Hi All,

I would appreciate if someone with more experience could validate my thinking... =)

I have had some issues with the Disaster drop main switch (c7/r5) randomly triggering during gameplay. Working through the switch matrix I have found that when the Right Trough switch is triggered (c7/r6), if I activate the Left Ramp Main opto (c6/r6) this also activates Disaster drop main switch (c7/r5).

I have desoldered and confirmed that the diode is working on the Right Trough switch and I have completely replaced the Disaster drop main switch and diode. I also know that there's a potential issue with the opto board, considering that it's the Left Ramp main opto that triggers the Disaster drop main switch. But, this only occurs when the Right trough switch is triggered. In the switch test, everything works, including the Left Ramp main opto as long as I don't also trigger the Right trough switch...

Is there any way I can confirm that the issue lies with the opto board? Or do I just have to buy some LM339s and replace on the board as next step? What makes the issue worse is that it's intermittent. I can play the games for hours with no issue, then all of a sudden, the disaster drop switch randomly engages again.
Thanks!

/Stefan

Ah, yeah, just had a look and I'm not that lucky.. mine are straight on the board. Well.. I guess it's time to put some sockets in now. =)

Ah, excellent troubleshooting info, thanks! I have ordered sockets and a bunch of LM339 chips. Should arrive nxt week.. will provide an update once replaced. =)

Ok.. so thought I solved this by buying a new Opto board (with sockets for the LM339 chips). The game worked as soon as I changed the opto board. But, a week later the same issue happened. I had some spare LM339 chips and once replaced, the game was working again. For a single day. After a day the issue is back I'm certain that it's an LM339 chip issue again (I'll confirm tonight after replacing the LM339s again). So, what the heck is causing the LM339 chips to die? I really don't want to replace the two LM339 chips every time I want to have a game =). Any advice on how to troubleshoot this? I have checked if any connections in to the opto board is shorted etc. but can't find any issue so far.

The issue I see is essentially this, when there's a ball in the right trough, activating a switch on row 5 will also trigger Disaster drop main. I have no issues whenever there is no ball in the trough.

Thanks all!

Well that was my first solution.. there's a brand new opto board in the machine. The LM339 still blows! =)