A tip about finding the schematics; the ipdb listing for Radical doesn't have much of them with the link marked 'Manual', so try looking at similar age games. I chose Earthshaker.
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Hi, I have tried shorting D3 next to the relay and I don’t hear any click. Pressing flipper button still does nothing with the diode grounded on the plain side. Could it be the drive transistor failed?"
- The basic technique of grounding the return side of a solenoid load (the flipper relay in this case) by-passes the usual control device(s), so it proves nothing directly about them. It only shows if the load/relay itself works, as it seems to have done. If the relay had worked when jumpered but not in play or diagnostic, then I'd suspect the circuitry controlling the relay. If it hadn't worked even when jumpered, then it wouldn't in any circumstance, again showing nothing about the driver circuit.
Though it seems to have cleared up now, the flipper relay isn't controlled by a large metal-framed transistor as with other solenoids. It's simply a small black plastic-bodied device, a 2N4401 (
or maybe its opposite polarity equivalent 4403). And there isn't a dedicated line just for switching the relay; it's basically an addition at the end of the circuitry that enables/disables what Williams used to call 'Special Solenoids', meaning bumpers and slingshots. The wiring for the flipper circuits travels from Aux Power to playfield, then the cabinet buttons and Cpu board through quite a few connectors, including the Interconnect board below the Cpu board.
Work didn't have Bally System 11 machines, but I expect they follow the Williams practice of the button switching two flippers using three contact blades, rather than the older Bally method of a lower flipper switching an upper one. You'll see by looking at the button contacts, or if the lower flippers only have their own End of Stroke switches, with capacitors attached.
I'd like to blame that 'Williams brand only' policy for the fact that it's only checking with ipdb which has taught me that the prototypes had a ball popper exiting onto the left-hand ramp, fed by a subway from somewhere top centre. Eliminated for production, though the flyer even shows a ball flying through the wireform.
One thing in the manual for Radical; the basic drawing showing parts under the playfield has the disliked Bally 'linear' slingshots from the early 80's, while the de**iled assembly drawings show the regular Williams pivot-type fittings.
