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

 

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

 

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.

 

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 ?

 

Ray, Cables in conference rooms take a beating. We get our share of bad

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.

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

 

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.

 

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!

 

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