5VSB refers to a specific PCIe version used in some graphics cards, not a motherboard shortcut.
5VSB refers to a specific PCIe version used in some graphics cards, not a motherboard shortcut.
Hey there! I’ve got a used motherboard that’s been sitting around for a while, and it’s mostly for a steal—just a free Q9550. I’m trying to get it running Windows XP or Vista just for the nostalgia factor. The seller warned it won’t work, but I’m hoping it’ll turn on eventually.
The main issue is that it powers up but doesn’t display anything on the screen (it’s using a dedicated GPU). When I connect my speaker and power it on, there’s no sound at all. Also, the motherboard has a debug LED, but it doesn’t light up or show any codes—possibly a faulty BIOS chip.
I’ve checked every pin on the 24-pin connector and the CPU power connector with a multimeter; everything looks fine except for the 24-pin rail. There were beeps when I checked pin 9 (+5V), but only when the ground was connected at pins 7 or 15. If any other ground pin is used, it doesn’t trigger a beep.
On top of that, I removed the heatsink and thermal pad for the chipset and MOSFETs because they looked old and possibly damaged. The area around them showed signs of liquid damage, but I’m not sure if any actual fluid got inside. It might just be dust or something stuck.
Since I’m new to using a multimeter and measuring things, any advice would be super helpful!
If the surface appears damp, it's likely due to the silicon oil from thermal pads—nothing to worry about. If it shows signs of corrosion and green discoloration, there may be an issue. When searching for short circuits in PC parts, avoid using continuity mode since many components have low resistance by default. Continuity mode sounds when resistance drops below 10 ohms, which is probably the case (the exact number varies). In computer hardware, you often encounter resistances between 2 to 3 ohms or lower—such as the core resistance on a 1080 Ti processor, which is about 0.08 ohms, well within the range most multimeters can detect. However, when dealing with higher resistance components (over 100 ohms), a short might exist between them and another rail (like 50 ohms), but continuity tests won't detect it between that part and ground. Always measure the actual resistance and share the results.
Total new info alert! I see two different readings (pin 18 and pin 15). If ground connects to pin 18 or something like the PS2 port casing, I get these values: 1 68.2 set 200 2 4.79 set 20k 4 .665 set 2k 6 0.7 set 200 8 0.7 set 200 9 .434 set 2k 10 0.6 set 200 11 68.2 set 200 12 68.1 set 200 13 0.7 set 200 14 .433 set 2k 16 .434 set 2k 20 0.6 set 200 21 3.32 set 20k 22 0.7 set 200 23 17.14 set 20k If ground is set to pin 15 I get: 1 196 set 200 2 5.28 set 20k 4 1.095 set 2k 6 192 set 200 8 192 set 200 9 0.6 set 200 10 192 set 200 11 195.8 set 200 12 195.7 set 200 13 192 set 200 14 0.6 set 200 16 0.6 set 200 20 191.8 set 200 21 3.76 set 20k 22 191.7 set 200 23 16.85 set 20k Are these normal? The pins I tested on the ATX connector are the first column 1,2,4,6 etc.
I examined a few of those that caught my attention (pin 16 showed two different readings, for example) and they mostly matched (+-10%) on my Rampage III Formula board, which is the closest working setup I have. It’s likely the ground plane configuration is the issue. The resistances look reasonable. If you’ve verified there are no shorts from VCore to ground, PLL to ground, VDIMM to ground, and all smaller rails to ground, it’s time to power up the board and test each voltage rail. If they’re all there, the chipset might be faulty and the board could be unusable. You might attempt a reflow, but success isn’t guaranteed.
on the 8 pin CPU connector I see 12v across all four pins that are meant to carry 12v. This matches what I expect from the 24 pin connector where I get 1.3v, 2.0v, 11.98v, and 12v. The values seem a bit inconsistent at first glance, but since I'm just starting out, it's normal. I'm learning this as a hobby, and the CPU tends to get quite hot. The chipset is warm, and I haven't added anything to the motherboard except the CPU and CMOS battery—no BIOS chip yet.
The important voltages here are the output voltages from the VRMs, so you should check ground connection. You can either test across a capacitor or from a choke to ground. The ones I noticed are these. There could be others, but it's 2AM and I'm new to LGA 775. The photos I found are low quality, so there might be more. This is just a beginning—measure them and see the readings.
Everyone appears correct. The 12 and 5V units handle input filtering, while the range from 0.5V to 2V manages output filtering. These levels look accurate, suggesting the chipset or CPU might be inactive. If the board lacks a CPU, do you receive a POST code or just silence?
it seems the device behaves oddly after being powered off. when i pressed the power button and then unplugged it, it took about a quarter of a second to respond. afterward, it consistently showed 5v on most pins except for a few that stayed low. i tested it without any cpu, ram, or bios chip—just basic components—and even with no pcie switch card, it kept staying on. the chipset and southbridge were warm but not overheating. every component around it was either getting 1.1v or 1.5v. i asked the seller about its use, and he mentioned it was built for mining with two gpus. he said one day it shut down suddenly, never coming back. my thought is a power issue might have happened, which is common in his area. what do you think?