REPLACING THE POWER SWITCH ON A COMMODORE MONITOR 2-28-06.


            REPLACING THE POWER SWITCH ON A COMMODORE MONITOR
               Latest updates and corrections: 2-28-06


The standard CBM 1084 series and 1902A monitors made by Philips 
have a separate power supply board mounted on a slide-in plastic tray. 
The power switch is fastened with two screws to the front end of that 
tray so it sits just behind the front panel push button assembly. Four 
wires connect the switch to the chassis. Note the position of the color 
coded wires and install them the same way on the new switch. View how 
it looks before and after switch replacement at 
http://staff.washington.edu/rrcc/uwweb/pics/1084.jpg
     Position the monitor face down on a cloth or newspaper to prevent 
scratches on the front panel. Five screws must be removed to pull the 
rear cover off the monitor. Disconnect the speaker plug from the center 
upright sub-board as you remove the rear cover. To remove the PS tray 
from the cabinet, unplug two connectors on the PS board and unsolder 
the two braided ground straps from the bottom metal shield. One other 
braided strap connects the PS board to the CRT board, and that one may 
need to be removed to be able to pull the tray all the way rearward 
and out. The release for the tray is inside the square cutout 
underneath. Push the release in slightly with a small screwdriver as 
you pull the tray rearward. 
     The mounting holes of the replacement switch may be misaligned 
with the holes in the plastic tray by a fraction of an inch. If so, 
the holes in the tray may be trimmed (elongated) slightly with a thin 
sharp knife so the switch will fit. Although the new switch is 
designed for machine screws, the original self-tap screws will work 
fine. Once the wires are soldered, the tray may be pushed back into 
its slot. You may have to dress the wiring out of the way if it snags 
or binds. Resolder the three shield braids to their previous places 
and reconnect the two plugs to the PS board. Try the switch a few 
times to make sure it latches and unlatches properly before putting 
the rear cover back on. As you reattach the cover, don't forget to 
reconnect the speaker plug. 

     The CBM 1902 and 2002 monitors were made by Fujitsu and have a 
different layout for the power switch than a 1084. It mounts directly 
to the front panel and uses only two wires. Place the monitor face 
down on a cloth. Six screws must be removed to pull the rear cover 
off the monitor. Raise the cover slightly and disconnect the speaker 
plug by squeezing/pulling the connector, then remove the cover. Note 
how the original power switch is mounted and how the wires are 
connected with a small PC board. That board can be discarded along 
with the switch and the two wires soldered directly to two terminals 
of the new switch. The other two terminals of the switch are unused.
     The original installation didn't use the switch mounting holes 
but just two large washers as clamps at the edges of the switch. The 
new switch can be mounted in a similar fashion. However, a slightly 
longer switch actuator may not allow it to release properly when 
turned off. If so, you can use extra washers underneath the edges as 
spacers or you can trim a small amount off the end of the switch 
shaft, no more than 1/8". Observe view before & after the switch 
replacement: http://staff.washington.edu/rrcc/uwweb/pics/1902.jpg. 

     The CBM (Amiga) 1080 uses a completely different chassis made by 
Toshiba. The power switch mounts on the front panel, similar to the 
1902 and 2002 versions. The small PC board must be left in place as 
it also connects to the front panel power indicator LEDs. However, 
the two switch wires may be cut off and soldered directly to two 
terminals of the new switch. As before, you can use a few washers as 
shims if the switch actuator is too long and it doesn't release all 
the way when turned off. An alternative would be to trim no more than 
1/8" off the end of the switch shaft. Note that only two switch 
terminals are used. View the 1902.jpg image  as it is 
similar to this monitor.

     Replacement switches are presently available from two sources. 
These two outlets have no minimum order requirements and you can 
order online, but shipping will exceed the cost of the part unless 
you order more from them. Shipping is by weight and UPS ground is 
the cheapest within the USA.
     Jameco Electronics (www.jameco.com) switch part numbers are 
174238PS ($0.85) and 127049PS ($1.95) as of this writing. The 
switches are identical except the former has small solder terminals 
and the latter has large spade lugs for press-on connectors. 
However, those lugs can be soldered to just as easily. Note that 
the length of the switch actuator shaft is almost 1/8" longer than 
the Commodore original. It can be trimmed or washers can be used as 
spacers to give the new switch adequate clearance. Otherwise the 
switch may not release far enough to turn off. That may or may not 
be a problem as it depends on the exact model and cabinet type. 
     MCM Electronics (www.mcminone.com) part number is SW00450 and 
it costs $3.11 as of this writing. That switch is a closer physical
match to the Commodore original (no trimming or spacers needed) 
but it costs more than the Jameco switches. 
     

 

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