[Q] Recapping consoles with solid polymer caps?

Is this a thing? The only problems I could think of arising is that higher voltage large caps like 2200uF or 1000uF >= 25v variants are not available, so those would still need to be electrolytic, and the higher price.

Would this make consoles more reliable, or have any benefit over replacing them with good quality Panasonic/Nichicon/Rubycon electrolytics?

 

different properties, I have no idea if there is going to be any noticeable difference but honestly, those caps where chosen by the designers for a reason.

 

This is actually an interesting question. I think the only potential benefit is longevity. Solid polymer will probably last longer than electrolytics. I can't imagine the console working any "better" with higher quality caps. Maybe if we're getting super nit picky about video quality, better caps on the video lines might change the output ever so slightly.

Do you have any particular console in mind when posing this question?

I generally go along with such a statement...but I feel the main reason electrolytics were (are?) used is because they provide the needed capacitance for the lowest price. I read this question to ask, "if I throw money at higher quality components (al la the philosophy behind the Analogue NT), will it work any better?".

 

By running better, I just mean lasting longer. No particular console comes to mind.

 

how long has any console that you think of lasted? Not including ones with known bad batches of caps..

 

If you are replacing caps in a portable game system, then go electrolytic or any other substrate with low DC leakage, not polymer. Polymer really shines in mains powered devices where leakage is not a concern, and high amounts of current is demanded.

Yes and no, depends on the application, this can get a slight bit technical.

Polymer caps will not dry out over time, they can last thousands to tens of thousands of hours under strenuous heat stress (+100 C), they are more thermally reliable over electrolytic.

The biggest argument in favor of polymer caps is their characteristic frequency response curves, they tend to have lower ESR (and ESL in certain designs), as well as higher spec'd ripple current. The lower ESR improves power filtering by removing unwanted AC and switching noise in a DC power rail. The lower ESR also helps reduce voltage drops under heavy system load or during times of transience.

In some applcations, i.e. certain voltage regulators, require an output capacitor with an ESR above or below a certain range - datasheet would specify. Having a cap with ESR too low for the regulator will introduce instability and noise to the circuit.

It should be mentioned that some electrolytic caps can have frequency response characteristics quite close to polymer caps - a bit of product investigation is needed to find them. Polymer caps are significantly more expensive, they are usually implemented on more expensive electronic devices.

 

My Commodore 64 is still going strong, but I'm going to replace the caps soon.

My Super Famicom on the other hand, has a dry cap or something that is causing video interference.

That's really good to know.

 

I have replaced electrolytic caps with polymer caps in a few consoles along with their power supplies.

C67 on the SNES acts as a reservoir capacitor for the console, supporting a ~10V input for the 7805 regulator. I had a minor short circuit accident and decided to replace the original much physically bulkier 1000uF C67 with a much smaller Polymer United Chemi-Con cap (APSG160ELL102MJB5S). My oscilloscope showed the 10V line was much smoother and more DC-like, this cap did an excellent job removing lower frequency noise (sub 1 MHz range).

Polymer caps can operate very well at close to their max rated voltage with no issues due to several of their characteristics. Manufacturers provide this information - I strive for no more than 75 to 80% of the rated voltages in my projects.

 

Quick unrelated question: Everything I've learned about cap replacement is to never go under the original voltage rating. The original for the SHVC-CPU-01 (what I have) is 25v, but I see that you replaced yours with a 16v one. Since the input to the SNES is only 7-12v (10v in my case), is that a guarantee that the cap will never be charged >12v?

Also I already got new electrolytics for my SFC, so maybe I'll try it out with my Genesis or PS1, and just use electrolytics for the voltage regulator input/output. But could you not get polymer caps with a higher ESR rating for voltage regulators?

 

I've measured the voltage on that cap with the original PSU and it never got above 14v.

When there is no load on an unregulated psu, the voltage is higher. That's why it can reach 14v from a 9v PSU.

 

That is a good guideline/rule to follow when replacing caps, but a capacitor has several other properties needed to be taken into account in a circuit that may be more important, not just voltage rating alone. There is quite a bit of science in capacitors, even those of different substrates – I would not go on Mouser or DigiKey and start picking and placing random electrolytic or polymer caps in circuits without understanding what type of circuit they would fit best.

Nintendo de-rated the C67 cap, and decided to use a 25V cap for their own reasons regarding safety, failure, and longevity under stress.

I came up with my own derating scheme. I took a closer look at the circuits before and after C67, and I found a polymer cap that would fit the scheme. I am feeding a 10V to 13.8V current into the cap, it is rated for 16V. This is not an issue so much with polymer caps as with electrolytic, the more headroom, the more peace of mind. The cap I used has a datasheet describing its characteristics, I probably won’t be running this lonely cap at 16V, at 105 C, for 20,000 hours as the datasheet rates them. If I am concerned with the voltage, I could construct my own power source that feeds a regulated 7V to 12V current - the 7805 would certainly be operating at a cooler temperature.

It is best to understand how the circuit is working, and select a cap accordingly. Polymer caps and ceramics caps have very low ESR with respect to their capacitance and may be suited for some linear/switching regulators, but not others. A regulator’s datasheet oftentimes describes this with an output capacitance vs ESR graph. Two 100 uF caps with an ESR of 100mOhms at 100 KHz in parallel equate to a combined 200uF capacitance and combined 50mOhms ESR at 100 KHz – some regulators may or may not like this. Too little capacitance and or ESR can cause regulation issues, too much capacitance and or ESR can cause regulation issues – too much capacitance can also cause destruction of other components.

 

So the gist is use electrolytics for high ESR needs, and use polymers for low ESR needs?

So Nintendo could have used a 16v rated cap without any problems?

 

Not exactly, I would recommend this link here. Google is everyone's friend and can help you learn more about caps and their proper implementation.

Yes, a 16V electrolytic cap would certainly work, being electrolytic I would derate it. Again, read the datasheets and the other specs of the cap. Not just voltage.

 

Well I replaced it with a 35v electrolytic because that's what I had. I'm no electrical engineer, so I'll read that link you linked.