I've been working on a Taxi, and during the coil tests the top right pop bumper doesn't fire, although all the other pop bumpers do fire during the coil test. But when playing the game, the top right bumper works fine. Any idea how this can be?
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Bumper works in game, but not in test mode??
- Thread starter Mfresh
- Start date
Perhaps I’m looking at this differently to you but if it works fine in game play then why bother to find out why it don’t in coil test. Enjoy it cos it’s usually the other way round. 
Taxi's one of Williams' final games with 'Special' switched solenoids, and even then it's only used for the bumpers. The drive pulse from the Cpu is only produced for the coil test - during play the program only finds out about a bumper firing after it's happened, when it sees the additional 'scoring' switch operated by the bumper linkage.
There may be damage to the gating logic for the special solenoids, or the bumper wiring connections may have been altered to drive from the unused Special circuit, assuming Taxi has one. I've heard of such actions being taken, on a Black Knight 2000, to avoid a circuit board repair to a damaged coil transistor.
There may be damage to the gating logic for the special solenoids, or the bumper wiring connections may have been altered to drive from the unused Special circuit, assuming Taxi has one. I've heard of such actions being taken, on a Black Knight 2000, to avoid a circuit board repair to a damaged coil transistor.
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OP
OP
Does that still apply given that the other two bumpers fire in the coil test - it's only the top right that doesn't?
During play, does that bumper score points as it should?
OP
OP
Yes
I'm no expert here, but had a look at the schematics. Pretty fascinating how they've done these "special solenoids"...
On the MPU board you can check for continuity between U41 p19 and U49 p5, and U49 p6 to J18 p2.
If that works, you can try replacing U49.
If that doesn't work, I think you will need to replace U41.
On the MPU board you can check for continuity between U41 p19 and U49 p5, and U49 p6 to J18 p2.
If that works, you can try replacing U49.
If that doesn't work, I think you will need to replace U41.
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As I remember it, each of the six Special drives has a not Or (NOR) gate, with either of its two inputs able to switch the solenoid pre-driver/driver and coil (or sometimes flashbulb load). One input is the 'Special' switch, from a bumper or slingshot, the other is used by the Cpu to switch the solenoid when necessary, e.g during solenoid test or at other times if the drive's being used for a different purpose, such as an eye-socket flash bulb on Pin-Bot, a diverter on F-14 or a ball lock/eject on Space Station.
A by-product of using this method for bumpers and slingshots is that failure of a coil brings up a Test Report of the device's normal, 'matrix' switch, since it isn't operated at all once the problem occurs. Later games with normal drive for bumpers & slings will still see bumper and slingshot switching activity, though reduced. Only one game I've seen, Dr. Who, is programmed to tally the number of hits on each bumper and report if they aren't roughly the same.
The drawback of the arrangement is lock-on of the coil if a Special switch remains closed. A Banzai Run I played once was prone to getting a ball jammed between a bumper and a playfield post, keeping the activating switch closed and blowing a fuse.
A by-product of using this method for bumpers and slingshots is that failure of a coil brings up a Test Report of the device's normal, 'matrix' switch, since it isn't operated at all once the problem occurs. Later games with normal drive for bumpers & slings will still see bumper and slingshot switching activity, though reduced. Only one game I've seen, Dr. Who, is programmed to tally the number of hits on each bumper and report if they aren't roughly the same.
The drawback of the arrangement is lock-on of the coil if a Special switch remains closed. A Banzai Run I played once was prone to getting a ball jammed between a bumper and a playfield post, keeping the activating switch closed and blowing a fuse.