Hi,

On my STTNG the flashers stopped working. I found that LED5 was off, and F111 was blown. After replacing F111, everything worked again - except 1 flasher. Replaced that, and all was well. For about 5-10 minutes, after which fuse F111 blew again. Thinking it could be a bad fuse, I replaced it again. Everything worked OK. I even used the testing menu to test everything: normal lamps, flashers, coils, screen, sound, etc. But again, after 5 - 10 minutes of game time it blew again.

Reading this forum, I concluded there's likely a bad flasher or flasher socket somewhere. To make the investigation easier, I tried to disconnect the backboard flashers by disconnecting J106. There's only a single wire coming from it: J106-5. It is documented as providing "+20V, to backbox flashlamps".

My expectation was that none of the flashers on the backbox would work, while the flashers on the playfield would work normally. (Well, perhaps until F111 would blow again.) What actually happened was that *all* flashers worked normally - the ones on the playfield *and* the ones in the backbox. I entered the testing menu, and basically ran all available tests: I did not notice *any* problem or *any* lamp/flasher not working.

Is it normal that disconnecting J106 does not result in any noticeable difference?

After unplugging both J106 and J107, using a multimeter I discovered that the wire normally connecting to J106-5 and the wire normally connecting to J107-6 seem to be connecting to each other somewhere. I understand from your answer that this should not be the case?

My assumption (based on the Service Manual) was that J106-5 is directly routed to the backboard and not the playfield, while J107-6 is routed to the playfield and not the backboard. I tried to verify this assumption by following the wires without disconnecting any further connectors, but I didn't succeed.

Given the symptoms, the only conclusion I can think of is that J106-5 and J107-6 must be shorted somewhere. It seems that J106-5 is not just wired to the backbox, but also to the playfield. Or did I miss anything?

(I discovered that a pair of probably unrelated wires were directly soldered to the connector pins of the power board, instead of going through a connector. This leads me to think a previous owner performed a somewhat sub-optimal (...) repair, which in turn leads me to suspect the other wiring.)

Thanks! The picture in that post made the pieces of the puzzle fall into place. I'll start hunting for a bad bulb/socket or short to ground.