Got an issue with my STTNG that has stumped me and stumped the repair tech I call in when I'm stumped. Long post...but I wanna give you all the details.
My drop target was not working well--wouldn't always drop when it should, and it turned out to have a piece broken off the reset assembly. I ordered a brand new, assembled drop target assembly from Pinball Life. I installed the assembly myself and, when I switched the game on, the right flippers engaged and blew F103. Figuring I might have done something wrong, I called in my expert.
He re-soldered all the connections, replaced the fuse, tested the solenoids, and replaced the 8-Driver Board with a new Rottendog board (in case I had blown transistors). Solenoids all test fine. Drop target up and down work. The switch functions as it should. The positioning of the target is flush with the playfield when down and doesn't catch.
Now, when starting a game, selecting Lock on ball launch locks the first ball. The target pops up as it should...but, when the next ball is auto-launched, the drop target tries to pop up a few more times, then drops. The next ball then locks. Repeat. Ball 3 locks. Multiball ensues.
Here's what we've tried so far:
* Checked the voltage on the UR 12 volt--just under 14 (about 13.6-13.9). I have a color DMD, but even with the DMD unplugged there's no significant change.
*Swapped the original 8-Driver Board back in. No effect. (I didn't blow transistors after all.)
* Checked all the optos. Found one trough opto out and replaced both trough opto boards with new ones. No effect (other than that all 7 trough switches now work).
* Fixed a sticky kicker in the Borg ship. No effect (other than that it doesn't stick anymore).
* For good measure, we even rebuilt the connectors at the bottom of the MPU board which showed some old acid damage (the MPU board itself was replaced with a Rottendog board with NVRAM).
The only other weird thing we've seen is that occasionally the Borg Lock opto (Switch 31) blinks in test when it shouldn't but it's infrequent, and wiggling the wires etc. doesn't trigger it. Tests fine when manually activated.
So, here we are. We're stumped. Any suggestions what to try next?