The PB4 has higher capacity drivers, same as in the PB6 v1.5, but the drive circuit for the drivers is still lacking, causing the transistors to switch 'slowly' and making them susceptible to overheating. The extra copper under the drive transisitors assists in dissipating the heat, but I have still managed to blow one. Those with keen eyes will see the post-manufacture modification to improve the (obviously poor) original driver design.
PB4 powerbases use 15v power supplies, and 3 series diodes to 'waste' about 2v of that. This places 13v on the track (no load) Once passed through the bridge rectifiers on the car chips, the resulting motor voltage is similar to 12v analogue cars.
Extra RF suppression can be seen, compared with the PB6 devices, which causes a noticable dip in the output signal, especially when under load. The suppression is probably to meet strict European standards.
 PB4, rev B, internal |
Ian Harding, Christchurch, New Zealand