Just make 100% shure, that it is rechargeable and 3.6volt. Not 3volt non-rechargeable.

Replace ALL the tantalun caps of the vga board, not only the exploded one, the other tantalun caps will fail eventually.

Use eletrolityc caps in place of the tantalum caps, they have similar characteristics and are more safe. I have did this in the past on a 386 motherboard that is working until now.

So wait, rechargeable 3.6V Lithium-Ion Coin batteries for cartridges and computers? Interesting.

All of my 386DX & 486 motherboards has a non chargeable external battery connector.
I'd be inclined to say that the one on this motherboard is non chargeable.
Easiest way to confirm is probably by testing it with a multimeter?

bjwil1991 wrote:

So wait, rechargeable 3.6V Lithium-Ion Coin batteries for cartridges and computers? Interesting.

Whoa! Don't use Li-Ion unless the charging circuit is meant for it (or you like pyrotechnics with your electronics).

Small world, I have the very same system - serial # 315183, only 4 higher than yours! And even more strange, as I pulled it out to try to get it going again I had the very same thing happen with the video card in almost the same place. Your C13 tantalum cap blew, my C14 cap blew - right next to it. Quite a little fireball and electronic smoke, but my motherboard was not damaged and I have another card in that same slot now.

I'm inclined to try to fix/replace the tantalum cap since the video cards are not easy to come by. I have questions that someone else here may be able to answer.

The caps are blue and say "10+" on the first line and either "16g", "16q" or "169" on the second, I can't tell but it looks like a small cursive "g" or "q". There are 10 total tantalum caps on the board.

1) Should all 10 caps be replaced? (Answered above by mut - replace them all.)

2) Can anyone here provide a suggestion to an appropriate capacitor to order? DigiKey for example has a TON of them:
https://www.digikey.com/products/en/capacitor … m-capacitors/59

I'm guessing the "10+" on my existing capacitors means "10 volt" and the + is just telling me which side of the capacitor is the positive lead. I then filter the DigiKey site on "active" part status, "through hole" mounting type, and "10V" at the DigiKey link narrows it down to 2,791 choices: https://bit.ly/35OT54i

Any ideas how to get this down to the 1 correct part to order? Oh and it would be really nice if said part was less likely to create a small fireball in my case. 😀

Thanks in advance.

I guess those blue caps are 10uF 16V, the '+' after the 10 indicates the positive lead.

Tantalum caps can usually (or always?) be replaced with electrolytic caps of the same values, right?

Electrolytics are cheaper and more widely available but obviously not as reliable and more prone to age related issues (drying out and/or leaking electrolyte) especially if run too close to the rated voltage.

OTOH electrolytic caps pop a lot less dramatically (and destructively) than tantalum ones do, so there's that, too, and I don't think they tend to fail in that mode unless heavily overloaded or run in reverse polarity.

Meanwhile, very old tantalum caps can apparently go bad in a manner that makes them flare up with a jet of flame or explode with a shower of sparks as if they're being overloaed or run in reverse polarity (but were originally installed correctly and functioned as such).

It seems like the latter happened on that Tseng ET4000 card and something similar happened to me with a Turbo XT board recently. Apolloboy mentioned it happening with an old keyboard or synthesizer he was working on.

I'm not sure what mode of failure that is, but maybe it's related to the insulating material becoming porous or cracked or having a small flaw in it that allows oxidation over long periods (including in storage) and leads to an internal short or some other internal damage that causes it to fail when powered on.

I haven't read into it either, but I'd assumed higher costs of tantalum combined with decreasing prices of electronic goods and increasingly high power demands of various computer systems led to the trend to favor electrolytic over tantalum caps. Meanwhile, it seems like more budget-oriented PC-compatible motherboards as well as low-cost oriented home computers and most home video game consoles had stuck to electrolytic capacitors from much earlier on or used such exclusively (along with small ceramic and film type capacitors).

PCChips 286 boards from around 1990 seem to use a lot more electrolytic caps (and few or no tantalums) than other typical PC motherboards from that period and much more like what you might find on Atari, Nintendo, or Sega console hardware. (or inside an Atari ST or Amiga 500)

kool kitty89 wrote on 2020-05-11, 02:23:

Tantalum caps can usually (or always?) be replaced with electrolytic caps of the same values, right?

