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Colecovision repair?


iridude

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I haven't tried anything yet. The power switch I looked at and for sure someone tried to fix this. However, none of those  two sliding parts those small things that go into switch. Can I use aluminum foil or something else to see if I get something at least? Or not a good idea? I for sure need a new power switch which I ordered. In meantime just trying to see if I can get anything to work.

Edited by iridude
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Ok it seems I have power now what should I check I have what it says on my tv no signal.  I am guessing rf but not sure what to check to see if I get a voltage.

 

I went to colleco tech manual and did following:

 

Check voltage on board and power supply all looks good there

 

U9:36 nothing with logic probe. However, I have no cartridge in not sure if that makes difference here or not.

 

U9:17 - 24 does something on logic probe assuming good

 

U9:33 shows +5v volts to be exact 4.96

 

U9:40 seems good

 

U9:34 high on logic probe

 

U7:13 high on logic probe

 

It says now check U7 and U1 does that mean those chips maybe suspect and should be replaced? I am confused on this. Thanks

 

Edited by iridude
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2 hours ago, iridude said:

Ok it seems I have power now what should I check I have what it says on my tv no signal.  I am guessing rf but not sure what to check to see if I get a voltage.

 

I went to colleco tech manual and did following:

 

Check voltage on board and power supply all looks good there

 

U9:36 nothing with logic probe. However, I have no cartridge in not sure if that makes difference here or not.

They have to mean oscilloscope for that pin.  That's an analog output.  It's the B/W part of the composite signal.

 

Quote

U9:17 - 24 does something on logic probe assuming good

That means the rest of the system is doing stuff.  Not necessarily the right stuff, but it's doing stuff.

 

Quote

It says now check U7 and U1 does that mean those chips maybe suspect and should be replaced? I am confused on this. Thanks

When the system doesn't work, any chip is suspect :)

For U7, make sure pin 12 is low and pin 10 is high.  Make sure pin 6 is low.  Pin 4 should be high/low pulsing, but mostly high.  Pin 2 should be pulsing.  Pin 8 only pulses when you use the roller on a SAC or the trackball in trackball mode.

 

U1 is the CPU.  There are no simple checks for that.  But if the address and data lines are doing their thing, then it may be okay.

Edited by ChildOfCv
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I checked U7 pin 12 is low; 10 is high and pin 6 is low; pin 4 is pulsing; pin 2 is pulsing. I guess this looks ok.

 

What else should I check? I am getting no input signal on my tv. thanks

 

I am guessing rf modulator. Not sure how to check this though

Edited by iridude
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I checked u10 through u 17 and read somewhere that pin 14 of the ram should be pulsing.

 

my probe shows this. All the ram chips show this. Is it possible all the ram is bad? Could this cause a no signal issue though? 

 

 

128D2104-D2FC-42F3-9A7C-8477774AEAA1.jpeg

Edited by iridude
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3 hours ago, iridude said:

I checked u10 through u 17 and read somewhere that pin 14 of the ram should be pulsing.

 

my probe shows this. All the ram chips show this. Is it possible all the ram is bad? Could this cause a no signal issue though? 

No, lack of signal is different.  The video chip still creates a raster image even if the RAM is bad.  If you have a composite mod handy, connect it to pin 36 of the video chip and see if it creates a B/W image on the TV in AV mode.

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I don’t have that mod but I was thinking of buying the one at console5 with Trss are all the av mods the same? I heard some won’t work the Atari’s expansion module. Example I would connect red wire to pin 36 and ground to a ground and should get a b/w image. 

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10 hours ago, iridude said:

I don’t have that mod but I was thinking of buying the one at console5 with Trss are all the av mods the same? I heard some won’t work the Atari’s expansion module. Example I would connect red wire to pin 36 and ground to a ground and should get a b/w image. 

Composite mods would work.  I would suggest this one:

https://console5.com/store/colecovision-composite-av-video-mod-kit-ntsc-consoles-coleco-vision.html

It has the least impact on the rest of the system.

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9 hours ago, iridude said:

I tried something so the switch for channel if I put it in middle I get picture but has sound but it has lot of noise. Only getting signal on channel 4 this switch not supposed to be in middle correct? At least getting signal now

 

It could be tuning.  Around the center of one side of the board there should be a hole in the board.  That hole gives access to the channel tuning adjuster.  There should be a ferrite slug with a hex head there.  It should not be broken, crumbled, etc.  If it is, then you probably won't be able to tune your RF output properly.

 

But you can still install the composite mod to make all of that irrelevant.

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