My Flasher problem

As reported in April, I have a flasher problem, which is proving to be a challenge. It turns out that there are 5 separate flasher “circuits” each with at least two flashers connected in parallel.

The flashers flash by being “turned on” (having 20V applied to them) very briefly. As they’re 12V bulbs they therefore “flash” very brightly. The flashers always have 20V applied to one side of them and the other is left floating (ie not connected), meaning that no current can flow, so that they remain off. However, when turned on, the floating side of the flasher is effectively grounded through a power transistor (TIP102). This power transistor is turned on using a signal transistor (2N5401). Simple.

So now to my problem: when I test the flasher circuits separately using the testing procedure, each circuit flashes as it should. However, when I test all bulbs and flashers simultaneously, the Train/Upper Left Ramp flashers (which are connected)¬†flash very dimly as do the Telephone/Upper Right Ramp flashers. This is also the case during game play. Interestingly though, during game play I’ve noticed that when the Telephone lamp flashes, sometimes the Upper Right Ramp flasher doesn’t appear to flash as brightly. As these two bulbs are connected in parallel, this is very strange.

The two problem flasher circuits are connected to the same pin of J107 on the WPC power board (pin 6), so in theory, it could be, that when all the flashers and lamps are activated, that the 20V supply on this pin is less than the supply on pin 5 (to which all other flasher circuits are connected). However these two pins are connected together on the power board, so that can not be the problem.

To see whether there was a problem with the resistance of these two flasher circuits, I briefly shorted their corresponding pins on J126 to ground (thereby by-passing the “grounding” circuitry) and both flasher circuits flashed as expected. This implies to me, that the problem is actually with the two grounding circuits not grounding completely (although I find this hard to believe).

So I’ve decided to replace the Bridge Rectifier (BR4) which provides the 20V supply to the flasher circuit and its corresponding capacitor (C11) as well as the TIP107 and 2N5401 for both “grounding” circuits.

Hopefully with these updates the supply to the flasher circuits will be good as new!

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