[rescue] SUN IPC woes

[Todd Vernon]

 I’ve successfully used this to replace the PSU in one of the lunchboxes
https://github.com/hanshuebner/ipx-psu-replacement

I’ve also put one of these 1u ATX supplies in another although I used a
combination of the PWU space and the hard disk space to make it work.
https://www.amazon.com/Modular-Small-1U-110-220V-Motherboard-Interfaces/dp/B0DHYZZ1JS

-t

Todd Vernon
Entrepreneur | Investor
Email: todd at toddvernon.com
LinkedIn: toddvernon <https://www.linkedin.com/in/toddvernon/>


On Aug 4, 2025 at 8:32:35 AM, Patrik Schindler via rescue <
rescue at sunhelp.org> wrote:

> Hello Hauke,
>
> some thoughts from my electronics knowledge…
>
>
> Am 04.08.2025 um 15:33 schrieb Hauke Fath via rescue <rescue at sunhelp.org>:
>
> The "exothermal" one had blown its fuse, and suffered burns on the
> transformer's primary side, unsoldering one pin and flat out losing a
> second one. I am kind of reluctant to hook it up to the grid.
>
>
> Broken soldering spots are relatively common in PSUs. Mechanical
> vibrations from the transformer itself due to the magnetic field stress the
> soldering spots over time. Sometimes they crack. Then flashovers in the
> loose tin grain generate heat and lead to the situation you've seen.
>
> If you manage to fix the soldering spots, the main issue is gone. It might
> happen that there are more defects due to the cracked spots, but that's
> rare.
>
> Use a multimeter in ohms setting, and measure across the bridge rectifier
> + and - pins. You'll see or hear a beep signal indicating almost a short
> for some seconds until the primary caps charge from the multimeter
> batteries. If the meter reading doesn't change from the indicated short
> after 10 seconds, main causes are:
> - switching transistor shorted
> - bridge rectifier shorted
> - other circuitry shorted
>
> Desolder the components (or single pins thereof) and measure until the
> short is gone. Then you have the culprit.
>
> If you can't measure a short, there's no way around: Plug in and test. :-)
>
> All in all, it's always a good idea to resolder each and every grainy
> looking solder spot, especially when they're supporting large and heavy
> components, or those which become hot. You can tell this by the PCB being
> browner around/beneath those.
>
> The second one shows a short blip when switching on, then nothing - a
> frequent and mysterious error pattern, it looks. I might unsolder the
> transformer, since I practiced on the "exothermal" already.
>
>
> A tiny working period ("blip") might indicate a short on the secondary
> side. Use a known good PSU to check the machine. If it's not the machine,
> there might be a short within the faulty PSU on a secondary. Use your
> multimeter in ohms setting as directed above, to measure the individual
> power rails (5V, 12V, etc.) for shorts, and try to isolate the fault.
>
> If it's not a short on the secondary, there might be problems with other
> components. A good start would be the optical coupler. This is a device
> which provides electrical insulation between primary and secondary sides of
> the PSU, and feeds back voltage level information to the regulating circuit
> on the primary side of the transformer. Details are highly individual per
> PSU manufacturer and an are where I also lack experience and skill.
>
> Anyway - the restored PSU lead to more problems... Powering on the IPC
> gave me
>
>
> PROM Checksum test
>
>
> on the serial line, then silence. Status, or error? When I pulled the
> NVRAM, I got
>
>
> PROM Checksum test
>
> Context Reg Test
>
> Setting Segment Map
>
> Sizing Memory
>
> Mapping ROM
>
> Setting up RAM for monitor.
>
> Setting up memory used in decompress.
>
> Decompressing code to RAM ...
>
> Remapping monitor's virtual addresses to RAM.
>
>
> and letting it sit over night didn't give me any more.
>
>
> Does not sound PSU related.
>
> :wq! PoC
>
>
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>
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