The ColecoVision power switch switch

[ArugulaZ]

The ColecoVision's power switch is the source of many of the system's woes. Twenty five years after it was manufactured, the lubrication inside the switch has dried up, making it difficult to flip on and off, and often resulting in issues with the games themselves.

The obvious solution would be to replace that switch with a new one, but I just don't know where to begin. I've removed the old switch and purchased a new rocking switch, but I don't know how to connect it. The new switch only has two posts, while the old one has at least six (possibly eight, although those might have been soldered in to stabilize the switch on the PCB).

Does anyone know how I can connect the new switch to the ColecoVision and make sure it functions properly?

[GonzoMPM-1]

The ColecoVision's power switch is the source of many of the system's woes. Twenty five years after it was manufactured, the lubrication inside the switch has dried up, making it difficult to flip on and off, and often resulting in issues with the games themselves.

The obvious solution would be to replace that switch with a new one, but I just don't know where to begin. I've removed the old switch and purchased a new rocking switch, but I don't know how to connect it. The new switch only has two posts, while the old one has at least six (possibly eight, although those might have been soldered in to stabilize the switch on the PCB).

Does anyone know how I can connect the new switch to the ColecoVision and make sure it functions properly?

Get rid of the switch you bought. It won't work. You need "double pull, single throw" that means it has two connectors and and one switch position for them. (It switches +5 and +12). most places sell one that will include the one you need. It will have 4 contacts.

If you get the right sized switch you can get it to work with the original external workings of the Colecovision on/off lever, by epoxying the new switch underneath it.

In any event, on the board, (looking down from the top with the switch in the lower left), you'll see:

Code: Select all

   ===  
 [     ]
 [ 1 2 ]
 [     ]
 [ 3 4 ]
 [     ]
 [ 5 6 ]
   === 

Connectors 1 and 3 are the +12 switching and 2 and 4 in my diagram switch the +5.

More precisely, pins 3 and 4 are tied to the +12 and +5 source, respectively, and pins 1 and 2 are tied to the +12 and +5 loads.

Make sure you get a switch rated for what the power supply says its putting out (I think about an amp in 5 volts).

[ArugulaZ]

Thanks! I got similar information from another forum, although the person there recommended that I use a double pull double throw switch. Right now I've got the console MacGyvered to run the moment it's plugged in, but as soon as I get a replacement switch, that will change.

[GonzoMPM-1]

Thanks! I got similar information from another forum, although the person there recommended that I use a double pull double throw switch. Right now I've got the console MacGyvered to run the moment it's plugged in, but as soon as I get a replacement switch, that will change.

The original switch _is_ DPDT, but if you flip the circuit board over you'll see that pins 3 and 4 are already tied to the other two unused pins (5 and 6).

I've personally installed DPST switches on several Colecovisions I've refurbished.

You may wish to consider desoldering, snipping, tinning and resoldering the power wires to the board, as corrosion in those connections seems prevalent.

Finally, if you use Ben's composite video mod, consider adding a 47uF capacitor followed by 75 ohms of resistance on the video out wire, right after the transistor, etc. This is called for by the data sheet for the integrated circuit Coleco used in the daughter board that combines the luma and chroma. The capacitor removes the DC component of the signal and the 75 ohms provides impedence matching.

[ArugulaZ]

Can I ask what this will do to the mod? Will it remove those annoying vertical stripes on the screen? If so I'll give it due consideration.

Also... I've been able to install the rocker switch without too much trouble, but I'm having trouble installing an indicator light. I've been able to get the lamp to light when the system is plugged in (regardless of whether or not it's turned on) and when the system is plugged in but turned off. How do I make it light when the system is plugged in and turned on? Will I need an XOR switch or another inverter?

Thanks for all the help, by the way. It's greatly appreciated!

[GonzoMPM-1]

Can I ask what this will do to the mod? Will it remove those annoying vertical stripes on the screen? If so I'll give it due consideration.

Also... I've been able to install the rocker switch without too much trouble, but I'm having trouble installing an indicator light. I've been able to get the lamp to light when the system is plugged in (regardless of whether or not it's turned on) and when the system is plugged in but turned off. How do I make it light when the system is plugged in and turned on? Will I need an XOR switch or another inverter?

Thanks for all the help, by the way. It's greatly appreciated!

It may well get rid of the vertical lines, my composite mods using this output stage are always VERY clear and clean. I've never had the verticle lines show up, but they could be a function of overvoltage or impedance problems.

