Pole Position steering issue

scottz29

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Donor 2024
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I have a really strange issue with my Pole Position II.

For example...... on the Fuji track when you're full speed, as you approach the hairpin turn, you have to spin the wheel hard left to navigate that bend. No problem. However, on some other tracks, a hard RIGHT turn is required, and at full speed, if you spin the wheel fast enough, it sometimes results in the car barely turning at all, or just going straight!

Steering slowly or moderately to the right works fine. The problem only occurs when you spin the wheel super hard to the right.

In test mode, the data confirms this. Spinning the wheel to the left shows the hex value for the steering pot decreasing at a rapid rate. Spinning the wheel to the right shows the value jumping around, but not increasing as fast as you might expect. In some cases, after you spin the wheel for a second or two, the value might even be less.

Optical encoder wheel is perfectly clean with no bends. Encoder was removed and cleaned.

Anybody have any ideas why a hard right turn would behave less accurately than a hard left turn??
 
a few possibilities to consider:

referring to the schematic Pole Position (SP-218 8th Printing) [Schematic Package] [English].pdf, page 5, start with checking the voltage at the steering coupler pcb (pin 2 accord to the schematic). should be 5v. also the faster the steering wheel moves, the shorter are the pulses from pins 1 & 4 of the steering coupler (optical encoder) pcb ST1 and ST2. hmm.

then next step inward from there is page 16 and the steering inputs into the custom ic 53 at possie 9k. the inputs are r/c circuits with schmidt trigger input inverters (the 4584b IC) following to squareup the resulting steering quadrature signals. check the related components (pullup resistors, and the rc circuit resistors/caps) between ST1 and ST2 and the inputs to the 4584b inverter IC. the pulses may be being stretched too long due to component fault or degradation (change in value) or poor solder joints (ditto) and pulses may be overlapping each other, reducing the number of pulses to be decoded by the custom ic. hence possible poor steering performance at higher steering wheel rotational rates.

also, check that the custom ic 53 (at possie 9k) legs are clean and the socket and solder joints are good.

lastly, you may also have a faulty 4584B schmidt trigger input inverter ic.

interested to know how you go as i am working on a set for a friend here in aus.
 
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