repost from original NLG site.
I should mention before going down this road that ONE computer
power supply can be used to replace both the upper and lower power
supplies. That is covered in another post. But sometimes people
want to do things this way. So for completeness, here's a technique
to show how to replace just the upper power supply.
So we covered replacing the lower main power supply on Williams
Dotmation model 40x slot machines. I figured should probably show
how to fix the upper dotmation power supply.
Yes there are two different power supplies in a Williams model 40x
slot machine. The lower (main) power supply gives +5, +12, -12,
+20 volts for the processor boards. But there is a second power
supply that lives behind the DMD (dot matrix display) box. This power supply
takes 120 volts AC input and puts out 12 volts DC output. This 12 vdc
is fed to the Dot Matrix Controller (DMC) and the DMD. Then both
of these boards take the input 12 vdc and manipulate it as they need.
(For example the DMD turns the 12 volts into +/- 120 volts DC).
The problem with the upper Dotmation power supply is similar to
the lower main power supply, it dies a lot! Though slightly better
than the lower power supply (it only outputs one voltage), it's still
problematic. Repair is definately possible, but replacement seems
to be where most people want to go.
Note that the upper Dotmation power supply and the lower main
power supply are made by the same company, and generally
look the same! That is, don't confuse these two power supplies.
If for example you install the Dotmation power supply mistakenly
in the lower power supply "can", you WILL smoke the I/O board,
processor board, and the meter board. (Please don't ask me
how i know this!)
Original Lower Power supply part#: PU110-31A
Original Dotmation Power supply part#: PU110-12A
Note the connectors are EXACTLY the same for both
power supplies! (though the output voltages are different.)
Though you didn't need to know this for this repair, I thought
it was important to mention it.
Anyway, back to replacing the upper Dotmation power supply.
The current trend is to use a video game switching power
supply. For about $25 this is a decent solution, as these power
supplies are small, cheap, and work well. But frankly you could
make your own linear unregulated power supply with a 120 volt
to 12 volt transformer, a bridge rectifier, and a 10,000 mfd
filter cap. (But most people don't want to do that work.)
The original Dotmation P.S. puts out 12 volts at 9 amps.
The replacement video game P.S. i used only puts out 12 volts
at 4 amps. It works, but i would say really 5 amps should be
a bare minimum output for the new power supply's 12 volts.
I suspect the reason Wms did not use just one power supply for the dotmation
and the rest of the game has to do with RF interference. Anytime you have
a power line that is long, there is potential for RF interference. They need to
have these devices approved, and just didn't want to worry about RF interference.
So having a separate PS right next to the DMD limits the potential RF interference.
Likewise, notice on the lower PS the voltage cable from the PS "metal can" to the backbox
is very short
i've been running these 12 volt 4 amp power supplies for the dotmation
on several machines. i'm not a casino, but they have been running fine
and without any issues. If you look at pinballs like Baywatch (which use
the same dot matrix display), they don't have more than 4amps of 12 volts
running their display. So the 4amps is probably fine (though again, i wouldn't
go any lower).
My Dotmation power supply replacement procedure is shown
in pictures below. It's not a "cut and hack" approach (though
I'm betting most people take that approach.)
The steps are as follows:
Parts:
(10) Molex trifurcon crimp connectors pins #08-52-0113
(2) Extra long Molex male header pins# 10-01-2270
(or 09-62-6104 or 09-52-3102). Cut to length desired.
(1) Molex connector housing part# 09-50-3131 (13 pin)
(1) Molex connector housing part# 09-50-3051 (5 pin)
(1) Molex 156" polarized peg, part# 15-04-0219 for the new 13 pin connector
(1) 75 ohm 1/4 resistor
(5) feet of black 18 guage wire
(3) feet of red 18 gauge wire
(1) foot of white 18 gauge wire
(1) foot of green 18 gauge wire
1. Power off, remove top glass. Then unscrew two
retaining screws on the DMD panel metal "can".
Fold the DMD down and out of the way (or unplug
the DMD completely and set aside).
2. Remove the two connectors from the original dotmation power
supply (one 5 pin, one 13 pin). The original Dotmation p.s.
can be left installed or removed.
3. Make two cables that mate to the original Dotmation
power supply cables removed in step#2 above. These are a
5 pin and 13 pin .156" molex female connector. Use a .156" molex
male header pin as an adaptor between the original cable
connectors and the newly made connector cables.
(Though some people will just cut off the original cables'
connectors, and wire them directly to the new power
supply, personally I prefer to make adaptors and to keep
the original cabling intact.)
Cable layout:
5 pin cable: Use 1 foot each of black, white and green wire.
The white wire will be in the middle (pin #3), and the black
and green wires on the outside. See picture below for hook-up
pin numbers.
13 pin cable: Use three 1 foot lengths of red wire (+12 volts),
and four 1 foot lengths of black wire (ground). See picture
below for hook-up pin numbers.
On the 13 pin housing, only 8 of these pins are used.
Since I had some 8 pin housing laying around, i used
that. But using a 13 pin connectors would be better.
I made the new cabling with the same color wires
as the original cables which they will mate. This makes
connection less confusing to the newbie. (See pictures below.)
On the switching video game power supply, add a
75 ohm 1/4 watt resistor between +5 volts and ground.
Switching P.S. need "load" or they try and shut themselves
down. Adding this resistor (though not always needed) will
prevent this problem, since we aren't using the 5 volt supply.
To "mount" the new switching power supply, I used double-sided
foam tape. Amazingly this works pretty well! Just mount the
new power supply behind the DMD metal "can" on the floor of the
head of the slot machine.
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