I got a Jetway JNC9C-550-LF mini-ITX mobile Atom board from Newegg to run sandeen.net, and the plan was to run it off a Pico-PSU 90W [amzn] power supply for maximum efficiency. But I could not get the darned thing to boot on that power supply. It worked ok on a 250W ATX ps, though. I had originally gotten an 80W picoPSU, and that failed to boot, so I RMA’d it. The folks at mini-box were very nice and helpful, but the 90W behaved exactly the same way. I was stumped. As a long shot, I asked Jetway tech support about it, and was rather astounded to get this reply:
(reposting here in the hopes that it will help others)
Thank you for taking the time to write to us with your concerns. I am happy to assist you further.
We have reviewed your request regarding JNC9C-550-LF. According to your statement, we think it is something related to the power supply.
We have experienced some minimum load issues with the following power sources:
1. IEI ACE-4518AP
3. M3-ATX 125W
4. Power-win PW-085B-5Y
Our solution for above powers is:
1. remove D9
2. remove R163
3. change Q30 from C01-E7002-F to C04-EAPM2300A-F
4. change R270 from E01-42B1.8K-F to E01-42B3.3K-F
You can try to remove D9 & R163 first. Our test has shown it can work with picoPSU when only remove these two parts.
We hope this update has been helpful. However, if you have any additional questions, please don’t hesitate to contact our Technical Department.
I’m rather amazed that they would suggest reworking the board, and I’ve asked what this will do to my warranty (!) and whether newer revs have this fixed. Still, this is quite an interesting reply IMHO, I didn’t expect to learn this much! They also attached pictures of the components:
I don’t know if I’ll go after it with a soldering iron or not, but at least the mystery is solved!
Update: Jetway tells me that newer boards have this problem solved.
Update 2: It works! Removed the diode and the resistor and it’s booted up fine. 20W server here we come!