Compaq V75 Monitor signal cable spliced

Not really a piece of electronic repair work, but it was necessary to read up and work precisely.

The problem with the monitor was that one of the pins in the 15-pin D-Sub connector came loose and moved back into the connector. At first, it was possible to pull the pin out again with a long nose pliers, sometimes wiggling the cable would make the monitor work again. Finally the pin was totally gone and the monitor would not work any more.

I had an old cable from a different make and model monitor. Even if I would be able to buy the correct new cable (not being a Compaq agent), it would probably have been to expensive since the monitor is old. The header plugs, plugging into the PC board inside the monitor, was of course different between the two monitors. Thus I had to cut off that end of both the cables and splice the Compaq header plug onto the other cable.

First I looked up some references on the internet to find the standard SVGA 15-pin plug pinout. I was worried about the monitor ID pins, as they did not seem all present on both cables. After Googling a bit more I found the following here: Q:-I give up: How does a Sony (FX-140) notebook recognize the presence of an external (VGA/SVGA) monitor?...Any hints? Diodes between pins...resistors...holy water? A:- Monitor ID pins haven't been used for a LONG time.
The ID solution used today is a VESA standard called the Display Data Channel (DDC), which is based on the I2C electrical interface.

So I printed one of the Pinout Tables I found on the internet, and on the same piece of paper started making a list of the wires in each cable, by testing them out with a multimeter on diode test, so it will beep on continuity. I used a short cable with crocodile clips and a bent-open staple to connect to the "header" connector, using the free probe on the 15-pin D-sub.


After re-checking each cable again, I took the final step and cut both cables. In the case of the "new" cable, the ferrite core around it used to be inside the monitor, only secured by two cable ties. Remember to slip it over the long cable before you start splicing! As can be seen, a small bench vice (even if not mounted!) makes it a lot easier than holding everything with your hands. I started with the easy ones, e.g. the red, green and blue plus their returns. It is important to try to keep these returns seperate, I think it might not prevent your monitor from working, but it might influence the display quality. As I was joining the wires, I slipped a short piece of small heat-shring sleaving over each wire. Of course a bigger heat-shrink was already slipped over the entire cable.

At this point I tested the monitor with an old computer, making sure the short pieces of sleeving were all in place. The next day I took the cable with me, borrowed a heat gun and shrunk the sleeves. The "new" cable actually had 3 thin coax cables inside it for the RGB. Thus the sleevings could not entirely cover their returns. I used short pieces of insulation tape on them as well. Then I slipped over the big sleeving and shrunk it as well.


This monitor had a bit of an unusual molding where the calbe enters the monitor. I used a knife (carefully!) to cut it open from the outside corner. Thus I was able to insert the new cable into it.


After fitting this extra little cover over it, it does not matter that this corner moulding is cut open.


The ferrite core was now move close to the monitor and again secured with two cable ties. I does not look as smart as a moulded-in one, but being on the back of the monitor it does not bother anyone.

Job done!

I think it is important for the environment to keep things like computer monitors working for as long as possible. When you finally throw it away, it gets destroyed, some of its parts may pollute the earth, you go to the store and buy a new one, a factory somewhere has to make another one to replace the stock. A lot of pollution takes place making the new one. You might say yes, an LCD monitor is not so expensive now, but hopefully the you still have a long life ahead of you to enjoy LCD monitors. Just try to keep he old one a year or two longer, OK?