Vintage/retro motherboards recapping

keke

Weaksauce
Joined
Dec 27, 2020
Messages
67
Just adding a few thoughts on this topic.

The issue: I have (like many others) a bunch of moherboards/systems from different years - some looking good, some with leaking capacitors, or even older mobos with tantalum capacitors. As I want to keep these motherboard functional for next 10-20 years (at least), recapping is a must (I assume).

The question: are there any rules for vintage/retro motherboards for recapping? Like, what is a must for recapping if older than X years? Similar to vintage tube radios from 30s and 40s, where recapping is a must :)

- some Sinclair Spectrum ones, and Commodore C64C to start with
- say for early IBM PCs - IBM XT 5150 and 5160 as examples - tantalum capacitors tend to cause fireworks because of age...
- for standard 286 and 386 motherboards?
- for 486 motherboards?
- early 93-94 ones - including first Pentium Socket 4?
- motherboard between 1995 to 2000 - covering Pentium II / III and Athlon - Slot 1 and 2, Slot A
- guess for motherboards after 2000 recapping is not a must - unless known to be affected by a bad capacitors batch/period (2009-2010 perios was mentioned earlier).
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
1,708
If we're talking about machines from the 1980s to the early 1990s, then capacitors are the least of your concern on most PC hardware, except in specific places like the power supply. More immediate threats are leaking NiCD or Lithium CMOS batteries and death adapters. The former is self explanatory, no battery lasts forever and computers from the 80s to the mid 90s used NiCD or large Lithium batteries that leak or explode and trash whatever they seep on to. The latter is insidious because most people trust power supplies a bit too much and expect them to always be good. Killer power supplies are a leading cause of death of old computers.

The linear wall warts and bricks that some computers used, like Commodore 64/128s are subject to drift upwards in voltage over time, and can be out of spec by orders of magnitude their original ratings. What causes this is damage to the internal core of the linear transformers that happens over time. Three factors being heat, vibration and pressure all work together to cause the microns thick varnish on the copper windings in the core to migrate into gaps between the windings, which shorts them together. The more windings that short, the more the voltage changes, usually going higher. Past a certain point, the voltage is out of spec and will cause damage. Too far out of spec and stuff will start blowing up. I've had to throw out most of my old linear wall warts because of this problem, but I keep my two Sega Genesis wall warts for completeness but never use them for obvious reasons. The original voltage rating of them was 9 or 10v and they now put out 17-24v the last time I checked a few years ago.

As for capacitors, shotgun changing them should be on a case by case basis. If you have a board with ceramic or tantalum capacitors and the board works fine, I would leave it well enough alone. I would however get some protection for the board like this really cool project:

https://github.com/x86fr/ATX2AT-Smart-Converter

Shorting tantalums can pull enough current to blow traces. But you're really no safer with new tantalums because new tantalums can fail as well. What actually causes them to fail is usually not age, but being insulted. Unlike electrolytics or film capacitors, tantalums can't "self heal" after an insult event and usually just short out or explode. The insult that makes them fail is usually voltages exceeding their rating, like voltage spikes. But it can also be induced by shock or thermal damage.

If you have a motherboard with electrolytics, I would only change them if it is known to have problems, you can see or measure problems with the capacitors, or if it is in unknown condition from buying it from someone else. Most computers that used radial or axial electrolytics from the late 70s to the early 90s can be fine if the machine was stored in proper conditions. However if the machine was stored in an attic, basement or garage where subject to all matters of temperature variations, you should probably recap it.

Two exceptions would be power supplies and Apple computers. Power supplies obviously because they're subject to a lot of wear and tear, as well as having problems with things like RIFA capacitors. Apple computers, well because Steve Jobs was an idiot. His poor design decisions that he forced down the pipe like not having vents or even a cooling fan doomed many Apple machines to failure. The Apple III was like this, as well as almost the entire original compact Mac line. The Compact Mac line didn't get a fan until the Mac SE, and even then it was inadequate. The whole compact line had problems due to severe overheating, including cooking all of the capacitors as well as other things. Another problem in the late 80s was their love of the then new SMD capacitor. These have all failed in every Apple machine to have them and must be replaced because they've all started leaking by 10 years ago.

Capacitors from the late 90s onwards were problematic, and it got especially bad in the early 2000s with the capacitor plague that still goes on to this day, but the worst of it had tapered off some by 2010-2012. Basically everything that had a electrolytic capacitor on it would be affected, but motherboards and power supplies are the worst. Antec supplies in particular used probably the worst garbage in their Basiq, Smartpower and Truepower lines. I've recapped dozens of those.
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
1,708
Yes, I came across this power source adapter, looking to get one when made available :)

It was a kickstarter project, I don't think the guy that made it has any intention of doing production runs of it. He made it an open source project so you can just send the PCB design off to a Chinese board fab and put one together.
 
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