I have an intermittent, but persistent problem in my Doctor Who that has me scratching my head...

Once every few games, 2 balls will be launched into the shooter lane. It never happens at the start of a new ball. It usually happens after locking the first ball into the Tardis, but sometimes upon ball save as well.

I have replaced the switches in the ball trough, in the shooter lane, and the launch button, to no avail. The switches (even the old ones that were replaced) test perfectly in the switch test, 100% of the time.

Any ideas for things to look at? I’m stumped!

New diode when the switch was installed. Balls were changed recently and are not magnetized. The trough has a cliffy installed, but the problem existed before (and after) the installation of the cliffy.

Bump. Anybody have other ideas?

One gets kicked out, auto launches, and the second ball is kicked into the shooter lane before the first ball has come to rest on the VUK.

3 balls installed, which is correct.

Like I said the switches in the trough, shooter lane, and the launch button are all new-- replaced in an effort to resolve this problem.

I've spent a lot of time tinkering with those switches, but I'll pull the apron again, and tinker more.

MPU is good. No acid damage at all, NVRAM installed by Aardvark about 18 months ago.

They are all on the same column in the switch matrix. I haven't had any problems with the coin door switch or the slam tilt switch, but I should probably take a closer look at J206-2.

doctor who (resized).jpg

The trough switches are mechanical, not optos. Yes, the trough switches open and close as appropriate during switch tests with a ball. I am not able to find any errors during repeated switch tests.

For some reason, I can't edit the post... I'll check the VUK opto. I haven't tested that one yet.

I took a close look with the apron off, and played about 10 games without the problem occurring. First game with the apron back on, it happened again.Arrrggghhh!!!

Hmmm... I’m not sure what it could possibly be on the apron, but I’ll tinker some more tonight.

Oh, and for the record, the drain switch, the three trough switches, the two shooter lane switches and the telephone onto all checked out just fine.

It’s a good theory, but I tested the trough with a single ball, and it registered every time. I *could* move the Cliffy a bit and see if it helps any, but the problem existed before the Cliffy was installed.

I don’t understand- you want a photo of the apron installed, looking into the eject hole?

I think this is the photo you’re asking for...

DAC73675-C854-4A4B-8C43-EA2DB1E2A678 (resized).jpeg

I'll give that a try after work and report back.

But the apron isn't part of that equation, so I'm not sure why the problem goes away when the apron isn't in place.

Bent the ball guide as suggested-- no change.

So Aphex and I tinkered around with it again tonight, and I think we *might* have figured it out. The ball guide that sits horizontally above the outhole had a gap that was significantly smaller than the other WPC games in my collection. We bent that, and played a handful of games without the double launch happening... so we may have stumbled into the solution.

...and... it just did it to both of us in a two player game.

*sigh*

Nope. It doesn't happen often, but maybe once every 10 games it will randomly happen.

I swapped the outhole switches for new ones.

I don't remember if I checked J206-2 or not, but I will (the other poster zombied an almost 2 year old thread of mine). I'll report back.