ADC with bad USB

[waynestewart]

In the last bit, I've had a few 17" ADC Cinema LCD displays pass through my hands. It seems like in more than half of them the USB port isn't working. I know it's not the video cards as I've also tried them with a known good DVI adapter. I was wondering if I just chanced on a bad bunch or is this usual?

 

[techknight]

Um im lost, how does USB have anything to do with video cards and DVI? if the monitor has USB ports, there should be USB pass-through cable, basically its a USB-hub seperate inside the monitor.

 

[waynestewart]

Not with ADC. The Mac LCD ADC monitors have only the one cable. It had power, video signal and USB in the one connector. The video card supplied all of it, power, video and USB.

Apple later made an adapter to let you use those monitors on other computers without ADC video cards. The adapter was a power supply and had cables to plug into DVI and USB.

 

[beachycove]

I have had three of them with no problems experienced with USB — other than the fact that it's not USB2! Backlighting/ inverter board problems are what I have seen.

I seem to recall that the ADC displays gave out an unusually high current to USB devices. Could it be that the components regulating this are getting tired?

 

[Trash80toHP_Mini]

If the components were putting too high a voltage on the bus, check to see if there's any USB, or enough, current making its way through that nightmarish video interface. If not, try hooking up a powered hub to the monitor to see if it works again?

 

[waynestewart]

I tried two different powered USB hubs and nothing.

Tried both USB ports on the 17" Cinema display

Tried two different machines

Was using a Keyboard and mouse.

Same results using Apples DVI adapter

 

[Trash80toHP_Mini]

Bugger! :-/

 

[Dennis Nedry]

Is the USB hub in the display supposed to show up in System Profiler like the hub in a keyboard? That might shed some light.

Also - could you test these ports for if they are getting 5 Volts like they should? One way to test this is by plugging some sort of device that charges off of a USB port and seeing if it starts charging. If you're just missing the 5 Volts, that probably wouldn't be too terribly hard to fix.

 

[waynestewart]

The hub in the monitor does show up in System Profiler.

Wouldn't lack of 5 volts be solved by connecting with a powered hub?

I don't have anything that charges off USB but I can likely try volt meter

 

[Dennis Nedry]

I don't know if a powered hub would fix that or not. I think that it would fix it if the +5V line was disconnected, though I'm not sure what would happen to the signal without a common ground if that got disconnected. Testing for power could at least give some useful clues.