Solid lit hdd light. Second motherboard with the same problem.

[mscpmike]

I have a 990FXA-UD5 motherboard. The HDD light stays on solid no matter what when power is applied. I have tried running the board with nothing connected at all except power and the same thing still happens.

Before I bought the UD5 I had a UD3 that did the same exact thing. I returned the UD3 because it ran way too hot, and there were complaints about how hot the board ran.

I love the UD5, but still have the same problem with HDD light. Has anyone else experienced this? Did you find a resolution to the problem?

[klh591]

You have the HD wire from the case connection to the motherboard backwards.  In other words, you have the positive and negative wires connected
to the wrong pins on the motherboard.

[mscpmike]

An LED does not work at all if you reverse polarity. It either lights up on correct polarity, or does not all on reverse polarity. I have tried the other way, which is reverse polarity, and there is no light at all.

It's not the pin polarity.

[klh591]

I'm sorry but you are wrong!   I tested my theory before my post on my own UD5 and that is what happened.  It is sitting right next to
it and it is solid red when the wires are reversed.  When they were on correctly the light flashes only when drives are accessed.
I've had this happen many times over the last  thirty years with different cases and motherboards so I know what to check.

[mscpmike]

I'm sorry, but YOU are wrong. LEDs only flow current in one direction to produce light output. It's on one way, off the other. The light you are testing with is not an LED if it is lighting up in reverse.

Electrical polarity of LEDs:

As with all diodes, current flows easily from p-type to n-type material. However, no current flows and no light is emitted if a small voltage is applied in the reverse direction. If the reverse voltage grows large enough to exceed the breakdown voltage, a large current flows and the LED may be damaged. If the reverse current is sufficiently limited to avoid damage, the reverse-conducting LED is a useful noise diode.


I'm not looking to get into a pissing contest. I have attempted two other LEDs with the same result.

[klh591]

I just reversed the case HD wires on the 5 active computers + 2 test computers in my house and rebooted them all.   The light became solid on ALL
7 computers.  I then reversed the case HD wires to the correct position on ALL seven computers and the lights only came when the SSD's or hard
drives were accessed on each computer.  I have over 40 years of computer hardware experience beginning with IBM mainframes in the early 70's
and have been putting PC together for over 30 years.   I also have a number of PhD's and patents in the computer field where I have learned that
experience many times is better than theory.  My best patents were when theory DID NOT work but puttering DID.

[MisterEd]

I know it may seem dumb but it never hurts to double check.

Hard Drive Activity
F_PANEL: Hard Drive Activity LED (1 & 3)
CASE FP: HDD LED

Computer Power
F_PANEL: Power LED (15 & 19)
CASE FP: Power LED

Pins on motherboard header F_PANEL:
Pin 1: HD+
Pin 3: HD-
Pin 15: PWR+
Pin 19: PWR-

[MisterEd]

I just reversed the case HD wires on the 5 active computers + 2 test computers in my house and rebooted them all.   The light became solid on ALL
7 computers.  I then reversed the case HD wires to the correct position on ALL seven computers and the lights only came when the SSD's or hard
drives were accessed on each computer.  I have over 40 years of computer hardware experience beginning with IBM mainframes in the early 70's
and have been putting PC together for over 30 years.   I also have a number of PhD's and patents in the computer field where I have learned that
experience many times is better than theory.  My best patents were when theory DID NOT work but puttering DID.

I agree with that. I learned more from puttering than any of the college courses I took. This first-hand knowledge paid off when I was a technician and later when I was an engineer. I have owned a computer since 1980. It wasn't until I started taking them apart and experimenting with them did I really learn about how they worked.

[CountMike]

Got me confused for a second, so I checked with 3 of my computers at home and LEDs did not come on even for a second when polarities were reversed. Spend most my life experimenting and working with electronics (no PHDs and stuf but was instrument technician with few years at aircraft instrumentation maintenance) and never managed to have an ordinary LED to light up with DC polarity reversed, however at some frequencies with square wave AC they will light up, also there are some tri-state LEDs that work in both directions and with AC too but with different color for each state. So it is not impossible that in some circumstances they will work as described, it's just that mine did not. By definition LED is diode and I used them as diodes in ordinary way, light or not. I also worked with and at computers since '70ies and was radio amateur since grade 4, 1959, so I gues I have some credentials there too. So to conclude, normal, ordinary LEDs do not light up with DC polarity reversed, that's why they come with one lead longer or otherwise marked so polarity is known without testing.
PS. Oh yeah there is a way to have them light up with polarities reversed but it involves using rectifier bridge so it is not practical for very small packages.
MBs tested on are:
GB 790xt-USB3
GB 870a UD3
Asus m2n-CM DVI.
I know for sure that LEDs with reversed polarity did not work on any older MBs I ever used (many a time I accidentally reversed them) but it may be the case with newer ones although this is first time I ever heard of such cases.

[Vezina]

A LED is a diode so it will only light when properly connected ,in only one way conducts electricity ,the other state is the closed/locked one  

Unless the LED is a 2 color one .
If it s a 2 color LED it will light in both ways ,but with a different color.In this case 2 diodes are connected in parallel ,but they are reversed connected.
Bicolor LED-s can be 2 legged or 3 legged though.

[auscos]

OP, did you ever work it out? Creating an account to post here because I experienced the same problem and this thread figured high in the Google rankings. You are almost certainly correct about not having the pins around the wrong way. Of course that was the first thing I tried in troubleshooting the problem and like you I found that the LED never illuminated with that orientation, because it's a diode, like you said.

I measured the pin voltage and found the potential sitting at +3.8v (I think, I didn't write it down) when the motherboard had power but was off, then dropped to near 0 when the machine was turned on, after which it seemed to operate normally.

The problem turned out to be a cheap USB/SDcard panel powered by one of the mylex plugs that I guess doesn't properly isolate its power supply from the voltage lines in the USB cable to the motherboard. It looks like it was leaking potential from the power supply back into the power pins on the USB header on the motherboard, which probably shares some circuitry with the HDD LED headers.

Anyway, I'm not comfortable with stray voltage in the motherboard so I've unplugged that device and all is operating normally. Another guy I read had the same problem fixed it by re-seating the SATA cables. Anyone else who hits this page - check every storage device connected to the motherboard.

ETA, I've got a brand new GA-990FXZ-UD3 R5