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 Post subject: KVM switch behaving oddly
 Post Posted: Tue Jun 17, 2014 5:21 pm 
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Hello Folks,

My KVM switch is behaving strangely. It used to work perfectly, but for some time now it will only recognize PC (B) if PC (A) is powered on.

Consequently, I have to run PC (A) when I only need PC (B).

Conversely, if I only need PC (A), that's fine.

It's a 2 port, hardwired, Belkin device with no external power supply. I'm trying to ascertain the actual model, but there isn't much information on it and I can't immediately find any details.

I'm guessing it's a hardware failure, but any advice appreciated.

Thanks in anticipation..

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Tue Jun 17, 2014 5:44 pm 
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What happens if you swap the A and B connections? Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Tue Jun 17, 2014 8:01 pm 
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Same thing Scott,

Nothing changes. I've tried it several times.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Tue Jun 17, 2014 8:37 pm 
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What happens if you switch the mice and keyboards between the systems? Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 4:11 pm 
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I'm not quite sure what you mean, Scott.

This switch is one of those which allow connection of a keyboard and a mouse, but the outputs to the two PCs are hardwired (rather than separate cables), so the only thing I can alter is which cables connect to which PC. I've tried that and the problem persists. No matter which cables run to which PC, I still have to power on PC (A) before PC (B) recognizes the mouse and keyboard.

It never used to be that way though - as I said, the switch worked flawlessly for a long time. I'd just replace it if I could find another one the same, but I can't. I'll probably end up replacing it with a different model at this rate. I've got a four way switch somewhere which I should test with these PCs, but we moved house a while back and a lot of stuff is still in boxes! If I can track down the four-way it will be interesting to try that - not to mention a lot more messy as it's bigger and uglier than the neat little two-way.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 4:16 pm 
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I see, thanks for the clarification. I think it must be something in the unit failing, very likely an aging capacitor. If you open it you might see if you notice any bulging or leaking, and if so try replacing them. I've repaired several components such as amplified speakers, network switches and even motherboards by stealing similar spec. capacitors from junk boards and using them to replace defective ones. Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 4:25 pm 
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Thanks Scott,

I don't have your expertise in this area, but I might try opening the switch and starting the learning curve as soon as I get the time!

Meanwhile, I think I'd better try to track down the four-way switch or buy another model.

If I do manage to repair this unit I will definitely post a reply.

Thanks for your help.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 5:27 pm 
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Scott,

I've just tried an old keyboard with this switch - and it works perfectly!

It seems the switch is fussy about which keyboards it will play with.

Both keyboards are PS2 (ie: no adapters involved).

So all I have to do is revert to an old, beige keyboard my wife has drenched with coffee to the point where the spacebar requires two hits in order to work, and the problem is solved. Or I can buy new keyboards until I find another one which works, or just replace my wife (never going to happen).

Thanks again for your help. Guess I won't be learning electronics just yet!

Regards,

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 5:49 pm 
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Location: Stowmarket, Suffolk England
Dishwasher for the keyboard! Also this might be an excuse for an IBM Model M keyboard!

My KVM is fussy with mice, I have a USB mouse with PS/2 adaptor which works better than some native PS/2 mice.

I want a "universal KVM" with VGA, DVI, HDMI, display port and USB, PS/2 and even Serial at some point.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 6:02 pm 
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Thanks David,

Can I really put a keyboard in a dishwasher?

No idea what an IBM model M is. I'm guessing it's rather expensive. I'll google it.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 6:17 pm 
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Thanks for letting us know the outcome. That is what I was trying to get at when asking you to swap keyboards/mice earlier, but I guess I didn't really state it properly. I wouldn't put a keyboard into a dishwasher, but I would take it apart and clean it with alcohol and/or distilled water. Then reassemble after allowing it to thoroughly dry. The legendary IBM Model M keyboard is considered by many (myself included) to be the best keyboard ever made. Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Wed Jun 18, 2014 7:43 pm 
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Thanks Scott,

Dishwasher option hereby discarded (I was slightly tempted due to the fashion for 'baking' motherboards).

Now I understand what you meant when you asked me to swap keyboards/mice. Just me being obtuse.

Thanks for your time and help. I'll take some keyboards apart and clean them. And I'll check out the IBM model M. if you respect it, it must be good.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Thu Jun 19, 2014 5:31 am 
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Location: Stowmarket, Suffolk England
i PuT aii mY keyB0ards iiiiiinnn thE DisHw3sher with liTTle iLl Efects.

Though I do dismantle them first!


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Fri Oct 17, 2014 5:35 pm 
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Sorry to resurrect an old thread like this, but my question is directly related to the previous posts.

