How do I rewire my monitor cable?

Question

Could you tell me how to rewire a new plug on to my monitor, my old one was cut off. I have got my new 15 pin plug but need colour codes for pins. It is 8 core cable. Thank you, Brian

Answer

This question was answered on February 12, 2002. Much of the information contained herein may have changed since posting.

Not sure actually what type of monitor you have, towards the end of this segment, there is also a guide to wire an HP monitor I hope this will solve your problem I received this information from the website: www.repairfaq.org/REPAIR

Obviously, this is best done with a schematic However, since such a luxury may not be possible, how can you go about figuring out where all the wires go? Easy answer - very carefully.

For the following, I assume a VGA/SVGA monitor You need to identify the grounds, video signals, H and V sync, and monitor sense lines The procedure is described with respect to a cut cable but if you are trying to identify an unknown connector type on the monitor, the same comments apply to the wiring **inside** the monitor.

First identify the grounds Use an ohmmeter between each wire and the shell of the video connector on the monitor Resistance will be less than an ohm for the ground wires These will often be colored black The shields of the RGB coaxes will also be connected to ground.

The high bandwidth video signals will always use individual coaxial cables These may even be color coded red, green, and blue If not, you can determine which is which later on If there are only three such coaxes, they are the video signals If there are four, the extra one may be the H sync If there are five, the extra two may be the H and V syncs Testing between these wires and ground with an ohmmeter should measure 75 ohms for the video terminations.

Display a lively screen on your PC at a resolution you know the monitor should support (remember, trying to drive a monitor of unknown scan rate specifications beyond its ratings is like playing Russian Roulette.)When in doubt, VGA (640x480, 31.4 KHz H, 60 Hz V) should be safe.

Turn up the brightness and contrast on the monitor If you are lucky,

even without any sync, there will be a visible raster Set it to be just visible If there is none, then it should appear once there is valid sync.

You will need to bring out wires from the video connector on your PC.

Connect the ground of your video card to the ground wires you already

identified on the monitor cable.

Attach a wire in series with a 200-500 ohm resistor to H sync (pin 13)

on the VGA connector.

Momentarily touch the end of this wire to each of the remaining

unidentified wires (including the coaxes if you have 4 or 5 of these and it is not obvious which are the video signals) on the monitor When you find the H sync input, the raster should lock in and probably brighten up If the monitor was originally whining due to lack of sync, it should quiet down.

Once you have located H sync, you can remove the resistor and connect the wire up directly.

Now, attach the video signals It is likely that you will now have a

picture but it will be rolling on the screen Some monitors, however,

will not unblank until they receive both valid H and V sync Use your

resistor with the V sync output of the video card (Pin 14) on the remaining unidentified wires Once you find the V sync input, the display should lock in solid.

The only remaining unknowns are the monitor sense lines For older monitors - those without the ACCESS.bus interface, you can just wire up the sense lines to the appropriate levels (Color: ID0 (Pin 11) to ground, ID1 (Pin 12) NC).

See the document "Pinouts for various connectors in Real Life(tm)" for

detailed hookup information" Replacement VGA connectors are readily

available.

Also see the section: "Replacing the cable on an HP D1182A monitor" for some hints and helpful 'hassle savers(tm)'.

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13.40) Replacing monitor cables or connectors

Many intermittent or erratic loss of color or loss of sync problems are due to a bad cable - more specifically, bad connections usually between the male pins and the wires Or, perhaps, one or more pins were accidentally broken off as a result of the connector being forced in the wrong way around.

Unfortunately, it is all too likely - particularly with newer monitors - that the shell is molded on and impossible to non-destructively remove to access the connector for wire repair or pin replacement.

You have several options:

* For name brand monitors, entire replacement cables may be available These will be pricey ($25 to $50 typical) but are by far the easiest solution.

* The connector itself can be replaced Places like MCM Electronics stock VGA (HD15) male connectors and pins These may be either solder or crimp type (both can actually be soldered if you work at it) It takes a steady hand, bright light, and patience to solder the fine wires to the tiny pins.

A crimp tool is probably not worth the investment for a single repair.

* If you can locate a dead monitor with a good VGA cable still attached, it is possible to cut and splice the wires away from the connector Use an ohmmeter to identify which signal pin connects to which color coded wire on each cable and then solder and tape the individual wires It won't be pretty but should work reasonable well.

Replacing the cable on an HP D1182A monitor

(From: Marion D Kitchens ([email protected])).

