Hi guys, not to beat this to death - but the Opto on my RCT has a receiver board that sits right next to a metal lug (I don't know the part exactly) when the playfield is lowered. This causes the board to short out, and then you're out another $$ every time.

I am awaiting a replacement, and will make sure there is some type of good solid insulation between them, but in the meantime I would like to bypass this OPTO to make sure the other switches in series are all working.

I see that the transmitter has a 2 wire connection (+/-) and the receiver, logically, has the same power connection, plus 2 additional connections. Is this a simple NO/NC type deal, or is the receiver board sending some digital or analog information back to the CPU to show state? I want to be able to 'plug' this hole so that the other micro swiches in the series will work and I can more fully test the machine. I might also decide to bypass the OPTO all-together if it continues to be problematic.

Thank you for your time and assistance!

Adam

Well I replaced the OPTO and it's working great now. I can run my finger through it and see the red LED light up. But none of my other switches on that circuit are working. It's maddening as they are seriously important switches for the play of the game.

The tech report shows no issues, or any switches stuck closed. I'm at a loss now. The plugs in the vicinity are all numbered by marker, which makes me think someone disconnected them all at one point and checked them for continuity. I would think if something had shorted and blown anything on the main board it would be obvious?

Guess I'll need to find a local repair-person to see if they can fix it

Ok thanks for keeping me honest. I'm NOT giving up so easily

After a VERY friendly call to Stern tech support, he showed me how to pull the two connectors on the CPU board for switch column and rows, and jump those while in switch test to see if the problem was on the playfield / wiring or on the main board. Turns out that Pin6 on the column set of pins did not register a switch when jumped, while all others did. That leads us to believe that the associated 'Q' transistor is bad, and that it's nothing with the hardware below.

So I have some transistors on order for next day delivery (of course Amazon only had them in qty of 100 for next day. I need 1.) But for $8, if it fixes my $400 pinball machine, I'm still ahead!

I haven't ever replaced a transistor before, but my soldering skills are average+ and I think if I'm careful it shouldn't be too big of a deal.

Now if this doesn't fix it, I'll be back to scratching my head again.

Will do. Thanks for the advice! I pulled the board and while all of the transistors looked fine on the front, the backside definitely tells the tale. Sure enough, Q5, the circuit in question looks like somebody took a match to the back of the board between those three pins. I think I might pick up a higher precision soldering iron before I dive into this one.

Thank you guys! Here's hoping this will get me back to 100%!

Oh hey - and while I have you guys here... I ordered updated ROMS for the CPU and Display, and I also ordered the NVRAM RAM replacement so I can pull the alkaline batteries. Do I need a chip puller to get these things out or is it a matter of gently prying / twisting at both sides with a small flathead screwdriver? It's been a LONG time since I pulled any ROM chips from anything.

Thanks!
Adam

Perfect thank you!

Desoldered the transistor no problem. I'm a little worried about the traces on the board, as it's pretty fried on the back. I think they're all intact, but I suppose all I can do is attach the new transistor and hope for the best. Will know before end of the day tomorrow!

At least I know what caused the blown transistor, and have addressed it, so if this fixes my issue it should be good for a long while.

ok I'll try to clean it up. I've never seen or used a fiberglass pen... will try to locate one at a local electronics supply shop.

Success! I received my pack of 100 transistors from Amazon.com (next day delivery, can't beat that) and soldered one onto the board using the existing remaining solder points (I know, it's not the way a perfectionist would do it, but I didn't want to use any new solder and risk jumping the points. There was 'just the right amount' left in each of the holes.

Anyways, after installing the new transistor (and an NVRAM memory replacement) I re-installed the board and connected everything up, and for the FIRST TIME, all of my switch tests were a success.

What a difference it makes when you have the ramp sense switches working (kind of a big deal!) plus a number of other sensors at the rear of the table. It's definitely a whole new machine, and the fun and scores have skyrocketed.

Thanks to all for the support and assistance. There's definitely a sense of satisfaction from fixing this myself vs. paying someone a few hundred bucks to do the same, or shelling out MANY hundred bucks for a new CPU board.

My $400 pinball machine is still a bargain afterall

Well I should add that the damned thing failed again. Opto went out, and transistor went bad after. I pulled the opto and ordered another one. Tested voltage going into opto and it seemed fine. Not sure what's happening. This time, however, I completely desoldered the 'old' transistor and put a new one in after removing all old solder. Nice and clean, with proper length legs and all. Everything but the failed opto is working again (meaning all of the switches that run off of the column Q5 handles) - so we'll see how long it lasts. I just can't imagine what is causing it to fail. But since I've only tried one Opto and one transistor, I'm going to give it another shot with fresh parts.

Adam

Looks like voltage being introduced in the line, killing the transistor and Opto. Don't know why or where though. Crap.