You may as well try what I suggest, as it _IS_ spec for the chip on the coleco daughter board when preparing a composite output. As Ben's diagram and the experience of just about everyone shows, you may well get acceptable results without it, but if your TV or other display is sensitive to voltage or impedance matching you'll get some difficulties.

Try it. Its not hard, and if it doesn't work, you can remove it. You can literally unsolder the wire where you currently have the circuit hooked to your video out wire, and insert this with no problem:

It looks like this:

Code: Select all

[2n4401 AMPLIFIER OUTPUT ] >> ------- |( ----- /\/\/\ ---- >         [output]
                                      47uf      75 ohm       (to center connector of composite out jack)

(The "+" side of the capacitor hooks to the output of your amplifier, the "-" side hooks to the 75 ohms (two 150s in parallel will work), and then the resistors hook to the center pin of your video out jack).

Use a 16v 47uF capacitor and a 1/8 to 1/4 watt resistor.

To get an indicator light working, take a 100 ohm resistor off of "pin 2" in my diagram above (again, that's looking at the motherboard from the top down with the switch in the lower left), connect that to the positive lead on your LED, and drop your negative lead to ground. That will supply voltage only when its switched on.

If you're talking about a switch that has the indicator light built in, then I won't be able to help you without seeing the pinnout of the switch or how you've got it wired up.

[ArugulaZ]

All right, the lamp is lit! I've got everything working now, but I haven't tried adding the capacitor and resistor... mostly because i don't have them. I do have smaller capacitors (22uF, I believe?), but I'm guessing you can't put them in series to increase their effect the way you could with resistors.

Speaking of resistors, the smallest ones I've got are 22 Ohms. The rest range from 1000 Ohms to 450K Ohms (which I used for an earlier Atari 5200 mod). So I guess this mod won't be completely complete until I've got the spare cash for these parts, which will take about a month. Unemployment sucks!

[GonzoMPM-1]

All right, the lamp is lit! I've got everything working now, but I haven't tried adding the capacitor and resistor... mostly because i don't have them. I do have smaller capacitors (22uF, I believe?), but I'm guessing you can't put them in series to increase their effect the way you could with resistors.

Speaking of resistors, the smallest ones I've got are 22 Ohms. The rest range from 1000 Ohms to 450K Ohms (which I used for an earlier Atari 5200 mod). So I guess this mod won't be completely complete until I've got the spare cash for these parts, which will take about a month. Unemployment sucks!

If your capacitors are electrolytic (look like little cylinders) then it is likely that they're 22 uF. But if they're ceramic capacitors, then they're probably pico farads which are too small.

Lets assume they're electrolytic. If you put them in parallel ("+" to "+" and "-" to "-" then total capacitance is additive:




For reference, putting them in series causes capacitance to work as so:




Anyway, two of those 22s, if they are 22uf and not 22pF should be close enough, and if two in parallel don't work, three will certainly work becuase anything from 47 to 100uf is spec on that line.

As for the resistors, if you do have 22 ohm resistors, just put three in series which will get you close enough for gov't work and will at least provide you with a proof of concept.

(Note that you may need to adjust your potentiometer coming off the +12 source to compensate for the extra drag on the signal from the above, but it should be an overall much better signal).

Congrats on your work so far.

[ArugulaZ]

Nope, they're the disc-shaped ceramic variety. I was thinking I might be able to do some grave-robbing and take a capacitor from a broken PCB in my collection. Is there any reliable way to test the, uh, capacity of a capacitor? I've got a multimeter, but I don't know if it will do the trick.

[GonzoMPM-1]

Nope, they're the disc-shaped ceramic variety. I was thinking I might be able to do some grave-robbing and take a capacitor from a broken PCB in my collection. Is there any reliable way to test the, uh, capacity of a capacitor? I've got a multimeter, but I don't know if it will do the trick.

Can't "test" the size and rating of a capacitor without some higher level equipment.

But most electrolytic capacitors say what they are right on the side.

[ArugulaZ]

All right, I added those extra components! The output looks a little fuzzy, but it is composite output... I guess I shouldn't expect miracles.

[timmeh87]

Ceramic capacitors usually have their value written right on them.

for example, if it says "103", then it is 10nF.

the formula is simple, 103 = "10" * 10^"3" pico farads.

another example, "224", would be 220 nF.

http://wiki.xtronics.com/index.php/Capacitor_codes

If you can find something that is a few hundred nF, you could try it instead of an electrolytic capacitor. As electrolytic caps have high ESR, it is sometimes preferable to use ceramic or tantalum caps in high frequency applications.

The cap is just for DC blocking, the actual value is less important here.