No. The performance characteristics are too different to make a general recommendation like that. In particular, series inductance and leakage characteristics may require wide band ceramic caps or multiple capacitors (i.e. ceramic and poly) for equivalent performance. Of course, some applications didn't need the performance of a tant in the first place in which case a wet lytic or poly cap may be fine.

Murata does have application notes out concerning substituting MLCC for tant, but that's specifically for SMD components.

So if a Tantalum cap stops working or blows up, then only replace it with a new tantalum capacitor and nothing else, correct?

I replaced all the tantalums on my 286 board with electrolytics and everything works perfectly, no stability issues.

brostenen wrote on 2017-11-26, 22:46:

[...]

Keep in mind, that if the board charges the battery, then you can end up with an exploding battery if you use a regulair non rechargeable 3volt coincell. I have used one of these a number of times before. Works like a charm...

https://www.ebay.com/itm/Li-ion-Rechargeable- … F4AAOxyPH9RvsrS

Offtopic, but this link just made my day 😀

Been messing around with 3x NiMH AAA stuff but that always means cables to mess around with, and getting those big beasts charged and keeping them charged is a challenge. This is perfect.

Very helpful so far, thanks to each of you. I measured the existing capacitor and they are about 5.68mm high (just the blue part of it, from bottom to top of the capacitor on the board) and 3.25mm wide.

If I select the higher temperature (up to 125c) and size/dimension of 5.50mm (closest to the existing board) and in stock, I am down to only 12 options. https://bit.ly/2YZWE66

The only final meaningful difference appears to be tolerance - some are +-10 and some are +-20. Does it matter?

Here are two examples:
https://www.digikey.com/product-detail/en/kem … -3563-ND/818424
https://www.digikey.com/product-detail/en/kem … 9906-ND/3726207

bjwil1991 wrote on 2020-05-11, 07:25:

So if a Tantalum cap stops working or blows up, then only replace it with a new tantalum capacitor and nothing else, correct?

Tantalum for tantalum is the safest way, although other options may work in certain applications.

computerguy08 wrote on 2020-05-11, 07:43:

I replaced all the tantalums on my 286 board with electrolytics and everything works perfectly, no stability issues.

Congratulations. That is in no way an indication that electrolytics will work when replacing tantalums in all cases.

gdjacobs wrote on 2020-05-11, 17:39:

computerguy08 wrote on 2020-05-11, 07:43:

I replaced all the tantalums on my 286 board with electrolytics and everything works perfectly, no stability issues.

Congratulations. That is in no way an indication that electrolytics will work when replacing tantalums in all cases.

You are right, it isn't an indication that it will work in all cases. But I don't see the necesity of tantalums in common PC hardware. Most manufacturers pretty much abandoned tantalums since the 486 / Pentium era.

In fact, I have a few XT clones and none of them use tantalums at all. I would be curious, what exactly makes them "incompatible" with electrolytics in PC hardware?

computerguy08 wrote on 2020-05-11, 21:32:

You are right, it isn't an indication that it will work in all cases. But I don't see the necesity of tantalums in common PC hardware. Most manufacturers pretty much abandoned tantalums since the 486 / Pentium era.

In fact, I have a few XT clones and none of them use tantalums at all. I would be curious, what exactly makes them "incompatible" with electrolytics in PC hardware?

Apples and oranges. We know vintage hardware designed to work with tantalums for decoupling will work with tantalums. Boards may work with poly or ceramic caps as a substitute, but it's not a sure thing as it wasn't in the original design.

Electrolytic capacitors tend to have a narrow pass band compared to tants due to intrinsic series inductance. You can usually accomplish the same performance combining multiple caps which cover different ranges of the pass band, but the footprint required often makes it difficult.

If a variant of a card or board has factory original substitutions of tantalum and electrolytic capacitors, that might be an indication of compatibility ... or even that might be some manufacturer just fudging things a bit out of spec after finding it worked fine even if wasn't fully compliant on paper.

OTOH also bear in mind that lots of old hardware appears to work fine with degraded/dried up electrolytic capacitors and may indeed be no worse off running somewhat out of spec, but in other cases you might be doing gradual damage to things rather than just risking poorer stability. (though I've only specifically heard about the damage issue in context of capacitors in some vintage audio hardware and power supply circuitry)

So knowing a bit more about a specific circuit and whether the risk is functionality/stability or actual damage the hardware is significant.

https://www.youtube.com/watch?v=67M7fsbLUIU

That case is related to old paper in oil capacitors having the paper degrade and go acidic (non-acid-free wood pulp paper) in vacuum tube circuits, and specifically stuff caused by DC leakage.