I've been carrying on with the keyboard the KVM switch didn't like, and accepting that I had to boot up both PCs in order for the switch to work.

Yesterday, however, I decided that PC(A) was no longer needed, so I removed the KVM switch and hooked up the mouse and keyboard and both monitors directly to PC(B).

Problem is, PC(B) does not recognise the mouse, keyboard or monitors. When I hit the power button it starts up, reboots immediately, then there's no response from the peripherals, although the PC is running!

I'm baffled. Any help greatly appreciated, to say the least!

For info, the box in question is dual booted with XP and Ubuntu 14.04. Ubuntu is the default OS.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Fri Oct 17, 2014 6:08 pm 
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At this point it sounds like the motherboard, keyboard or mouse may be defective. I've had bad mice and/or keyboards prevent a system from booting (causing a lock-up during the POST) for example. First see if the system will boot up properly without a keyboard or mouse attached (normally it should), if so then try a known-good spare keyboard and mouse. If the system boots up properly with the known-good spares then the original keyboard and/or mouse are likely defective. If the system won't boot up with any keyboard or mouse attached then the motherboard (ports) may be defective. If the existing keyboard and/or mouse are PS/2 connected then try USB versions, else you'd have to replace the motherboard. Let me know what you find, Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Fri Oct 17, 2014 6:21 pm 
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Thank you Scott,

Will do. It's late here, so I'll try tomorrow and post back with the results.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sat Oct 18, 2014 3:31 pm 
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Hello Scott,

No, the system won't boot without a keyboard and mouse. Or with a different keyboard and mouse (both mice are usb - can't put my hands on a PS2 one right now).

Looks like a dead motherboard. Although it's very strange that the MB should function perfectly up to the exact point where I disconnected a fussy KVM switch..

I also can't understand how the PC recognises a keyboard at first (which it does, because I use Ctrl + F12 to boot up), then restarts but doesn't see the keyboard anymore. Not to mention the mouse or the monitors...

This is a weird one!


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sat Oct 18, 2014 3:58 pm 
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Motherboards can be very prone to damage via the PS/2 ports. It is not recommended to connect or disconnect PS/2 devices while the power is on, and I recommend grounding any plugs (as well as your body) before connecting PS/2 devices.

However because it appears to be responding to some keyboard input it might be a configuration issue. I've seen cases where corrupt or improper settings in the BIOS Setup can cause problems like this. I would recommend unplugging the system and removing the CMOS battery to reset all BIOS Setup settings to defaults. Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sat Oct 18, 2014 4:30 pm 
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Thank you Scott,

I'l try that tomorrow.

Mike.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sun Oct 19, 2014 9:40 am 
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Just tried removing the battery for 60 seconds. Still no luck, although I did get a beep code which seems to mean "Display card or monitor connected error".

The Post Code on the board itself (while running) was showing 7F which, according to Abit's manual means

"Switch back to text mode if full screen logo is supported
-If errors occur, report errors & wait for keys
-If no errors occur or F1 key is pressed to continue: Clear EPA or customization logo".

Could it be that the display card has failed? Bit of a nuisance to test because the motherboard has no on board display output, but it may be worth my time swapping in another card..


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sun Oct 19, 2014 2:08 pm 
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The video card is definitely suspect here. I'd swap in a known-good card as a test. Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sun Oct 19, 2014 4:03 pm 
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Thanks Scott,

I'll do that. May not be for a few days though, due to sheer lack of time, but I'll definitely let you know the outcome eventually.

Incidentally, how would you ground any plugs or your body before plugging in PS/2 devices? I see people recommending I connect myself to the national grid or a radiator, but as I understand it, I just need to touch the PC case to ensure I have the same electrical potential as the computer. Am I misunderstanding this? I always turn off a computer before plugging things in (usb and audio cables excepted) and definitely before plugging/unplugging a power cable..


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sun Oct 19, 2014 6:29 pm 
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I merely touch an unpainted part of the chassis with my hand and with the metal shield on the connector before plugging it in. That insures that myself, the device being connected and the system are all at the same electrical potential before making a connection. Nothing more elaborate is required. Scott.


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Thu Oct 30, 2014 9:11 am 
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Thanks again Scott,

Still haven't had chance to try a new card - actually we've just moved house and I'd be lucky to find the computer at the moment!

When I do eventually try it, I'll post back with the outcome.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Sun Nov 16, 2014 2:10 pm 
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Finally got chance to swap in a good video card, and I'm back up and running! Thankfully I don't need to replace the motherboard.

Thanks for your advice Scott.

Mike


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 Post subject: Re: KVM switch behaving oddly
 Post Posted: Mon Nov 17, 2014 12:40 am 
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Glad it all worked out, and thanks for letting me know the outcome! Scott.


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