Hi all,

So I was a naughty boy and was fiddling with a non-working pop bumber on my TAF with the machine on and blew out F115. Disconnecting J114 the fuse stays ok so that led me to the MPU. I checked the 4 LM339 using a multimeter (red on ground, black on each leg) and each one was short on the vcc leg. That isn't good right?
I also checked the ULN2803a and this was also short on the vcc and also had a diode voltage drop reading of only 0.06 on leg 16 (I think). The fuse remains ok with the 2803 removed.

Is it possible that I took out all the chips even though the fuse holds with just the 2803 removed? Does all that make logical sense?

Would be grateful for any pointers. Really annoyed as it was working nicely!!!

Many thanks,
Ig

P.S. Also, when I buy a replacement for the ULN, I can't see that there is any difference between a 2803a and a 2803. Could someone kindly confirm if they are exactly interchangeable? Many thanks.

Thanks Pete! Yep, I foolishly didn't recheck the LM339 chips after pulling the 2803. Looks like the are actually fine which is good news given they are soldered whereas the 2803 was socketed. Thanks also for the confirm on the 2803 spec. Hopefully a new one in the socket will get me back and running. Just as a precaution, is there anything I should check before turning back on that might still cause the 2803 to short again. I would rather not burn through my limited 3/4 amp fuses! I am not really sure what specific action of me fiddling with the bumper switch leaves was the offending one!

Many thanks!

Thanks guys. So the good news is a new 2803 has worked and now the games boots etc. Super. But then the agony. I am guessing that the jolt to the board took out more than the 2803. The switch for the thing/skillshot hole has gone and the bookcase won't stop turning so game remains unplayable. So two questions if I may: 1/ does it makes sense these are a direct result of what also caused the 2803 to go? 2/ what switch/sensor is causing the bookcase to not stop moving? Test report mentioned Thing Opto and Opto limits but not the thing hole switch. I also know I have a switch out on a ramp and in the swamp lock and oddly those are not reporting as at fault.

Grateful as always...

Ig

Ok, slochar, I will check the opto board but I imagine it will be ok as the bookcase opto switches are registering ok on the switch edges test. Will revert.

Ok. So opto board looks fine. Led1 comes on and, as i say, bookcase greed optos working. Ran the Thing Test and Bookcase Test and this might be the issue (see photos). Surely one and only one box should be checked in each of those? I am guessing it is no coincidence that the Bookcase Open/Close and Thing Optos are on column 8 of the matrix...... What's my next step!?

Grateful as always....

20221023_173601 (resized).jpg

20221023_173615 (resized).jpg

Oh man! I should know better than to try and do anything on a Sunday evening! Have now screwed it up further. Was testing the opto board, saw smoke coming from somewhere (can be sure where) and so turned it off. Now the Led1 on the opto board is out and the bookcase greed optos have gone!

Ok, 12vu repaired (had blown the F116!) Phew.

Here's a picture of the T1 display. Clearly shows the column 5 bookcase switches out (if I am reading it right). So now do I follow the circuit from that column and hope to find a blown transistor or similar or does something else I'm not thinking about cause this...? I haven't shorted the row/column pins yet to see if they trigger but will do that later if appropriate.

Grateful as always...

20221024_172915 (resized).jpg

Yep, that all makes sense and agrees with what I posted in post #9. This is indeed odd. The Upper right jet is the one that a fiddled with that set this whole set of screw ups in motion! (Shoved a rag in the ball shoot being lazy!)

OK, I already know the Grave A and the Thing Eject do NOT register - Is that a clue? Was surprised at the "A" when testing everything yesterday. How is that connected to the root issue?

I will try jump tests tomorrow evening. Thanks. Bringing it all back to the original cause that I blew out the 2803 on the MPU fiddling with the bumper, I would be surprised if it was a wire break issue. I hold hope with the +12vu being dodgy still. Will revert once I have tested.

Thanks as always. I really am very grateful for the time you guys spend helping us.

Totally agree and am doing this step by step following the great advice. Learning and understanding along the way which is even better! Will revert once I have had a chance to do the jump tests.

Many thanks.

Okey doke. So I ran the jump test ( I assume the J206 and J208 shouldn't have connectors on them (because mine don't!) and are just run throughs for J207 and J209. That's what the schematic looks like)

What I get is hopefully a good clue to what is going on. I short the J206-9 to each pin on the J208. 1 and 9 do nothing. The others each "open" the boxes in column 5 on the switch test matrix. BUT also a couple cause other "boxes" to close. In particular, pin 2 causes the Jet bumper at 33 and 35 to fire. Does that mean I have someting going wrong in the wiring near the bumpers?

Sure, I appreciate that. What I meant was that the connectors pins have no connector "plugs" associated with them on this particular board.

OMG guys, I may have been wasting your time since post #6. I just took the approach to re-check what I did to fix the original probelm before the new issues then started. So I checked the seating of the new 2803 and found I had bent a leg on insertion. So stupid!!!! Sorted that out and now the bookcase and thing eject hole are working again. Still got an issue on the Thing Opto and a couple of other switches but that is for another day.

Thanks and apologies in equal measure!

Very much so Pete!

Infuriatingly, although everything is back to how it should be and playing/registering properly, the thing eject hole solenoid is now failing to push the ball out of the hole. It fires but the ball doesn't get over the lip. Never used to be a problem at all. Was there perhaps a little "seat" the ball sat in to give it a little height over the edge that may have dislodged? I can't see anything that has fallen under the playfield. Would be a very strange coincidence if suddenly the solenoid wan't nw receiving enough power. All the others seem to be punching their weight when I run the solenoid tests.... Grrr.

Checked the voltages - fine. Took the solenoid off the playfield - looked fine. Fired it while off the playfield - looked like it was fully extended so fine. Put it back -same behaviour. Then I thought, hmm, I've moved the table a bit to get to the back so maybe it's off level - put a beermat under the back leg and that was enough to help the ball on its merry way! Oh the joys! Now playable again. Yay. I will level the whole machine properly when I have finished the last few switch repairs I need to do!