Those are non-polar capacitors intended for passing AC and blocking DC, so pretty much the opposite context of electrolytic and tantalum capacitors used for coupling and filtering.

OTOH I've seen some dried out electrolytic filter caps in old linear power supplies (specifically approximately 1990 vintage Sega power bricks) that filter poorly and leak significantly more AC through than they should. (producing a lower nominal DC voltage as well as AC noise in the signal)
Albeit those may have actually leaked electrolyte and not simply dried out with age. (given the sticky texture around the cap and typical old electronic smell that usually goes along with very old electrolyte leakage + PCB + insulation material, it probably slowly leaked/wicked out, but wasn't bulged or corroded)

gdjacobs wrote on 2020-05-11, 05:49:

The performance characteristics are too different to make a general recommendation like that. In particular, series inductance and leakage characteristics may require wide band ceramic caps or multiple capacitors (i.e. ceramic and poly) for equivalent performance. Of course, some applications didn't need the performance of a tant in the first place in which case a wet lytic or poly cap may be fine.

While puzzling over capacitors used on the ISA slots of a 384/386 motherboard from around 1992 (in this case what I'm pretty sure are black plastic packaged, SMD tantalum capacitors, though aluminum poly caps come in similar packages).

Those are 10 uF capacitors (marked 106) and I think are used on both the 12 and -12V rails (I just had to remove one that failed short on the -12V rail). And there's no additional ceramic capacitors to complement them.

A couple other boards with through-hole tantalum caps and no complementary ceramics also appear to be 10 uF, but the Hedaka and PCChips 286 boards (D60 chipset, M205 and Hed 988) both use 47 uF wet electrolytics along with 104 marked ceramic caps (10nF) smattering of other value ceramics on the Hedaka board. (at least I think the 10nF ones are ceramic, they're little sky-blue suqare shaped things)

Actually, those 10nF blue ones are probably multilayer ceramics.

So it seems like significantly higher capacitance values are used for electrolytic capacitors in the same position as tantalum capacitors for power supply decoupling purposes. (maybe in part to account for drying out with age and heat, but probably also the need for wider tolerances in other areas, like ripple current tolerance, charge and discharge rate, etc)

Plus higher value electrolytic capacitors are fairly cheap and compact, so if the specific purpose works fine with extra capacitance values that's fine, too. (a higher margin for overvoltage might be wise)

I tend to see a lot of electrolytics that cut it close to the minimum voltage needed for a given circuit, like a lot of 16V ones for 12V lines and sometimes ones that actually undercut potential supply voltage ranges: there's some 10V power decoupling caps in the Sega Genesis console's I've opened in power supply filtering/decoupling circuits (prior to the pair of 7805s) that can sometimes be above 12V, I've seen 14 in some cases when open circuit, though that usually drops to around 9 or 10 volts with the system switched on. There's also some diodes in that portion of circuitry, which could account for some voltage drop but it still seems to cut it closer than typically advised.

OTOH the cap that failed on my board looks to be a 25V rated one, though there's also some 16V ones in similar positions on alongside other ISA slots.

Maraakate wrote on 2017-11-26, 20:09:

A friend of mine had some old hardware she was getting ready to pitch and one of them was a 486 tower. It had a Tseng ET4000 but had some custom soldering jumpers here and there. When I went to turn the machine on a tantalum cap popped on the ET4000. I removed the card, and the machine does attempt to boot. There is some series of beeps. I want to try another card in there and see if it's worth spending any more time on it. I don't want to spend huge bucks here and I have never played with a lot of stuff from the Pre-Pentium 1 era. Any recommendations on something cheap I can put in this machine to verify if it works properly and can upgrade later?

The motherboard is GA-486US (unsure of brand), Rev. 3. RAM is populated and a CPU is in there. I removed the controller cards and the SB Pro 2.0. Put the SB Pro 2.0 in a P1 machine and that does work fine! 😀.

From the model name (GA) I think it is a Gigabyte board. Not sure why I am writing this tho...

Random addition to motherboard naming, but older Biostar boards usually have an MB prefix. (somewhat confusing due to Fujitsu using the MB prefix on their ICs, and I don't think there's any relation there)

Also, I was mistaken about the 25V rated cap, it was one of the 16V ones run in parallel with that on the -12V line that was actually dead. (I managed to break the J-lead off the 25V one so I'll be replacing that too ... )