Old AT power supplies - how to test?
Hey folks, I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time. I was thinking before powering on: - Open the PSU - Air spray the PSU - Look for obvious signs of failure - capacitor leakage, burnt PCB, burnt components If all looks OK - do these require a load, or can I at least test basic voltage with no load? I do have heat resistors (used to balance out ATX PSUs for a 3D Printer) that I believe I can plug in on the 5V or 12V rails and test voltage there.. How much testing should I do / what do you recommend? Thanks! John
This is helpful: https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578 <https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578> -andy
On Dec 28, 2019, at 10:05 AM, John Heritage via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
Hey folks,
I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time.
I would suggest doing a visual inspection of the capacitors in the power supply and on the motherboard first. If you have a good capacitor tester that will check for ESR, that's what I use just to make sure the caps are good. If they look questionable replace them. I normally load Each separate supply down with a 10 ohm 10 Watt resistor and run the supply. If you have a 20 W resistors it could be better, a little less heat, but still would load the power supply for testing. Mike R. Sent from: My extremely complicated, hand held electronic device.
On Dec 28, 2019, at 10:18 AM, Andrew Diller via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
This is helpful:
https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578 <https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578>
-andy
On Dec 28, 2019, at 10:05 AM, John Heritage via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
Hey folks,
I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time.
For testing you can really just hook up a junk hard drive or something like that, should provide enough load for the supply to turn on and you can measure to see if voltages are within spec.CJ -------- Original message --------From: John Heritage via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> Date: 12/28/19 10:06 AM (GMT-05:00) To: vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> Cc: John Heritage <john.heritage@gmail.com> Subject: [vcf-midatlantic] Old AT power supplies - how to test? Hey folks,I have a couple of old DOS/Win98 (OS/2) era systems that I came across, andthey both have AT PSUs I want to check out before powering on for the firsttime.I was thinking before powering on:- Open the PSU- Air spray the PSU- Look for obvious signs of failure - capacitor leakage, burnt PCB, burntcomponentsIf all looks OK - do these require a load, or can I at least test basicvoltage with no load?I do have heat resistors (used to balance out ATX PSUs for a 3D Printer)that I believe I can plug in on the 5V or 12V rails and test voltage there..How much testing should I do / what do you recommend?Thanks!John
On 12/28/2019 10:05 AM, John Heritage via vcf-midatlantic wrote:
Hey folks,
I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time.
I was thinking before powering on:
- Open the PSU - Air spray the PSU - Look for obvious signs of failure - capacitor leakage, burnt PCB, burnt components
If all looks OK - do these require a load, or can I at least test basic voltage with no load?
I do have heat resistors (used to balance out ATX PSUs for a 3D Printer) that I believe I can plug in on the 5V or 12V rails and test voltage there..
How much testing should I do / what do you recommend?
Thanks! John
IBM used to sell a load kit for the AT (typically called a sandbar due to the appearance of the load resistors inside) as some of the older PSU would loose regulation and essentially self-destruct without a load Made a home-brew version with a pair of Dale 250W, 20 ohm resistors. The first is +5 to ground, the second is +12 to ground. A later addition was a 12 volt fan. As to the test, I usually I set it up and let it run for an hour with the above load, with a scope to measure voltage and ripple. Martin
You can buy AT powersupply testers. Beware, the cheaper ones just light an LED if there's any voltage at all present. This is not good if the voltage is high enough to destroy a motherboard. Better ones actually give you pass/fail on each different voltage. The typically have multiple connectors on them to work with different era power supplies, as the number of connectors and number of pins on the big connector have changed over the years. I think I have this one: amazon.com/Computer-PC-Tester-Connectors-Enclosure/dp/B076CLNPPK The present the minimum load possible to get the supply to run. For a load test, follow the recommendations of others on this list. Bill Dudley retired EE This email is free of malware because I run Linux. On Sat, Dec 28, 2019 at 10:06 AM John Heritage via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Hey folks,
I have a couple of old DOS/Win98 (OS/2) era systems that I came across, and they both have AT PSUs I want to check out before powering on for the first time.
I was thinking before powering on:
- Open the PSU - Air spray the PSU - Look for obvious signs of failure - capacitor leakage, burnt PCB, burnt components
If all looks OK - do these require a load, or can I at least test basic voltage with no load?
I do have heat resistors (used to balance out ATX PSUs for a 3D Printer) that I believe I can plug in on the 5V or 12V rails and test voltage there..
How much testing should I do / what do you recommend?
Thanks! John
participants (6)
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Andrew Diller -
John Heritage -
Martin Flynn -
Sentrytv -
thedestructionchannel2000 -
William Dudley