remove the top part of the metal shielding. The
   shielding is attached by seven screws.
3. Remove all other screws which attach the NES PCB to the base of the case.
4. Gently lift up the PCB and bottom shielding. You may want to temporarily
   disconnect the power and controller PCB connectors.
5. Unscrew the top part of the black plastic cartridge tray, and slide it
   forward and away.
6. Now you should be able to see the NES game pak connector, which is attached
   to an edge connector on the main PCB. Remove this. It's quite a tight fit.
   Pull it evenly, parallel with the main PCB.
7. Using cotton wool buds and isopropyl alcohol, thoroughly clean the edge
   connector on the main PCB. You should find that a surprisingly large amount
   of black dirt comes off. I find that moving up and down along each contact,
   gradually moving along gets most dirt off.
8. You can also use the cleaning bit from your NES Cleaning Kit to clean the
   part of the black plastic connector which mates with the NES PCB edge
   connector. You need to take the bit out of its case to do this.
9. Put everything back together again, making sure that the game pak connector
   is firmly seated on the PCB.

If this doesn't cure the problem, it could be that the contacts which touch the
game pak are bent. If so, you can try the following:

1. Straighten out a paper clip. Grip onto 1-2mm at the end of the wire with a
   pair of pliers, and bend the rest around to a right angle.
2. Use this makeshift "hook" to try and get behind each of the lower contacts
   and bend them up slightly. This is very tricky, and may not work, but it is
   worth trying.


If all this doesn't improve matters, you need a new connector. A company called
MCM Electronics in the US sell these. I believe their price is around $8.00. It
may be cheaper to find a working or faulty used NES, and take the connector
from that (but if you buy a faulty one, try to ensure that it doesn't have the
same fault).

As a temporary measure, you may find that using a Game Genie or similar helps -
the thicker PCB of the Game Genie presses more firmly against the contacts in
the console.

You may also find that if you press a game cartridge right down and hold it
there, and then turn on, that it works. So you could jam something above the
game pak drawer and below the metal shielding, to keep game paks fully pressed
down while you are playing.



I have fixed four "faulty" NES consoles in this way. This is probably the most
common fault.

Even though the original design NES does have a problem with dirt, I prefer
this style of connector to the conventional one. At least the contacts on your
cartridges can't get worn away easily.

To prolong the life of your NES, never leave a game pak inserted when you are
not playing. If you do, the contacts inside the console are bent for a long
period. Over time, they will gradually lose their ability to spring back fully.
This leads to the problem described above.

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