13.3) To fix an automatic level select problem:
One possible piece which can be blown by static electricity at the controller ports (see 10.2) is the SN74LS541N chip, a 3-to-8 decoder. If this is the chip that's
blown, then replacing this chip (a generic component, available at any good electronics store) can solve the problem. - 13, 15
Parts:
A good soldering iron (with a very thin tip) Computer solder (thin) Solder wick Needle nose pliers An SN74LS541N chip Two 2.2K K27 resistor packets
(optional/recommended)
Getting started:
Plug in and turn on the Coleco with a Donkey Kong cart inserted. When the game automatically goes into play mode, note if the Mario moves without touching the
joystick. If so, then the 1st player chip is definitely damaged. If a two player game is the one automatically started (which seems to be the prevalent fail mode)
automatic movement of the second player's Mario likewise indicates that the 2nd player chip is certainly damaged. Lack of automatic movement does not rule out
the possibility that either or both chips are damaged; indeed, given the automatic select problem, it's likely that at least one chip is damaged. But determining that one
chip is certainly damaged can minimize your work.
Surgery:
1) Turn off and unplug your ColecoVision, removing the cartridge.
2) Make certain that you are properly grounded, if possible.
3) Open the plastic casing for the unit.
4) Remove the metal cover from the board by desoldering it. It just gets in the way so its better to remove it. It is not essential to the working of the game, though it
can be resoldered later if desired.
5) the bare board upside down and find the soldering connections for the SN74LS541N chip that you wish to replace.
6) Note the orientation of the SN74LS541N you intend to replace, so that you can be certain that you provide the same orientation for the replacement chip.
7) Take the soldering iron and solder wick. Place the wick on one of the solder connections on the board. Press the solder iron on the wick. The iron will heat up the
wick which will heat up the solder. The solder will turn liquid and be absorbed by the wick. This takes some practice before you get the hang of it.
8) Absorb as much of the solder as possible from all of the connections to the chip you're removing as possible.
9) Flip the board back over and take the pliers. This is where you have to get tough with your Coleco, and let it know who's boss! Growl at it occasionally to let off
steam. Now, being careful not to harm any other components on the board, grip the defective chip with the pliers and pull and pry. It's OK to break the chip
because it's defective garbage anyway.
*** Note - it's a good idea to wiffle each of the pins to pop them off any remaining solder. In fact, if the chip really is dead, it's better to just snip or Dremel all the
pins off first, _then_ desolder the pins individually. - 29
10) After forcibly removing bits of the defective chip from the board, remove any broken pins stuck in the board, extra solder, etc. so that the area that was
occupied by that chip is clean. Suck up the solder from the pinholes with the wick so that you can see right through the board through each pinhole. Gee, your
ColecoVision never looked better!
11) Take the new SN74LS541N chip and gently install it in the board, inserting the pins in the pinholes. Make sure that the chip is oriented in the same direction that
the original chip was! Gently bend the pins if necessary so that they all go in the holes. Be careful not to press too hard as you might bend some pins that aren't
properly aligned with their holes.
12) Flip the board over. Take the solder iron and the computer solder and solder each connection carefully. Isn't this fun? Don't you feel like a computer technician
now?
13) Optional/recommended: Replace the resistor packets on the port in a similar (though much easier) manner. For these parts, note the DOT orientation when
replacing.
14) Put the board back in the plastic case to avoid shock.
A couple of strange CV problems
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