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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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VGA cable open?
VGA cable fault - solved
We have more than 100 classrooms with ceiling mounted data/video projectors. One room recently had a problem with the projector not "seeing" the computer. In autosearch, it would flash an image for a fraction of a second, then continue searching. Hmmm. Bad sync. Bypassing the VGA cable made it work, so we were down to either repairing the existing cable or pulling another through the conduit... not fun and very time consuming. We usually try for a repair to get a room operational ASAP, but how do you find a break in a cable? Most of it is in the wall and not likely to be damaged or faulty from the factory which should have shown up right away. All I had with me for troubleshooting was my toolkit and o'scope. Cables usually break at the connectors, so I had two choices... the user end or the projector end. Wiggling it at either end didn't make it work with signal on it. Hmmmm. What to do? A TDR would be nice. Perhaps cable capacitance could provide a clue. I scrounged a 47K resistor out of my toolbox and hung one end on the scope calibrator (half a volt 1kHz square wave) and attached the probe to the other end: a quickie low-value cap checker. The scope ground was attached to the cable shell and pins probed with the scope/resistor combination via a jumper lead at each end of the cable. Each used pin showed some capacitance indicated by a rounding off the edges of the square wave... all but the one that broke inside the connector. Pin 13, a sync line, was open at the projector end! Back to the shop for a replacement connector and the room is again operational. R&Ring VGA connectors is no piece of cake, but pulling a new cable is a lot worse. The original was likely damaged by too hard a pull. Ray Carlsen University of Washington, Seattle -- My return addy is spamblocked. To reply, remove the zeroes. |
#2
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VGA cable open?
"Ray" wrote in message ... R&Ring VGA connectors is no piece of cake, You can say that again. Ever tried it on a heavy duty cable like on a Sony 20SF monitor? Fantastic fun, much easier to transplant a cable form a duff monitor in that situation, or buy a 5 BNC to 15 pin DSUB, cut the BNCs off and fit the cable inside the monitor. I sympathise with you having to fit a new plug. Dave |
#3
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VGA cable open?
"Ray" wrote in message ... VGA cable fault - solved We have more than 100 classrooms with ceiling mounted data/video projectors. One room recently had a problem with the projector not "seeing" the computer. In autosearch, it would flash an image for a fraction of a second, then continue searching. Hmmm. Bad sync. Bypassing the VGA cable made it work, so we were down to either repairing the existing cable or pulling another through the conduit... not fun and very time consuming. We usually try for a repair to get a room operational ASAP, but how do you find a break in a cable? Most of it is in the wall and not likely to be damaged or faulty from the factory which should have shown up right away. All I had with me for troubleshooting was my toolkit and o'scope. Cables usually break at the connectors, so I had two choices... the user end or the projector end. Wiggling it at either end didn't make it work with signal on it. Hmmmm. What to do? A TDR would be nice. Perhaps cable capacitance could provide a clue. I scrounged a 47K resistor out of my toolbox and hung one end on the scope calibrator (half a volt 1kHz square wave) and attached the probe to the other end: a quickie low-value cap checker. The scope ground was attached to the cable shell and pins probed with the scope/resistor combination via a jumper lead at each end of the cable. Each used pin showed some capacitance indicated by a rounding off the edges of the square wave... all but the one that broke inside the connector. Pin 13, a sync line, was open at the projector end! Back to the shop for a replacement connector and the room is again operational. R&Ring VGA connectors is no piece of cake, but pulling a new cable is a lot worse. The original was likely damaged by too hard a pull. Good job! I guess I hadn't seen replacement VGA connectors. I would have had to splice a short piece of cable with a connector already attached. Messy, and perhaps not exactly up to standards, but hey! Lynn |
#4
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VGA cable open?
Good job! I guess I hadn't seen replacement VGA connectors. I would have had to splice a short piece of cable with a connector already attached. Messy, and perhaps not exactly up to standards, but hey! Lynn Radio Shack at least used to sell them, HD-15 connectors. I replaced one once on a monitor, it was a royal pain but it worked. |
#5
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VGA cable open?
