Replacing a Phillips monitor power switch (1902A, 1084)

[jasonsbeer]

A common issue with Commodore branded Phillips monitors (1902A, 1084, and probably others) is the power switch will inevitably stop latching in the closed position. This prevents your monitor from staying on without holding the power switch in. Unfortunately, the original power switch (PREH TV3 or similar) are no longer manufactured and are expensive, if you can find one. Here is a procedure for replacing the factory switch with one currently available off the shelf. This applies to power switches that are not PCB mounted. Of course, there are dangerous voltages inside the monitor. Be sure it is discharged before attempting repair.

The new switch is labeled KDC-A04 and is a dual pole, single throw (DPST) latching pushbutton switch. It is available for a few dollars from Ebay and other hobby electronics stores.

Here is where I got mine: https://www.ebay.com/itm/2-Pack-Repl...72.m2749.l2649





1) Remove the back of the monitor. As you remove the back, be sure to unplug the speaker cable.



2) The switch is mounted on a bracket with the power supply on the left (from back) side of the monitor. This bracket can be removed to get at the power switch. To remove the board, desolder the grounding wires, as shown in the photos. Remove the grounding plug and the power cable plug, both of which go to other parts of the monitor assembly.











3) Press the black tab under the monitor and slide the board toward the back of the monitor to remove.



4) Desolder and remove the old power switch. Note the orientation of the wires before desoldering.



5) The mounting screws of the original switch are 17mm apart. The mounting holes of the new switch are 20mm. You will need to widen one of the holes to accomodate the difference. One side of the mounting flange is wider than the other. I recommend you shave some plastic from the wider end to ensure a sufficient amount of plastic is left to support the switch. The plastic is soft. Use a 1/8" drill bit by rotating it by hand while pushing in the direction you wish to remove plastic. Remove just enough to ensure the holes easily align with the new switch. The goal is to have an elongated hole. Do not simply make the hole bigger by using a large drill bit. You will remove to much plastic.





6) The new switch must be mounted with the terminals towards the bottom of the monitor. However, two of the termininals must be bent up to clear the plastic bracket on which it is mounted. In addition, I used a grinder to shorten one of the terminals to provide some extra clearance. Otherwise, it would drag on the monitor body where the mounting bracket slides.



7) Mount the new switch and solder the wires in place. I needed an extra inch of cable in order to reach the new switch. I removed the power cable from the strain relief and repositioned it to provide the extra cable.





8) Reverse the disassembly instructions to reassemble. Test fit the new switch and ensure it functions before closing the monitor up.

[Franchute13]

Hi.
Thank for the tutorial. Very good pictures!.

[Jope]

I also swapped these switches in back in the day. Much more robust than the Preh switch and there was always plenty floating around from scrapped PCs I got for free. :-)

[fxgogo]

Nice find.

[Digital Man]

Nice! I have a Magnavox with the same issue. I'll have to bookmark this one.