Turned on the sharp shooter today and it’s acting up. Top left pop bumper actuates randomly. When the ball goes in the drain it won’t spit the ball back out. The coin counter keeps going up randomly. Some of the play field switches aren’t working. The relay on the spu clicks randomly. In test it has the slam switch closed. So I tested all the switches thy are fine. Unplugged the slam switch from the mpu and it still shows it’s closed. I’m guessing this is on the board (or boards) but not really sure where to start. Hope someone with more knowledge then me about game plans can point me in the right direction.

No one else has had issues like this? Just want to hear what you guys think.

Thanks for the reply. When I got this pin about 5yrs ago the mpu would not boot. I re-caped the whole board, replaced some ics on the clock circuit, all the zener diodes(I had them on hand), completely rebuilt the sister board, and replaced the z80 cpu. I’ve read the same as you and even though it got replaced 5yrs ago I replaced it yesterday with no changes. I was hoping it would be something easy in the switch matrix but my trouble shooting leads me to believe otherwise. The issues are on multiple lines and the slam switch stays closed even after unplugging from the mpu. Not sure what to make of this but when in test slam shows closed which is 003 no other switch will register except for 001(account reset) and 002 (game start). I’m just hoping it’s not the roms as that might price me out of fixing this if I have to buy a burner.

I did not replace the filter cap. Looks as though someone has in the past. Checking for ac ripple on the filter cap returns no ac voltage reading on the dmm. I know it’s suppose to be under .200v but is no reading acceptable or should I be seeing some voltage. All voltages on the ps check ok except 12v measures 14.5. I know It’s suppose to be within 12v to 14v so I’m guessing that’s ok unless someone tells me otherwise.

Yes, test mode shows 030 pulled j6 and still shows 030. I did swap out U14 with one I had on hand but who knows if it’s a good one it came out of a bin I acquired years ago full of ics. So this is gonna be your third then

Figured that since 010 and 020 will display when closed but thanks for the info.

Sorry I wasn’t clear on that. No it did not fix it. The problems seem more random every time I turn it on as in sometimes the flippers work sometimes they don't. Sometimes the start button starts the game and other times pressing it scores points. All this happens with the old U14 chip and with the one I replaced it with.

Yes still shows 030.

I can borrow one from my dad and post the results. Seeing as I haven’t used a logic probe since I was a teenager and my dad was always over my shoulder telling me what to do raises a couple questions. Is this cmos? ttl? And where am I grabbing power for the probe? Thanks for all the help. It’s greatly appreciated!!

U23 pin 14 = 0.0
U18 pin 14 = 0.0
U18 pin 2 = 3.1
U18 pin 13 = 0.1
U18 pin 1 = 1.8
U23 pin 13 = 0.0
U23 pin 1 = 0.0
U23 pin 2 = 0.0

Double checked the measurements this morning and voltage on u18 pins 1 and 2 are bouncing up and down. All the rest are still it zero.

U18 pin 1 Reads 1.8 but bounces.
U18 pin 2 reads 3.46 holds steady this time. All the other pins read 0

All pins measure 4.86

I don’t have one on hand so I’ll have to source one. In the meantime if you want me trace down the resistors I’m willing if you are. I do have the schematics and basic (very basic) knowledge of circuitry.

Here you go.

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Cleaned the resistor area, desolderd then resoolderd the three resistors and it seems to have fixed the problems. I will remove U18 clean it all up and install a new chip since I ordered them already. You the man Quench !!! Thanks for all the help it is greatly appreciated.

I spoke too soon. Played it for a little bit and some of the symptoms returned. Getting 1.5v on U18 pin 2 and 0.05 on pin 1 now.

Seeing as it’s the weekend I’ll probably just wait till the new ones arrive on Monday and replace the old one. At least I got to play a few rounds

Removing U18 revealed more corrosion. Cleaned everything up and then the mail came and no chips so I put the old one back in fired it up and played it for about an hour . Thanks again for all the help!!! If I was 20yrs younger I would have spotted that corrosion in a heartbeat. I swear the day I turned 40 I couldn’t read small print anymore. If your ever in the Tampa Bay Area let me know, I owe you a beer or two.