Ground Short row 1

[pinball god]

Hi all. Thought I'd do a flipper rebuild on my TZ and all went without a hitch. Power on and I get GI's and the boing noise but the DMD is stuck on testing. Did this a few times and looked to see if I bent any wires etc that may be be shorting. I repositioned a few resistors and powered on and still get the same with the added sequence like a ball search happening and then the DMD displays "GROUND SHORT ROW 1 IS STUCK CLOSED".

Ok so WTF???

Any ideas? And also could this be caused by me doing the rebuild or is it coincidence? Thanks

[pinball god]

I took off the flipper coil I did the rebuild and accidently touch a switch and saw i spark. The game was off at the time but now I have the additional error check fuses F114 & F115. They seems fine. i replaced F115 but don't have a 8A 32V for F114. Closest I've got is 8A 240V. But like I said they buzz fine

[dj10555]

The driver board caps hold their charge for a short while so touching the coil to the switch has probably blown the ULN2803 chip, which controls the switch matrix on the CPU board. Another indication of the chip being faulty is the fuse error F114 and F115 when the fuses actually measure alright. Unfortunately the chip is soldered in on the TZ CPU board.

regards Derek

[pinball god]

The driver board caps hold their charge for a short while so touching the coil to the switch has probably blown the ULN2803 chip, which controls the switch matrix on the CPU board. Another indication of the chip being faulty is the fuse error F114 and F115 when the fuses actually measure alright. Unfortunately the chip is soldered in on the TZ CPU board.

regards Derek

Thanks Derek. So what does that mean for my TZ? Am I screwed or is it repairable? I have checked everything and it all works but all my switches are dead. Coils & solenoids good just the switches

[Homepin]

I would say 99% for sure you have cooked the ULN2803 chip - IC's don't take kindly to being shorted or having voltages applied to them incorrectly and will evaporate in milliseconds! It is mounted about the centre towards the bottom of the CPU board. Fit a socket so it is easy to replace next time. If you don't feel comfortable about removing the IC and fitting a new one there are plenty of talented people on this board who can help you.

[robm]

This exact same chip was my first replacement job of soldering/desoldering on a PCB - i was a bit nervous, but in the end its pretty easy.

Snip the legs off the top side of the existing IC, then with your soldering iron heat up the "legs" that are left in the holes and use a little $12 solder sucker thingo from jaycar to clean the holes out and remove the legs.

Give that area of the board a quick clean

Solder a socket in (this is where you take a deep breath, relax and maybe use a magnifying glass)

Push the new IC into the socket


Done!!

[pinball god]

Thanks guys have ordered a couple of chips and will get some sockets from jaycar. I've got soldering braid and a sucker that I hope will do the trick in removing the IC.

To keep everyone in the picture, I removed the matrix plugs from the CPU board to confirm whether the chip is most likely gone and the did error remain. What I don't understand is the sequence of events that led to my problem. After the rebuild, I switched on and the boot seemed to just freeze after the boing and no insert lamps. I then played with a couple of switches cuz I had a feeling I may have a short. Switched her back on and I get like a ball search thing happening and the SHORT error (still no fuse error). All lamps now working. When I removed the coil and zapped the switch, then I got the FUSE error.

So my question is, do you think U20 was gone prior to the zap I noticed? What shits me is I didn't test the machine before the rebuild so don't know if this was present prior.