Recapped my Genesis - How important are capacitors?

[brentonius]

So, I decided to take the advice of the internet and replace all the caps in my model 2 Genesis. Although it went smoothly, something weird happened which I am wondering about:

 

It was my first time doing a full cap replacement, and I was very careful, and it all went well. I chose this Genesis 2 model because, honestly, it's the crappiest of my 3 Genesis consoles and wouldn't mind if I messed up...

 

So when I was replacing the caps, I would do a system check every 6 or so caps just to test it, to make sure I didn't screw up anything along the way. This way, I'd know if maybe the console didn't turn on or acted funny, I'd have messed up, and would only have to troubleshoot the last 6 capacitors. After turning on the Genesis after round 2 of cap replacements, all was fine. It worked, no problem. It was then that I suddenly noticed I had installed a capacitor backwards. The negative of the capacitor was where the positive should be. Quickly, I turned off the Genesis, took it back to the work area, and switched around the capacitor, bringing it back and checking it... and voila, still worked.

 

So this leads me to a couple of questions:

 

1) If I installed the capacitor wrong, why did the Genesis still function without a problem?

 

2) How important are capacitors? I think I understand what they do... they regulate voltage... but I think I am missing something.

 

3) Would I know if I had a capacitor installed wrong if I turn on the Genesis and it seems to run smoothly? Basically, does it running smoothly mean it will be fine for a long time to come?

 

When I went to the electronics store to buy the capacitors, I chatted with the owner of the shop. I asked him how important he thought it would be to change the capacitors and he said 'very' because they go bad after 10 or 20 years. For a 1990s console, he said it would definitely be a good idea because they are like batteries and go bad over time, not with usage, just over time... so yeah, definitely replace them he said.

 

But really, this is bugging me. Why didn't I see a problem when I had installed the capacitor wrong? I know it's wrong of me to think this, but this made me wonder if even replacing them is that big of a deal. I didn't notice any image or sound improvement. Also, I have a nagging feeling like if I installed one a little wrong (like, maybe too much or too little solder... and the capacitor may not be getting signal) then I won't know. I want this system to last. But now I don't know because maybe the machine still ran OK with a wrongly installed capacitor. So definitely confused.

 

Overall though, I am happy... the Genesis has been left on for 1 hour now and is just fine. I do think I installed all the capacitors correctly, it was my first time doing a full soldering job on an entire board mainly because I now felt confident enough to do so after doing a bunch of little solder jobs here and there. So yeah, victory. But with questions... and confusion...

 

But yeah, anyone out there (anyone with more knowledge about electronics) have some good knowledge about this?

Edited June 5, 2016 by brentonius

[icemanxp300]

My philosophy, If it isn't broken don't fix it. They don't make stuff like they use to.

[toiletunes]

Just guessing, but maybe it had little or no effect since there are so many?

When my genesis had cap troubles, it would play ok at first, but sound degraded gradually over ten or fifteen minutes of play- maybe a quick check isn't enough time to detect subtle damage?

I agree- if it ain't broke, don't fix it. There's probably a way to test if a cap has gone bad.

[jdgabbard]

Well, I will try to answer your questions and provide you with a little more info. And assume you're talking about electrolytic capacitors.

 

1) it is likely that one or two events occurred. One, that portion of the genesis hadn't powered up yet. Ie, it is something that is controlled by the system and is not just a cap on the power supply. Two, the capacitor simply didn't have enough time and current to fail. I've accidentally switched caps around when I'm prototyping, they usually get warm then the circuit starts acting erratically.

 

2) They are every important, and have many functions. But regulating voltages is not one of them. Depending on the type of capacitor and it's placement in the circuit it could be for stabilizing the power supply (when parts of a circuit turn on it can cause a sudden drop in voltage), act as a filter to block noise around integrated circuits, a filter to block DC and allow AC to pass, etc. Really, you could spend a long time studying capacitors and still learn more about how to use them. Heck, you can even use them as a analog delay.

 

3) No the electrolytic capacitor would shortly fail usually resulting in it exploding, leaking the the electrolyte over the circuit board (bad, causes corrosion), and possibly cause a short on the power supply causing the system to stop working.

 

As for caps going bad, it's because electrolytic and tantalum capacitors tend to go bad with ECs leaking electrolyte, and tantalum caps shorting out internally.

 

In either case, depending on the severity of the damage the system may or may not work.

[brento]

Some very useful information there thank you. Yes I also believed "if it ain't broke don't fix it" however if capacitors really do go bad, I think it's a good idea to replace them every 20 years or so... If you can. Anyways I left the Genesis on for a good two hours, and it ran very smoothly without a single issue. I think that since this was a success I will try fixing my other systems, starting with the Atari 2600 which probably needs a cap change badly.

[rayik]

You mat want to change the psu cap. I recently had a Genesis 1 that developed a humming sound. Recapped the Genesis and it still hummed. Turned out the cap in the power supply (psu) went bad leaking everywhere. Cleaned it up and replaced the cap, no more hum. I've been replacing the caps in all my old system psu as preventive maintane ce.

[Oge]

If I were to replace capacitors to a Genesis, I would use Low E.S.R. or Tantalum ones just to be sure that I will not downgrade the overall quality of the circuit. In case you are in doubt about one or more capacitors installed backwards, just practice with an old PC motherboard before recapping the Genesis again.

 

If the request is for a 10V@1000uF capacitor, use 15V@1000uF for a longer lifespan of the capacitor itself.

 

You do it once, and you're done.

[brentonius]

Interesting you mention that. All of my Genesises (Genesii?) make a slight humming sound. Even my SNES does. So I will look into doing a complete cap replacement and also the power supplies. Cheers!

[Oge]

The humming may be caused by weak ground on the cable side.

[brento]

Ok will look into that too.

