Opto problems NGG

[Mamushka]

So I noticed one of the gophers (think trolls in MM) in my new to me NGG was up when he shouldn't be. I am using the "This Old Pinball" repair guides to troubleshoot. Here is where I'm at:

• Checked the gopher up/down opto switch for function. It was not working, the other gopher switch works as intended.
• Verified transmitter is working and receiver output changes from ~11V to ~0.5V when triggering the opto. These voltages are consistent with other working opto's
• Checked the switch matrix, all switches in the column are good and all but 1 other switches in the row work. The other non working switch is the only other opto in this row, its voltages are the same as all other opto's. They are both in the middle of the row so there are working switches before and after these switches (believe this rules out a broken switch matrix wire).

So at this point it looks like the opto's are functioning as intended. The guide indicates if this is the case to replace all the LM339 chips on the opto board.

So my question is: Should there be anything else I should check before I order parts and start board work?

[Mamushka]

I was looking to order parts and didn't know if the chips were socketed or not. When I lifted the playfield to look at the board I saw they did have sockets (there are 5 of these chips on the board). I decided to pull the board and see if the problem moved. Swapped the chips and put the board back in and sure enough Buzz now registers up and down. I checked most of the other switches and everything looked good. Played a couple of games and did not notice any problems.

So my thoughts are:

• A chip or connector had a flaky connection that was corrected when they were removed and reinserted.
• I moved the bad chip to a place where it has no impact or I have not noticed the new problem yet.
• Witchcraft.

Regardless, it appears NGG is back to 100% 

[k7]

I was looking to order parts and didn't know if the chips were socketed or not. When I lifted the playfield to look at the board I saw they did have sockets (there are 5 of these chips on the board). I decided to pull the board and see if the problem moved. Swapped the chips and put the board back in and sure enough Buzz now registers up and down. I checked most of the other switches and everything looked good. Played a couple of games and did not notice any problems.

So my thoughts are:

       A chip or connector had a flaky connection that was corrected when they were removed and reinserted.
       I moved the bad chip to a place where it has no impact or I have not noticed the new problem yet.
       Witchcraft...

Regardless, it appears NGG is back to 100% 

100% witchcraft

[FUNWIZ]

The ghost in the machine. What will he do next?

[Mamushka]

The ghost in the machine. What will he do next?

It's not a ghost, it's them damn gophers. 

[hawknole]

Gophers or gremlins.

[NaplesPinball]

I liked almost everything about Gophers.. Except odd opto and Gopher issues.

[djude]

I've noticed the gophers chew on the wires a lot on my NGG...

[Richie107]

I have a bad opto on my Southpark pin in front of Kenny. It doesn't seem to affect the game so I didn't bother with it.. Dunno how critical it is for NGG

[Mamushka]

I have a bad opto on my Southpark pin in front of Kenny. It doesn't seem to affect the game so I didn't bother with it.. Dunno how critical it is for NGG

With this opto it pretty much made the game unplayable. The gophers pop up and down continually through the game to taunt you. They are located at ramp entrances and when they pop up they lift the ramp entrance. Depending on what is going on the gopher and ramp may go down (allowing you to make the ramp) or the ramp may stay up when the gopher drops reviling a tunnel where you can shoot the ball.

For my issue the game always read the gopher was down, so he would pop up, the game saw him as down so it would not trigger to lower him. He then blocked the ramp/tunnel shot.