I'd like to try to fix this notebook if I can. I thought it had a dead CPU fan because it does not run. Even when I go into the BIOS and sit. I have a second one of these for work and it runs the fan pretty fast/high when in the BIOS. So I ordered a new fan from eBay and it came today. Plug it in and it does the same thing. I connected up the original fan to my bench supply at 5V and it runs, so the original fan does work and both fans exhibit the same behavior. Now I'm thinking there is something wrong about the way it is being driven. It is a 4 pin port with black (ground), red (5V), yellow, and blue. I *think* yellow is the tach and blue is the control based on some Internet searching. I found if I connected up only the black/red that the fan would run so through trial and error I disabled the yellow (no run), the blue (runs), put back the yellow (still runs). It seems that with the control/pwm blue wire connected, it does not run, or I think I saw it run once really slow when it was int he BIOS and it should have been running full speed probably. Just to get my system up and running I pulled the blue wire out of the wire harness and am running it on the black/red/yellow, but as expected, the fan runs pretty much full speed all the time, when the CPU needs more cooling and when it doesn't.
Any tips on what to look at next? I've already carefully resoldered the 4 smd pins for the connector on the PCB to make sure they are all a decent connection. That didn't change anything. Should I try to get a scope on the blue wire and see if there is any kind of signal? I'm not sure the trace for it is visible on the pcb.
Also, as a second question, I loaded a program called core temp on both Dell 5770's. My work one seems to really shoot up on the CPU temperatures, not only do they jump around quite a bit, but it thinks nothing of jumping into the 90's deg C. It says Tj Max 100 C, but Im surprised it jumps around to much.
Home
Help
Search
Login
Register
