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Coco 2 capacitor

fdiskitup

fdiskitup

Experienced Member
Joined
Mar 2, 2022
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Location
Chicagoland, USA
I have working coco 2 that I recently aquired. Model 26-3134 made in Korea.
I upgraded the ram to 64kb and stole an Enhanced Color basic rom from a non working board.

Anyway to get to the question, does this capacitor look like its leaked or did tandy use glue?
Its a 4700uF 16V. Part of the power circuit.
The system is working so should I mess with it?

IMG_4013.jpeg
 
Definitely something going on there. Solder on adjacent components looks suspicious too. Also the diode behind the capacitor looks as if it's been getting way too hot.... could be a problem itself or an indication the capacitor is going bad.
 
Hard to tell - the stuff towards the "+" marking looks like glue, the remaining visible stuff looks like something has escaped from the capacitor.
I'm wondering if the capacitor was glued which held the capacitor down and stopped stuff escaping towards the camera, and meanwhile stuff escaped from the weaker parts (probably where the glue either wasn't applied or applied more sparingly.

Can you post a picture showing the opposite side of the capacitor?

Having said that, you are probably going to end up having to desolder/replace the capacitor anyway, so you might as well crack on.
 
If it was cap juice I would imagine we'd see alot more corrosion. I think its the typical hydroscopic glue used to hold components down. The solder looks old, but its all still shiny. I really dont think the cap is leaking from this photo. I think its dirt/debris.
 
Isnt there a paper insert/separator somewhere near the psu components? I know the model 1 has one one the transformer board. If the system was exposed to water the paper could have turned to pulp and thats what were seeing. Cellulose fibers.
 
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Hmm, is the test for cap juice to rub with a dry q tip ? putting vinegar on it to see if it bubbles is for nicads, I'm not sure what electrolyte is used in caps ? the web is a little vague about exact materials .... ethylene glycol and boric acid, also called “borax” electrolytes. Antifreeze and washing powder ?

I'm thinking to desolder it - I have a Cap meter, not sure if it will go all the way to 4700uF
 
...put a soldering iron to any area in that mess with solder exposed( L1 for example). IF the burning solder smells VERY FISHY its cap juice.. if it just smells like burning its not. There is a VERY distinctive smell to burning electrolytic leakage.
 
Thankfully not mices this time. Just mold and cigarettes,
And the theres this other one that needs attention…
 

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fdiskitup said:
Your board looks in much better shape - look how shiny that rf tuner box is.
Different diodes too. Thanks for confirming. It looks like the glue may be the hydgroscopic type that breaks down if stored in a damp shed?
Now the dilema is should I mess with it.
Click to expand...
Mess with it? You should fix it. Start by putting it through the dishwasher.,.. then yours will be shiny too.

Note.. Dont put the keyboard through the dishwasher.
 
its probably good practice to put 4k7 on both if we're tying them to Vcc ? and i think there is already a 0.1uF decoupling cap for the 24 socket.
 
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