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Glitchy video / random characters


rbairos

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Hello a friend just acquired a colecovision and 2 carts (Smurf and Cabbage Patch Kids).
Cabbage patch rarely starts up, and Smurf starts up with several artefacts half the time.

Any advice how to start diagnosing?

From the little I know, it may be a DRAM issue?
In which case, I should look for dry solder joints and/or consider a DRAM update kit which foregoes the multiple voltages?

Thanks for any info,

Rob.

 

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The cart contacts and the power switch are the most likely culprits.  May I suggest properly servicing the power switch if you have the tools.  Just spraying deoxit in there does nothing to (i) remove any old grease and (ii) provide lubrication for future use.  Following the attached instructions (not mine) should put your power switch back into almost as-new condition.

power_switch.pdf

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2 hours ago, dsullo said:

My colecovision seems to be doing the same thing.  I am really not technical so maybe I will first try cleaning the cartridge contacts with some electrical contact cleaner.  If that does not work is there anyone on the boards who services the system? 

To help find potential repair people, could you narrow down your location?  But really, cleaning the contacts in both the cartridge slot and the switch is the first line of troubleshooting.

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Ok fair enough.  I live in New Jersey USA.  I will use a toothbrush to clean the contacts of the cartridge port and see if I can figure out how to clean the power switch. Is my only guide the PDF or is there any tutorial videos ? I could not find any on YouTube? 

I will post results in the next few days

 

dustin 

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1 hour ago, dsullo said:

Ok fair enough.  I live in New Jersey USA.  I will use a toothbrush to clean the contacts of the cartridge port and see if I can figure out how to clean the power switch. Is my only guide the PDF or is there any tutorial videos ? I could not find any on YouTube? 

I will post results in the next few days

A toothbrush won't clean the cart port contacts.  You need to use something that will wipe clean the surface of the contacts.  Personally, I use plain card business cards that I spray with isopropyl alchohol or contact cleaner.  The cards need to be stacked so that they are as thick as a cart PCB edge.  Then push the card into the cart slot and remove, repeat several times.  Then repeat again with new card and more alchohol.

 

I've never seen a YouTube video for the power switch repair.  The pdf I posted gives good instructions and is what I follow when doing my power switches.

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Wow I can’t believe it but I opened the colecovision and used electronic  contact cleaner on the cart slot and power switch and to my amazement it actually seems to have fixed the issue.  The electronic contact cleaner seems much more effective than alcohol. 

See the nice clean image.  

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Alright here's the update:

Spoiler:  it works again.

What we did:

1. First we cleaned all the cartridge edges, and the connector.
We used white erases, deoxit and isopropyl alcohol.

Unfortunately same problems remained.

2. We then were able to take the case apart (just 8 screws on the bottom, without disturbing the metal front plate), though this took some careful fiddling.
We were also able to remove the shielding which luckily was just soldered on one spot, removing some easily accessible screws.

This gave access to the switch, which we just sprayed with deoxit without removing its case.
We also inspected for bad solder joints, and gave the board a gentle cleaning with a toothbrush and isopropyl alcohol.
Unfortunately same problems still remained.

3. Finally we desoldered the power switch main upper casing from the board. (Two large solder points)
This revealed six contact points, 2 of which were black, the rest yellow.
This cleaned up easily to a shiny silver color.

The problem still remained, but after a couple of switch cycles, all was finally good consistently.

So our success rate went from about 10% to 100%.

Thanks for all the tips!

Rob.



 

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