By following the procedure in the section: "Identifying connections on unknown or cut monitor cables", I was able to get a D-15 correctly connected on the ends of an HP D1182A monitor's video cable This was a monitor that came to me with the D-15 missing The only remaining unknown is the brown wire but the monitor seems to work fine without it (however, see below).

Cable Wire Internal Pin # Function Resistance D-15 Pin Notes

----------------------------------------------------------------------

White Coax 5,4 Red Video 75 1,6 shield is 6

Black Coax 3,1 Green Video 75 2,7 shield is 7

Red Coax 7,6 Blue Video 75 3,8 shield is 8

Red 8 Gnd 0 10 red & blue are

Blue 9 V sync 1K 14 twisted pair

Yellow 10 Gnd 0 10 yellow & clear are

Clear 11 H Sync 500 13 twisted pair

Brown 12 ID0?? Infinite 11?? Works OK w/o

Internal pin numbers refer to a 12 pin, in-line connector inside the monitor It is mounted on a circuit board (model XC-1429U printed on board) that is mounted on the neck of the CTR There are 12 pins, but one is blank -- nothing connected I have called that one pin # 2 for reference, and the pin furthermost away I called pin #12 Double numbers mean the first is connected to the coax center conductor, and the second is the coax shield.

The double numbered pins under D-15 above mean connect the center conductor of the coax to the first pin number, and the coax shield to the second pin number All the coax shields should measure zero Ohms to ground, and all the center conductors should measure about 75 Ohms to ground Ground is the outer shield of the video cable, which is connected to the D-15 connector shell when doing the wiring job.

Pins 5 & 10 are also listed as ground connections on the D-15 connector I suspect these are for the H sync & V sync, but do not know that for a fact I connected what I believe to be both ground returns (per the twisted pairs show above) to pin 10.

The currently unconnected brown wire does have a signal of some sort on it At least when trying to find the H sync and V sync wires, I got screen reactions if I connected it to some pins on the D-15 connector Since it was the only "left over" wire when I got H sync & V sync correct, I suspect it to be the ID0 wire Yes? No? Maybe? Nothing seems to happen when I connect it to D-15 pin #11 The monitor SEEMS to be OK without the brown wire connected to anything (but the color balance is a bit off, green and blue OK,

but red is a pale pink) An Ohmmeter connected between ground and the brown wire "acts like" it is charging a capacitor -- resistance starts low and increases with time to several 10's of Meg Is that a clue?

As an aid in finding the correct wiring connections I make a special floppy It is a bootable floppy for use in the A: drive Boot the computer from that floppy First format a system floppy for the A: drive Then copy the ANSI.SYS file from your C:\DOS\ files to the floppy Next write a CONGIF.SYS file to the floppy, containing one line --- DEVICE=A:\ANSI.SYS Now write three batch files to the floppy, one for each color.

RED.BAT file

PROMPT $p$g$e[41m

CLS

GREEN.BAT

PROMPT $p$g$e[42m

CLS

BLUE.BAT

PROMPT $p$g$e[44m

CLS

In trying to find the H sync and V sync, I found it most helpful to use the following procedure.

1 Connect all of the ground wires, and one of the coax center conductors (any one at random) to D-15 pin #1.

2 Boot the computer from the above floppy Watch the drive light to

determine when the boot process is completed Hit RETURN twice to get past the new time and date that it asks for.

3 Turn on the monitor, and type RED to run the red batch file.

4 Now follow the procedure in the section: "Identifying connections on unknown or cut monitor cables" to find the H & V sync wires When you have them correct you should see a colored screen (it might be red, green, or blue) and two "A:>" prompts on screen Make sure the brightness control is set for maximum brightness, and that contrast is high.

5 Once you have a readable screen, find the correct coax to produce a red screen when connected to D-15 pin #1 Then type GREEN to run the green batch file, and find the correct coax to produce a green screen The remaining coax is, of course, the blue video But verify that anyway by typing BLUE to run the blue batch file.

6 Now you should be able to get red, green, and blue screens buy running the respective batch files.

To aid in the trial and error process of finding all the correct wiring, I made a small (3 by 4 inch) PCB with 15 connection points and a large grounding point, and mounted a D-15 connector on one edge The 15 copper traces were wired to the D-15 connector so that pin numbers 1 through 15 followed a simple series across one edge of the PCB The 15 traces were about 1/4 by 1 inch to make life easy I even soldered 220 Ohm resistors to pin numbers 13 & 14 on the board to make that easy too With this "aid" I used a video extension

cable to bring my working point to the front of the test bench, and had plenty of working room for all those trial and error connections

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Posted by Teri of Data Doctors on February 12, 2002