@GGG posted:(1)... RAW Track signal does go to an opamp to work in conjunction with audio amp to detect offset for bell/horn.
(2)...Regardless, how is it triggering the motor fet and relay with a small offset. From my perspective depending on how fast it moves with the offset signal present the voltage is getting to motor directly.
(3)...So this is all speculation. I would like to see the board to actually observe the actions. G
(1) OK. we'll just have to agree to disagree on this one. I'm suggesting that any DC offsets in the track voltage are detected/measured by the processor chip. The processor chip is the master-of-the-universe such that EVERYTHING goes thru the processor where all decisions are made about what sounds to play (including bell and horn), how to drive the motor, when to flip the relay between Fwd and Rev, etc.
For example, even in conventional mode, when it is working right if you hold the horn button for an extended interval the processor will play an extended tail sound of the horn which is kind of neat. This suggests it is the processor that is measuring the time that DC offset is present and deciding what horn sound to play. Likewise, the processor must be looking at the track voltage (and any DC offset) to decode the Horn-Bell combinations to fire the coupler, activate PFA/PSA, and so on.
(2) Again, we can agree to disagree. I do not see how a track voltage with negative offset (i.e., Bell button pressed) can get thru the bridge rectifier and maintain its negative polarity. That is, a bridge rectifer converts either polarity to "positive" voltage in this case. The ONLY way the engine can go backwards in a PS2 engine is if the processor flips the relay which in effect flips the positive PV voltage to negative essentially right at the motor.
(3) Now this we can agree on. This is all speculation! I would like to see the engine in the hands of a capable tech (like you of course!). Again, if the OP does go this route and the tech chooses to openly discuss on this thread, I will dig up a PS2 board and fire up the scope to elaborate my speculations.
Otherwise, I believe there's an even-odds chance the engine will operate in DCS command mode since measurement of the track voltage is not used. Though there may be an issue with the processor properly detecting loss of track voltage for the purpose of shutting down the engine and performing related shutdown chores (such as saving any changed parameters like the engine address, and finally electrically disconnecting the battery).
