Replace the TIP42 lamp matrix transistors (Q63, Q65, Q67, Q69, Q71, Q73, Q75, Q77) with 8 x IRF9z34N mosfets.
For positions see: Driver Board Drawing
The Mosfets are installed just like the TIP 42 transistors- they are "pin compatible". The mosfets take a tiny amount of current to drive them,
and so the 27 ohm resistors at R149-R156 never get hot.
Because of this there is no need to replace the 27 ohm resistors -unless you want to change them for new 2-3W ones.
If they are in reasonable condition, just leave the old ones installed. If all the TIP42s are replaced with 8 x Irf9z34n mosfets
the 27 ohm power resistors R149-156 probably can be replaced with jumper wires or zero ohm resistors!
So far everything is perfect in my test FirePower game, the resistors never even get warm.
ALWAYS A GOOD IDEA
2. Use #47 light bulbs for the feature lamps, as this will decrease feature lamp power consumption by about 40%!
Everyone will tell you this is a good idea. It is, and can prolong the life of your backglass as well as the driver board.
YOU COULD ALSO TRY...
3. Adding a 12v PC Fan from a Power supply or PC Case. Blow the air up from underneath towards the 27 ohm resitors.
If fits snugly in the neck at the cutout between the cabinet and the backbox. This seems to work and may "save" a board if the CPU locks up but
the fan stays running. You could even use a PC power supply if you want to avoid connecting the power from your boards.
LAST - AND IN TERMS OF COST, CHEAPEST
4. Replace these eight driver board resistors at R149-R156 with 27 ohm 5 Watt sand or ceramic wire wound resistors. They MUST be 3W at least and preferably 5W
I used to buy them at Maplin when they stocked 5W ones, lately they stock only 27 ohm in 3W, but that's still OK.
Farnell: # 34230; 27R 3W wirewound resistor .44ea + = .37ea
Maplin: # W27R; 27R 3W Wirewound resistor .19ea + = .15ea ?
Also as per the originals, make sure to install the new resistors at 1/4" (.6cm) off the circuit board to allow better air flow around them.
The Best
solutions for your game is to do #1 AND #2. Or to do #2 AND #4
if you want to stay more "original".
SWITCH MATRIX CIRCUIT
While you are making changes, I recommend you replace the 8 x 330 ohm Resistors at connector 2J2. These are numbered R204-R211 on games before Black Knight (System 7).
Replace them with zero ohm reisitors, or even easier is to use wire jumpers. They shown as Blue/White coloured wires on the Top Right of the board below called MOSFET BOARD #1.
Compare this with the same section of MOSFET BOARD #2 where the original resistors are still in place.
I believe this modification lets PIA II sense more than two switches closed at the same time, will improve things for the Switch Column drives. I have had no problems using these"jumpered" boards in Firepower,
if you do experience a problem with a game after this change I would like to know. If anything it should just increase the switch sensitivity, which I expect is a positive change.
SOLENOID DRIVER CIRCUIT
I also worked on how to do a rebuild
on the solenoid section. I have created the Driver "logic diagrams" on a single page, thanks for the comments that this was
needed!
The Original Williams Driver Board has been finished as a vectored drawing in Oct '08
so that the PDF is under 450K and it scales nicely to any size.
The Mosfet Driver Board design is a vectored PDF drawing as well.
Please use the second diagram only if you read and understand the following statements and read all information on this page:
You make any of these modifications at your own risk.
I can not be held responsible for any damage to your pinball boards or games. I only claim "this has worked well for me" and your milage may vary...
This Mod uses MOSFETs to "beef up" the soleniod driver circuits on the Driver boards. I have had a few requests to publish this, so here goes.
The Boards didn't change much between System 4-7, there are some jumpers that can replace resistors on the switch matrix for Sys 7.
This mod replaces BOTH
the TIP120 and the 2N4401 pre-driver transistors on the left hand side of the baord
for the 22 Solenoids. The Lamp Matrix and Switch Matrix are
both unchanged, although you can directly replace TIP42's in the Lamp matrix with MOSFETs. See above.
DON'T EVEN THINK OF DOING THIS UNLESS YOU
HAVE A WORKING DRIVER BOARD TO START WITH.
For
each solenoid (22 in total) you will need:
- a single N-channel MOSFET use the IRL520N (INT'L. RECT.) or I used the MTP10N10EL (ON SEMI)
-
a couple of Diodes in a common cathode configuration, a 47v 1Watt Zener 1N4756A (e.g. Vishay)
a
1n4148 Fast Switching Diode (common part)
- and a 10K ohm resistor 1/4 WATT 5% (common part) That's it.
You remove all the other resistors in these circuits (at e.g. R29. R30 &R31 for Solenoid #1).
You don't need to do all of them at the same time - you can do the solenoids a few at a time
so do a few and then test you got it right.
...BUT...
YOU WILL NEED TO USE 74HCT08 IC chips
(and sockets)
as ICs 1-4 which are for triggering solenoids 1-16,
and
74HCT02 IC chips (and sockets)
for ICs 8 & 9
- these are for the Special Solenoids 1-6
again see:
Driver Board Drawing the chip and Solenoid Transistor positions, and
the logic diagram above to see which ones to replace.
It is possible to replace, for example, only the "Special
Solenoids" 1-6 in which case you just need to have ICs 8 & 9 replaced with 74HCT02.
I HAVE TRIED TO SHOW THIS ON THE LOGIC DIAGRAMS, AND THESE 6 CHIPS NEED TO BE CHANGED FOR THE SOLENOID MOSFET MOD.
The Driver Board diagram is from the UK site: www.firepowerpinball.com
...big kudos goes to Phil Butcher graphic artist without peer.
![[Circuit Drawing]](img/scan-cct-drawing.jpg)
Scan of the original design for solenoid board mod showing my projected parts layout
|
This is cool.
The diode on your solenoid coil can fail open, or even fall off during game play (and this can and does happen due to vibration).
This circuit design should compensate and protect the coil. It also protects the ICs further up
from damage: Like the 7408s and the 6821 PIAs. As you will see I always socket ICs like the PIAs as on my board the old sockets were scanbe and caused problems.
There is less to go wrong once the change is made, because you have one beefy 100v Mosfet instead of the 2 Transistors.
Power Mosfets seem to take a lot of abuse before they fail!
The old games seem more "lively" to me (pop bumpers, kickers, slings) once you put in an updated driver board with the solenoid Mosfets and the switch matrix jumpers.
I've built two prototypes and have this working in a System 6 Firepower and have also tested them with a Sys 7 game, and Sys 4.
You may notice that the second prototype board (#2)used smaller 10K resistors, so the layout was better.
I also added a blanking indicator LED on prototype #2 as Clay mentions- on pin 37 of
the 40 way connector to ground. Use 220 OR 270 Ohm resistor in series.
What's the downside?
Well there is a LOT of work with a soldering iron, although the parts do fit on the original circuit perfectly the way I've laid it out. There is a
cost for the parts, but it's actually not too bad... should be less than GBP 30 in all. This of course depends on the parts sources you have.
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ROMS
Driver Board Repairs and my Mosfet Mod for FirePower (and games that use this driver board)
![[Driver]](img/FP-Parts-Drv.jpg)
![[MOSFET Driver #1]](img/driver-mos-1.jpg)
![[MOSFET Driver #2]](img/driver-mos-2.jpg)
![[MOSFET Driver #2 Closeup]](img/driver-mos-2-cu.jpg)