Replacing a faulty signal lead


W

Wayne Atkinson

I've been given a nice Compaq V900 monitor, but it has an intermittent fault
which I've traced to a broken wire in the signal cable.This break is close
to the point of insertion into the monitor near the "choke"? that surrounds
each end of the cable. I've got an "electrical" background and a decent
soldering station, so can anyone say if it's a difficult job to replace the
cable, and how necessary is the choke, i.e.., can I cut it off and re-join
the same (shortened) cable?
Thanks,
Wayne
 
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N

Not Gimpy Anymore

Wayne Atkinson said:
I've been given a nice Compaq V900 monitor, but it has an intermittent
fault which I've traced to a broken wire in the signal cable.This break is
close to the point of insertion into the monitor near the "choke"? that
surrounds each end of the cable. I've got an "electrical" background and a
decent soldering station, so can anyone say if it's a difficult job to
replace the cable, and how necessary is the choke, i.e.., can I cut it off
and re-join the same (shortened) cable?
Thanks,
Wayne
The choke is there for compliance to the FCC radiated emissions
requirements. You can "safely" remove it, but you may experience undesired
interference in other communications devices such as radios, televisions,
and/or phones, etc. If you have close neighbors, they might also experience
same, and if they get irate enough, they have the power to sic the agency on
you, though that's a highly unlikely possibility.
The worse deal will be if you try to "cut & paste" the coax cables that
carry the RGB video signals. The impedance discontinuity is likely to cause
reflections on the cable, which may show up as ghosting of fine details,
generally to the right of the main detail (like a character, or vertical
line). This will be more likely if you are running a larger pixel format and
high refresh rate - to the point where the "cable transit time" is longer
than the "pixel time". In VGA it's not likely to be visible unless the
discontinuity is quite large.
The other option is to try & replace the entire cable, which means
opening up the unit, soldering inside, etc. If the exact cable can be found,
it may be more a job of pluging in pins than soldering, but it can be a real
challenge to try and discover the exact cable (Anybody got a DEAD V900 they
want to give away??).

Several options - none of them very nice, sorry to say.

HTH,
NGA
 
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W

Wayne Atkinson

Thanks very much for the detailed, concise and helpful reply. I've been away
for a short while, hence the delay in saying "thanks". This is beginning to
look like a case of swallowing hard and taking the monitor to the recycling
dept! Pity as the picture was way better than any 19" I've had. I'll try to
locate a replacement cable but I guess I'll have to dig deep and buy a new
monitor. Thanks again and best wishes,
Wayne.
 

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