ASUS TUSL2-C rear USB ports not working - voltage too low

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ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-23 @ 06:54

So now that I have the rig built mostly, and things are starting to be stable and set up, I decided to figure out why the rear IO USB ports don't work.

I've tried several keyboards and mice, as well as flash drives but nothing seems to work.

Thinking about this, I recalled how pre-3.0 USB only had 4 wires, +5v, GND, and 2 data wires. A quick search reminded me that the two outside pins in an A connector are the +5 and GND pins.

Pulling out my trusty multimeter, I measured the voltage on both of those ports power pins and am a bit surprised by the results... the lower port (closer to the PCB) is ~ 2.05v , and the higher port (farther away from the PCB) is ~ 1.99v

Now... call me crazy, but 2 volts is a lot less than 5 volts. This explains why nothing plugged into those ports is working, but now the question is why would the voltage be so low?

Another interesting quirk is that the USB header on the board works just fine - I connected one of those slot expansion brackets and tested several devices going through the header and it is just fine so there's nothing wrong with the USB controller itself - just something funny going on with those ports on the rear IO...

Any suggestions on what I should look at next to hopefully fix them?
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby Dominus » 2019-6-23 @ 07:19

I remember owning a CUSL-C (or similar - I don't remember exactly) with flaky rear ports but working fine interior port.
Maybe it's just a flaw
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-23 @ 18:54

Dominus wrote:I remember owning a CUSL-C (or similar - I don't remember exactly) with flaky rear ports but working fine interior port.
Maybe it's just a flaw

ooh that's good to know, thank you.

I'm going to try replacing the socket with a brand new one and see if that helps. The housing looks pretty oxidized so it wouldn't surprise me if the pins internally are just decayed to the point of not conducting well enough to work properly. Will update once I have soldered the new one on with the results!
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby Thermalwrong » 2019-6-23 @ 19:32

Try setting the USBPWR01 jumper to 1-2 instead of 2-3 if it's on that, the manual warns that a weak 5v Standby rail (less than 2a) could cause problems with the USB. It's not like there's a voltage regulator for USB, but your PC is working, the first thing I thought was maybe a bad PSU? But I think you'd notice if 5 volts isn't working properly. Maybe a bad 5v standby rail could cause this problem?
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-23 @ 19:42

Thermalwrong wrote:Try setting the USBPWR01 jumper to 1-2 instead of 2-3 if it's on that, the manual warns that a weak 5v Standby rail (less than 2a) could cause problems with the USB. It's not like there's a voltage regulator for USB, but your PC is working, the first thing I thought was maybe a bad PSU? But I think you'd notice if 5 volts isn't working properly. Maybe a bad 5v standby rail could cause this problem?


I'll try that jumper. Those 2 ports have been non-working the entire time with all PSU's tested though (currently using a brand new Corsair HX1200). I haven't tried enabling USBPWR on either those rear I/O ports or the header, but as I mentioned the header works just fine already.
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby Bige4u » 2019-6-23 @ 22:07

My apolagies, for im not much help for an answer to the low voltage situation... but i've used that same motherboard in the past along with WIN98 installed and just added a 4port usb2.0 PCI card, so perhaps forget about using all the onboard usb ports.

Just go with a usb2.0 PCI card, works perfect and much more reliable IMO, unless you're really handy with the desoldering iron, dont risk it, you might damage the rest of the motherboard by accident leaving it inoperable, those motherboards are getting a little harder to find nowadays and expensive.

Good Luck
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby Intel486dx33 » 2019-6-23 @ 22:38

What OS are you using?
If you are using Win95 or 98 you need to install the USB update patch.
I think it’s called “nUSB”.

Here are some USB pin-out connection diagrams.
I use an USB extension cable from the motherboard to the front USB connections if your cables are too short.
Make sure you don’t get your wires crossed,
Separate the USB port-1 wires from the USB port-2 wires.
Pins 9 and 10 are nothing ( dead ). Not needed.

Wires color code:
White - data -
Green - data +
RED - 5v, Vcc
Black - ground
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-24 @ 01:34

Bige4u wrote:My apolagies, for im not much help for an answer to the low voltage situation... but i've used that same motherboard in the past along with WIN98 installed and just added a 4port usb2.0 PCI card, so perhaps forget about using all the onboard usb ports.

Just go with a usb2.0 PCI card, works perfect and much more reliable IMO, unless you're really handy with the desoldering iron, dont risk it, you might damage the rest of the motherboard by accident leaving it inoperable, those motherboards are getting a little harder to find nowadays and expensive.

Good Luck

Thank you! - I do actually already have a usb 2.0 card installed, but that doesn't help until Windows loads (IE had to dig out a PS2-compatible keyboard and USB to PS2 adapter to get things set up since the rear USB ports are not working). Now that I know the internal header still works I could use those with a rear panel expansion bracket but I'd like to get this thing 100% functional.

Soldering parts this large is not much worry for me, and I have desoldering braid, flux, quality leaded solder etc so it should only take me 5-10 minutes to replace the socket once it arrives.
Last edited by kalm_traveler on 2019-6-24 @ 01:39, edited 1 time in total.
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-24 @ 01:39

Intel486dx33 wrote:What OS are you using?
If you are using Win95 or 98 you need to install the USB update patch.
I think it’s called “nUSB”.

Here are some USB pin-out connection diagrams.
I use an USB extension cable from the motherboard to the front USB connections if your cables are too short.
Make sure you don’t get your wires crossed,
Separate the USB port-1 wires from the USB port-2 wires.
Pins 9 and 10 are nothing ( dead ). Not needed.

Wires color code:
White - data -
Green - data +
RED - 5v, Vcc
Black - ground

Hi there - I am running Windows 2000 at the moment, planning on adding a dual boot option for either Windows Me or 98SE next weekend. As I mentioned in the OP, the 2 ports from the motherboard internal header work just fine, and this is definitely a hardware problem specific to only the 2 ports on the rear I/O part of the motherboard.

As you reiterated, USB ports should have +5v and GND for power, and 2 data pins, but when measuring those 2 non-working ports on my board they are both only reading approximately +2v (the lower one is just above 2 volts and the higher one is just below 2 volts) so something is definitely skewompus with them.

I bought a new socket to replace that original one for about five dollars, and am very capable of replacing it in 5-10 minutes so hopefully that will do the trick. Given that the motherboard header USB ports still work properly my guess is that the metal of this original socket has just corroded internally so it isn't making good connection with the PCB anymore.
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby kalm_traveler » 2019-6-24 @ 03:11

decided to prepare for the new port since I had a few minutes tonight - removing the old one was more work than I'd expected but it's out and I didn't melt anything so that's a win :happy:

20190623_210522.jpg
no more USB ports
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Re: ASUS TUSL2-C rear USB ports not working - voltage too low

Postby photomaster » 2019-9-11 @ 22:37

@kalm_traveler

Hey man, have you managed those USB ports to work?
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