 

I also noticed that game cartridges have capacitors too.

 

But question... Why do game carts have capacitors? And do you recommend changing those too? I guess the biggest fear is that one would leak onto your cart's board...

[ApolloBoy]

Why do game carts have capacitors? And do you recommend changing those too? I guess the biggest fear is that one would leak onto your cart's board...

It acts as a decoupling cap for the ROM chip; basically it smooths out the 5V coming into the ROM and hence provides clean voltage.

[brentonius]

Interesting.

 

So today I went into an electronics store again to buy more capacitors. Plan to replace all caps in my SNES, NES, and Genesis games.

 

Anyways, I asked the guy working there is he recommends the 105 C or 85 C caps. I mentioned that the ones I found in the carts have 85 C. He sort of laughed as said not to worry, they'll never get that hot, and even in the game console itself they'd never get that hot. Is he correct in that statement? Because I found 105 C capacitors inside the actual systems themselves. He seems to think it is no problem if I were to put the 85 C ones in the systems. Anyways, to be careful I am just using 105 C for all consoles, 85 C for the carts. But I was a bit curious as to how hot they do get. Anyone know?

 

Sorry for asking so many questions about capacitors, but I am really curious!

Edited June 11, 2016 by brentonius

[Osgeld]

your making it way harder than it has to be, its simple dont buy crap wang dang dung from ebay 99 cents free shipping for a bag of 1000 and it will probally last another 30+ years

Edited June 12, 2016 by Osgeld

[brentonius]

All of the capacitors I bought are Rubycons, which the man at the electronics store (and a Google search) mentioned were the best of the best.

[Osgeld]

i mean 85c is 185F almost all your silicon will fail well before hitting those operating temperatures, and rubycons are ok, dunno if I would call them the best of the best, I wouldnt call any of them the best of the best, they are average of the above average, but not crap, and that's the important part

[brento]

Cool. This is great stuff I'm learning here...

[atarilovesyou]

If systems need recapping after 20 years, nobody told my many NES systems that.

 

I realize it's a factor, but in my experience it's not an issue. Doing some work on my 'parts' Genesis board lead me to one decision: leave that sucker alone. The solder points are so small that even removing the simplest of things is difficult...I found out removing the LED part last week, took forever and I was glad when it was done (and worked).

 

Also, it's tough to say if your problems are capacitor related. I often feel that the only people to gain are the ebay and other sellers with their 'cap kits'. Capacitors are generally cheap as anything and it doesn't take much to put together a pack of them for any given system.

 

Troubleshooting an old board to find out what's wrong with it is best left to techs. I certainly don't think I'd do it myself, at least not with a lot of practice on junker systems.

[Oge]

Low E.S.R. makes a difference, temperature rating - as already pointed out by Osgeld - not.

[segacdnerd]

What sort of difference does it make to use low E.S.R capacitors over the standard ones?

I was reading about E.S.R due to your comment, the wiki page, they list standard aluminum as 7-30ohms and low ESR aluminum as 1-5. That's a lot less resistance!

But then you have low ESR tantalum at 0.2-1, solid aluminum at 0.2-0.5, Sanyo OS-CON at 0.04-0.07, and then you press on down to <0.015 with stacked-foil film and ceramic.

 

What would you say is the ideal option? If resistance is bad, lower is better yes?

Does that mean if I were to replace the capacitors in my console, say a Genesis, I should ideally use stacked-foil film or ceramic?

 

I have no idea the price of any of these and I can assume that some of the options simply aren't a good investment due to prohibitive costs.

Do you by any chance know what some average prices for an identical capacitor utilizing the varying electrolytes?

 

Sorry for asking so many questions, I know very little about such things but they interest me quite a bit!

[SwampFox56]

I agree with the above. Recapping a system should only be done by those who don't care about ruining a Genesis, OR should be done by people who know how to do recaps (aka... me ) I've seen so many botched mod jobs that I've had to cleanup and repair. Basically, if you can't solder - don't attempt it.

If you do know how to solder, but do not own the proper desoldering equipment - then you should also not attempt to recap a Genesis.

[Oge]

Recapping a Sega Genesis is IMO a pretty simple task.

 

@segacdnerd: You can use tantalum if you do not care spending a bit more. You have to be very careful about the fact that tantalum do not like at all functioning with inverted polarity.

 

Most of the capacitors are 16V@10uF so the budget will be good even with the highest quality capacitors.

Edited June 21, 2016 by Oge

[segacdnerd]

@Oge - What sort of difference does it make to use the low ESR capacitors? Do they just last longer? I know the solid ones don't pop and ooze like liquid, which is nice.

[Oge]

Ideally, a low E.S.R. capacitor has less current leakage. In other words, less ripple. And the less the ripple - ideally - the more the lifespan of the ICs.

 

At each startup of the machine a set of low quality capacitors (or very old ones) may cause a spike/bump which stresses the machine.

 

Internal resistance of the capacitor increases over time and while the machine is functioning due to heat. So, 105° Low E.S.R. is ideally better. Sanyo capacitors (green colour) are very good.

 

The more a capacitor is used/old, the more the resistance. And the budget for recapping a console is very low, why go cheap?

[Osgeld]

while I do not disagree, and let that point be known I usually recap with 105c 10,000 hour panasonic blacks cause it only cost a little bit more, but lets look at the big picture ... caps in a system were not chosen for last forever they were chosen to last the system's lifetime and have done that and exceeded that for decades, while being as cheap as possible the #1 factor in mass production. Replacing caps with some decent brands, even low grade ones will last another 30+ years

 

so why go cheap, but you dont necessarily need the super delux versions either, considering a system full of them can net 10x the cost, getting close to the entire value of the system itself at current market

Edited June 28, 2016 by Osgeld