Ghosting on monitor from cheap KVM cures...

[Soybomb]

So this weekend I was at a computer show and picked up a $25 KVM switch. Its generic and similiar to the one that newegg sells. Well as I feared.....even when using what seems to be a quality set of cables, I get ghosting at 1024x768@75hz. Crap.

At this point I figure I'll either ebay the pos or see if I can "aid" the problem. Well I opened it up. Its pretty crude inside. On the back panel are screwed on a bunch of ports and the front has a large rotary switch. Between them are a ton of tiny little soldered wires, all individual strands and no twisting or anything. I can't help but think that if it had been made with some twisting like cat5 it would have helped, but otherwise they're just little thin unshieleded pieces.

Does anyone think it will help if I say take a ferrite core and put it around each of the vga leads and try to put some sort of metal jacket around each bundle of vga wires, that run from the port to the switch or am I wasting my time? What do you think?
Thanks!

 

[RayH]

Ghosting is probably caused by signal reflections at contact points. You might try some electrical contact or tuner spray on the rotary switch.

 

[highwire]

The KeybrdVidMouse switchbox prob - "ghosting" - I assume you are talking about leakage of the OFF video through the box to the monitor resulting in a faint image from the wrong system being displayed.

Some background: The standard VGA connection is 3 separate color sig/ground circuits - RGB. If the connections were a differential pair scheme like cat5, the twisted wire thing could be very effective depending on the layout of the switch.

Yeah sure, twisting, shielding might be well worth a try. Also, keeping the A and B video wires as far apart as possible, the object being to reduce capacitive coupling to just the switch itself.

I don't know where you're going with the ferrite bead thing. If you bead any video RBG sig wire, it is almost sure to screw up the video quality. Maybe beading the wires as a pair - sig/ground through the bead as a pair of wires might have some good effect, causing the circuit to act as a balanced differential pair at high freqs.

 

[Soybomb]

Actually when I say ghosting, what I see is a faint ghost image of the real display shifted just slightly off to the bottom and right like 1cm in both directions. Like a very faint transparency. If you've ever used a crappy monitor extension cable,you'll know what I mean I found a guy with a high quality kvm and he's gonna be sure the cables I have are good too.

Yeah the ferrite thing might have been a bad late night idea!

 

[RSMemphis]

A second picture to the left means that there IS signal reflection, as a previous poster has implied.

It's most likely a cheap switch that causes the reflection.
Decent KVMs cost about $80 when you don't want ghosting.

 

[CSFM]

Rotary KVM switches (or manual switches) are not really a viable option for anyone who requires any sort of quality VGA resolution with no ghosting. You are much better off getting yourself a little 2 port KVM from Belkin (although they are cheap and nasty too) or if you looking for real quality I would say Raritan or Cybex would be you best choice.
I like you ideas on twisting and adding shield to the VGA cable though... but I think the main loss of integrity in the signal is from below par soldering and the type of cable used inside the boxes. I assume your using high grade VGA cable with the KVM switch... I like to always have Tri- coax cable with 10 data wires and 2 ferrite filters on my cables... to be sure to be sure!

 

[Mday]

soybomb, lower your resolution, and you should see better image quality.

other than that, you gotta get a new switch.