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Restoring a Sun SPARCstation IPX Part 1: PSU and NVRAM

Andrew Back
Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.


August 4, 2020 07:10

You will be interested to know that a large portion of the photomasks, used to make integrated circuits, manufactured today are built with equipment still using Sun Sparc 2s, 20s and Ultrasparcs. It's a testament to the quality of Sun computers. In fact, a lot of the equipment in mask shops and wafer fabs still run DOS or Win NT. The replacements, if there are any, are too expensive for the mature market.

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August 4, 2020 16:37

@deaddog Interesting indeed, thanks. I guess this is much the same as how PDP-11 computers often ended up in process control and remained there for many years, quietly and reliably doing their job. I'm also told that Transputers got used a lot in MRI machines and systems based on these were maintained way beyond when people stopped using them in new designs. All these architectures seem to find one or more particular niches and committed advocates who appreciate what they bring to that area.

July 13, 2020 08:01

You can set your sparcstation to boot disk via command at OBP:
setenv boot-device disk

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July 14, 2020 07:36

@Topkek456 Yes, indeed. Planning to take a look at OBP a little more in the next post in the series. It's pretty cool and the OpenBoot reference manual is a nice read.

July 2, 2020 14:42

@Boss and Andrew, here is a short pdf that helps predict reasonable life expectations for electrolytic caps:

From that source,
Aluminum electrolytic capacitors slowly degrade over time and once the capacitor has degraded beyond a specified amount, the capacitor is considered to have failed. Most capacitors are considered a failure when the capacitance has changed by 20 to 25% of its initial value. Aluminum electrolytic Capacitors load life’s ratings are generally expressed between 1000 and 10000 hours at their rated voltage, maximum temperature rating and with maximum ripple current applied to the capacitor. This means that the capacitance of the capacitor will not change by more than the amount indicated under the load life rating when the capacitor is operated at the stated conditions. Although the life expectancies appear be a short amount of time the following can increase them. When the capacitor is operated at temperatures other than the maximum rated temperature for the capacitor the expected life of the capacitor will increase. The rate of increase in operating life is for the life to double for every 10°C decrease in temperature (Arrhenius’s law).

The paper points out the life is also affected by applied voltage vs rated voltage, and by temperature rise due to ripple current, and provides formulas.

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July 6, 2020 08:35

@BradLevy, thank you, That gives me some confidence and explains why some of my older equipment still functions! Think operating temperature has been in my favour as well as s good safety margin in the voltage rating. I like the point about "Excessive reverse voltage"... a colleague inserted a small electrolytic the wrong way round and the end of the capacitors' life was instant!!! A very loud bang and the can and contents spread over a large area. This was only at 5 or 15 volts, nothing high voltage. I guess if you want long service life and space is not a constraint you need to design out electrolytics. I read an interesting article that PV industry does not use electrolytics and use 'film' types for long life. I wonder what the satellites use or indeed the military by choice? I recall back in the 80's tantalum was the choice, but did not investigate the reasons. Anyway a very good paper Brad and an interesting article Andrew.

July 2, 2020 14:42

@BradLevy Thanks, Brad! I've read bits of advice on e.g. temperature related effects, but that looks like it could be pretty comprehensive and will take a look, appreciated.

July 2, 2020 09:47

Good job!
I always find electrolytic's and 'life' a concern and a mystery! Even one of your replacements states "Panasonic FC Series Type A electrolytic capacitors offer a high endurance, low impedance solution. These aluminium capacitors feature endurance between 1000 and 5000 hours." so although this is at worst case temperature, but an expected life of 40 to 200 days in continuous use?
I could not see a spec that showed endurance against temperature, but hopefully much better!

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July 2, 2020 14:43

@Boss I'm relieved to hear that I'm not the only one who finds electrolytic lifetime ratings a little mysterious, but expect it must mean worst combination of operating conditions (temperature + ripple current etc.) and degradation by some degree — hence not "dead" at this point and rather instead just not performing so well (still a way to go until ruptured and with electrolyte leaking, although hopefully this would never happen...)

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