Sorry, this isn't exactly related to 6502 but hopefully it will be somewhat useful.

I brought out my Amiga 2000 last night and discovered one of the capacitors leaked. I'm going to replace it with a high quality one (suggestions appreciated).

My question is on the temperature ratings. Normally my machines are stored in my basement where the year-round temperature is somewhat comfortable. But I may start storing some of them in my storage building (water-tight but not climate controlled). In the South, it gets brutal hot most of the year. So, should I try and find capacitors that are rated for higher temps? Does it even make a difference if the cap will not be used and only stored in high temps?

Thanks for any suggestions.

** EDIT **

Correction, I haven't looked in great detail yet...only snapped a few pictures before I went to bed. But that might actually be a battery shown below. But, my question still stands.

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Cat; the other white meat.

That's a NiCad battery to keep the CMOS set-up memory alive.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Ah, you posted that just before I corrected myself.

Yeah, you're right. I didn't really look closely after I took the picture.

However, I'm still going to re-cap that board so my original question still stands.

Thanks.

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Cat; the other white meat.

Mouser and Digi-Key have the data sheets on the various ones online, so you can get all the details of ones you're considering. I've been involved with high-end intercoms for private aircraft since 1992. Many of our customers' aircraft sit parked on the tarmacs most of the time, and can get very hot (like a parked car), yet there has only been one size (6x11mm) and value (220uF) and type (aluminum electrolytic) of capacitors that have ever shown a problem with lifetime, going south starting at about 15 years of age. No other electrolytic capacitor has had any problem; so I assume there was something wrong with that lot. We have had infant mortalities on monolithic ceramic capacitors though. We've never had an OS-CON capacitor failure. (That's a type, organic semiconductor, not a brand, and it's even far better than tantalum for low impedance for switching power supplies. It's made by two or three different manufacturers.)

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Great. Thanks for the suggestion. I did a little more digging and discovered that battery is not needed for the Amiga. At least, not for me because I really don't care (at the moment) if my Amiga knows the time of day.

So I may just remove it (and clean up the board) and try using it for a while. When I get around to adding a new battery, I thought about using long jumper wires from the board to a more modern battery. And, put the battery in some type of enclosure so that if it leaks, the corrosion would be contained.

I think the Amiga even charges that battery. I discovered there are replacement circuits that put a modern coin battery there but have circuitry to prevent charging.

Anyway, I'm still trying to find the schematics.

But for the other caps, I will slowly start replacing them with higher quality ones.

Thanks again.

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Cat; the other white meat.

There is a schematic: http://www.amigawiki.de/dnl/schematics/A2000_R6.pdf

The problem with the batteries on Amiga boards is, that the corrosive liquid will corrode traces and therefore your Amiga will probably malfunction.
It needs a proper rework or you'll have issues forever. Best thing would be to relate to an Amiga forum where experts can help you.

The capacitors on the board are not known to be a problem and you shouldn't change them before your board is running. Otherwise you might include more faults than you fixed in the first place

It does look like the green plague has spread at least a couple of inches from the battery itself.

There's also a missing/broken capacitor just next to C261.

I have some bits and pieces which I've been careless enough to store with batteries in - but really I should know better than that.

@crassbe

My version is 4.1. The schematics you provided might be close enough. But I just don't know.
I've struggled with the whole "to recap or not recap". Some say always recap on old machines. Others say only recap after you have proven there is a problem (proper ESR readings). Unfortunately, I don't have an ESR meter so my testing is limited.

@BigEd
Yes, the green certainly has spread a little. That pic you see is before I cleaned some of it. It looked like the green was coming off. The CPU (68K) is socketed and I have a spare one. It has some green on the pins but I might be able to clean it off.

Overall, it actually doesn't look super bad compared to others I've seen. I'm almost thinking it recently started leaking. Even though I haven't powered it up in over 10 years.

Broken cap near C261? Hmmm. I haven't noticed that. I will look closer for sure at that when I get home.

**EDIT**

You're right! I see that now. I had to zoom into the pic.

I will look over the entire board tonight. But, it is a LARGE board.

I will say this...I only powered it on a few times when I bought it over 10 years ago. Then it went straight to storage. Other than plugging in a memory card, I haven't touched it. I don't know what the previous owner did to it. But it did work at one time. How well it worked is a mystery since I didn't really stress test it. But I will.

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Cat; the other white meat.

I think with the electrolytics, you look at them to see if they are bulging (or leaking)

With the tantalums, I think possibly you stand by to replace them all, because they fail suddenly.

It seems that heat decreases the life of electrolytics:
http://www.electrojumble.org/reforming.htm

Also, with electrolytic's, I believe the electrolyte can dry up...reducing the capacitance. So, it may not be leaking...or even bulging....but the capacitance is affected. Which brings it closer to a sudden failure. And, you cannot know that without a proper ESR reading.

I might be totally off base there...but that's what I've understood.

BTW, did I mention how large that board is? It has more surface area (2D) than my 15" laptop. Seriously.

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Cat; the other white meat.

Ed's video link on capacitor technology at viewtopic.php?f=1&t=4188 addresses the matter of the aging of electrolytic capacitors, and restoring them. (It addresses a lot of other things about capacitors too.)

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

You really want to focus on the battery first! There are no tantalums on the Amiga 2000 PCB. Just ceramics and electrolytics.

@Garth

Thanks for the video reference. I will be sure to watch that.

@crassbe

That's good to hear. Recapping the A2000 should be pretty easy but tedious. There are a LOT of them on that board.

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Cat; the other white meat.

The capacitor question is simpler than you might suppose. Yes, dried electrolyte can reduce capacitance but that's not likely to cause a sudden failure. As for ESR, if you have an actual symptom -- ie, the machine is misbehaving -- then one way to test ESR is to temporarily install a new cap in parallel with the original. If the symptom disappears then you know. Alternatively, skilled use of an oscilloscope will give an indication as to whether the cap is doing its job. (These remarks apply also apply to reduced capacitance too, not just to excessive ESR).

Good advice, IMO!

-- Jeff

PS:In common usage, an "electrolytic" cap is often understood to mean an aluminum type electrolytic. But this is misleading, as tantalum caps are actually electrolytic, too.
https://en.wikipedia.org/wiki/Tantalum_capacitor

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Please remove that battery and neutralise the leaked base before it continues to do damage, if you haven't already.

Fix the battery damage before pondering any other work. Capacitors will not keep it from working at this point. Battery damage is not always as straightforward to repair as you might think, and you don't want to spend a bunch of time and money on a board that you eventually determine isn't within your budget to repair.

Search Amazon (or wherever) for 3.6V cordless phone batteries with pigtail leads. You can get NiCd or NiMH. Or if you're like me, just replace it with the original style battery and plan to change it in 10 years.

I've repaired several battery leaked Amigas lately. It's not what I'd call fun. I've got a 486-based AT clone to do next. I might not bother.

I think you're very far away, else I'd offer to fix the board for you.