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Tech Helproom


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USB Keyboard on a PS/2 input


dms_05

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I've used a small adapter with USB female and PS/2 male to connect a USB keyboard and a USB mouse to a KVM switch with PS/2 female inputs for keyboard and mouse. This has worked well for a considerable time. I've now replaced the keyboard with another USB keyboard and simply plugged it into the female end of the adaptor. It doesn't work. Why?

I've tried the USB keyboards plugged directly into my laptop and they both work (W7 64 bit). I've even tried using a number of USB female to PS/2 male adaptors and some work and some don't even though they look absolutely identical.

Anyone any idea why this is happening (I've read a bit via Google and some recommend 'active' adaptors but can't explain why some USB keyboards work and some don't, the nearest possibility is some older keyboards draw a lot more power than modern keyboards but both of mine are modern keyboards).

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woodchip

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Only thing I can think is they are wired different. Have some of those adapters

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woodchip

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PS Mine come in two colours it may be you are using the wrong colour Purple for Mouse Green for Keyboard, I think.

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wee eddie

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Is there any possibility that the new keyboard needs more Power than the old?

USB is certainly designed to deliver more Power than PS2.

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spuds

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I use USB to PS/2 adapters of various combinations on a regular basis for ages, and have never really had any major problems. At the present time I am using a similar set-up to yourself with a D-Link KVM switch.

Having said that, once I did try a PS/2 mouse and it just wouldn't work with the present set-up, but it did as a sole unit, and I never did find out the reason why.

With regards to the power thing. I think this is more to do with USB hubs than anything else. Some devices require powered hubs, when other devices do not, and work just as well.

I do not use W7 and know very little about it. Is there any message about 'new hardware' recognised when trying to connect the new keyboard?.

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dms_05

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I've tried all combinations of purple and green adaptors. Some work on both keyboard and mouse and some don't work at all. Even so none work on the second (new) USB keyboard.

I found the following "ps/2 and USB ports can use different voltages... quality usb adapters have an integrated circuit that compensates the PS/2 - USB port voltage differences so it's advisable to avoid cheap adapters or rather try with a usb keyboard or mouse." which probably explains the problem. However it's odd that some adaptors (probably all the non-compensating variety) work and some don't. Also newer USB keyboards require a lot less power than PS/2 ones so it seems not a power problem but a voltage problem (however even then PS/2 requires 4.5 to 5.0 volts which is much the same as USB produces).

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connectpro_rex

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What's the second set of USB keyboard and mouse of this case ? Not every USB devices create equally. The USB-PS/2 converters only work for those USB devices with simple "USB endpoint".

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