DVI, DFP cabling, Pendant relocation....

Awl --
This is Round 2 of trying to get the screen of that re-located Haas controller to work right (previous thread CNC display problem...).
The extension cable is sort of ok, but iyr, the 35 ft replacement DFP cable really degraded the screen image. Usable, but irksome.
So I ordered DFP to DVI adapters for each board, and figgered I run a DVI cable in between, since they are readily available.
No go. The screen displays NO DATA whatsoever, just full-screen blinking solid colors.
On a lark, I started ohming stuff out. The original haas 13 ft dfp cable ohms out at 0.8 ohms (0.4 on the shield). The 35 ft replacement dfp ohms out at 2.1 (0.3 on the ground).
So the ohm diffs on the dfp cables would explain some of the screen problems, I imagine.
Here's where it gets inneresting.
The DVI cables (the 25' I bought, one I have laying around), well, ohms is more-or-less moot: Half the pins aren't even connected!!!! And the pattern is different between the two DVI's I have!!! Of the ones that did ohm out, the 6 ft cable measured a reasonable 0.3 ohms, while the 25 footer measured a whopping 4.5 ohms!!! DOUBLE the 35 ft dfp cable. I'm surprised the screen even showed colors!!
So my basic Q is: Can I get a DVI cable with ALL 24 pins connected?? Which is a minor problem in itself, as the DFP is 26 pin, so I have to hope that I luck out, connection-wise. I'm pretty sure not all 26 dfp pins are actually utilized, but the unanswerable Q for me is, Which ones?
Ultimately, I may just get a second dfp cable -- or two -- from Haas, and splice them together. Is this actually a better solution than muckymucking around with dvi-dfp adapters, and dicey dvi cables?
I would like to use a fem-fem dfp coupler so I wouldn't have to splice the dfp, but I can't find any online and I don't know much about the type of fem connectors used on the board so I could make a coupler, but I don't know what to search on, or if I'll be able to find those. What would I search on?
Never a dull moment.
--
EA



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If I splice two haas cables together, the ohms will be 1.6. That's getting up near the 2.1 ohms of the 35 footer, so if ohms/impedance is the issue here, I'll have a worse image than the original haas single cable, but better than with the 35 footer. A reasonable conclusion?
Does it make sense to put a booster gadget in the splice? I guess the Q would be, How many wires is it boosting?? Also, I don't want to fry any boards....
Dat splice will proly wind up being the size of a tennis ball.... LOL
--
EA



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On 4/27/2013 21:22, Existential Angst wrote:

What I would do is to get a DFP cable from Haas, cut it to two pieces and look at the wires in the cable. Any coax cables inside? There are special cables with twisted pair, normal wires and coax cables in the same cable. Can you get a wiring diagram? Then wire-by-wire add an extension between the cut ends - making any coaxes or twisted pairs extended with same type cable. This would be the way to go, IMHO.
If you get the wiring diagram, use pieces of coax or such with correct impedance for video signals. The ohms is not really important between ends of wires, but the impedance of the cable. For example, video coax is usually 75ohms. You can't measure that with any simple measurement.
Kristian Ukkonen.
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As I think about it, I am definitely getting another cable (or two) from Haas. Since I'll have to ring everything out anyway, all the wire types and impedances MUST match, and that should be the best solution -- tennis ball-sized splice notwithstanding. Altho with the right shrink tube, mebbe not so bad.
Had I known about this wide variability in pinouts, cable construction, etc., I'da bit the bullet gone the haas splice route from the gitgo. The fly there is that Haas is not easy to deal with. Not spitefully terrible, mind you, just a lot of corporate inertia, left hand/right hand, etc.
Been an expensive and time consuming learning experience.
--
EA


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Heh, I thought the DFP connectors looked just like Centronics connectors, and they are.. although the newer version is micro Centronics.
Yeah.. standards, adapters and conversions = clusterfuck.
Just because Haas (or the board manufacturer) chose DFP connectors doesn't mean the cable is standard for anything else, DVI for TV or PC, for example. I think you mentioned that the power for the pendant is also included in the cable, and I'm guessing some command signal cables that wouldn't be present in TV or other applications.
You should be able to attain micro centronics connectors at the usual places.. DigiKey, Mouser etc, and make the same-gender connections with the shorter Haas cables (no unnecessary cable cutting/splicing). This would most likely provide the best results. Enclose the inline connections to keep the connectors clean and dry. There may be slight mismatch of overall cable impedence at the connectors, but should still be a lot better than the signals being sent over wires of the wrong impedence.
The end-to-end resistance doesn't offer much of a comparison. The important issue is if the proper shielded cables are in the right positions.
Odd that Haas has assumed that all machine installations could be done with one length of cable.
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WB
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