Ray, Cables in conference rooms take a beating. We get our share of bad
cables and bulbs. We have breakout boxes on the conference tables with short VGA cables plugged into them. Replacing a 4 foot on the table versus pulling new cables tgrough conduit. The cables on the table take a beating. Some rooms go through 2-3 cables a year. We don't seem to get the rated hours out of some projector bulbs. Some seem to make the 2000 hours but some less. We can't pin it down to any make / model. How do you find the life of these expensive bulbs ? |
#6
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VGA cable open?
Ray, Cables in conference rooms take a beating. We get our share of bad
cables and bulbs. We have breakout boxes on the conference tables with short VGA cables plugged into them. Replacing a 4 foot on the table versus pulling new cables tgrough conduit. The cables on the table take a beating. Some rooms go through 2-3 cables a year. Yep, same thing here. We attach "shortie" cables to the fixed ones with gender adaptors so the instructors can't booger up the hard-to-replace ones in the wall. I've seen three failed Calrad brand molded VGA cables recently... either a bad run or just cheap construction. NO more of those. We don't seem to get the rated hours out of some projector bulbs. Some seem to make the 2000 hours but some less. We can't pin it down to any make / model. How do you find the life of these expensive bulbs ? It varies quite a bit and we can't tell the worst offenders ahead of time either. Some projectors sit in rooms that are open to outside air and suck a lot of dust into their tiny filters. Those (Proxima DP9295 is one) need to be cleaned every two weeks or so. The occasional lamp explosion doesn't seem to repeat with a new lamp, so I must assume it's just a random failure. They push those lamps pretty hard and some are just not up to it while others of the same type still work fine at end-of-life. We can't predict how long they will last. I have to say that the majority of ours do make it to their rated hours. Ray -- My return addy is spamblocked. To reply, remove the zeroes. |
#7
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VGA cable open?
Ray,Thanks for the reply. We are finding similar problems ! Ever seen a
brilliant person try plugging in the VGA connector (D shaped) backwards ? They get it done too, amazing what it does to the pins ! Sometimes we starighten out the pins and it works. We do the gender adapter too ! We have some projectors that require a filter cleaning every 150 hours. It's a pain keeping up with them as they need a filter reset as the lamps do. We have some people that keep resetting the lamp timers until it won't fire anymore or the lamp "blows". The filter message requiring the cleaning / reset is a good idea but those units never seem to have dirty filters ! We have some units that the filters get clogged and overheat / shutdown. We can't figure that one out either as some areas / models seem to clog sooner than others. We seem to get the life out of most bulbs but some just don't make it. We gave up trying to get warranty replacement on defective bulbs, suppliers just don't believe they fail before the service life or figure we are pulling a fast one. We have seen at least 5 bulbs premature fail in the 2-3 years we have been servicing these dataprojectors. |
#8
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VGA cable open?
I do a similar short cable when installing projectors, We run the cable in
PVC Trunking and then use a 12" pigtail to the outlet box, I have seen a few bad connectors but I find no problem in soldering new ends on...compared to the 50pin d-ways we use to solder on Cheque sorting machines its easy. Crimping is probably the easiest way to go As for the over heating lamps, how are the projectors mounted? I have seen some with mounting plates blocking air vents. Some projectors also have different fan settings so you can have it running quiet (hot). I always set them to run noisy! "carneyke" wrote in message oups.com... Ray,Thanks for the reply. We are finding similar problems ! Ever seen a brilliant person try plugging in the VGA connector (D shaped) backwards ? They get it done too, amazing what it does to the pins ! Sometimes we starighten out the pins and it works. We do the gender adapter too ! We have some projectors that require a filter cleaning every 150 hours. It's a pain keeping up with them as they need a filter reset as the lamps do. We have some people that keep resetting the lamp timers until it won't fire anymore or the lamp "blows". The filter message requiring the cleaning / reset is a good idea but those units never seem to have dirty filters ! We have some units that the filters get clogged and overheat / shutdown. We can't figure that one out either as some areas / models seem to clog sooner than others. We seem to get the life out of most bulbs but some just don't make it. We gave up trying to get warranty replacement on defective bulbs, suppliers just don't believe they fail before the service life or figure we are pulling a fast one. We have seen at least 5 bulbs premature fail in the 2-3 years we have been servicing these dataprojectors. |
#9
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VGA cable open?
They overheated due to dirty filters. We have more projectors than we
can service. They don't get the filters cleaned because we can't get to them. So, the run until they stop ! Take Care |
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