I've been trying to track down a CPU reset problem on my Jurassic Park since I bought it 4 years ago. The CPU would reset if the volume was turned up very high even without any coils firing. This isn't usually a problem because it has to be high enough that it's uncomfortable. But sometimes if I have it turned up and get multi-ball I get resets.

I went through everything and finally noticed a broken off header pin at CN21 Pin19 for the Sound ribbon cable on the CPU. I don't know if that's the cause but it isn't correct (I can see a test point on a trace connected to that missing pin marked "E"). I enclosed a pic of the Header pin and the schematic if anyone has the time maybe you can tell me if it might be the cause. At any rate I want to replace it.

My question is, does anyone know where I can buy the header pin replacement? Thanks!

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CN21 Pin19

IMAG1575.jpg

BTW, I can't get the CPU to reset/reboot with the sound board disconnected. The sound board has reflowed solder and new caps and seems to function as it should.

Thanks guys. Damn, I thought I was on to something. I found some pics of the board online that showed the pin in place.

I have a Pinscore power supply that I installed when I bought the machine. The next thing I was going to do is replace the connectors from the PS to CPU. Probably should have done that already but they look perfectly fine. Then maybe follow the power going to the PS. I think there are some voltage regulators but I'm not sure.

I don't have a working DMM at the moment. I've been using an el cheapo Radio Shack, but it started freaking out the other night. I was going to replace the battery but I think a better fix would be to replace the whole thing with a better model.

Thanks everyone,

Okay so I replaced the molex wafer connectors on the power supply that supplies power to both the CPU and the Sound, then I replaced the corresponding molex connectors on both boards. I didn't see any change. I decided to leave the missing pin alone since the consensus is that it doesn't seem to have a function.

I got a new DMM so I checked the +5 voltage on the CPU and got 5.03 - the test point at the reset was 4.6. The power supply test points checked out perfect. Any Ideas?

I'll pick up some alligator clips for my DMM tomorrow and see if I can see a drop in voltage when I get a reset.

I still have the original PS. This was my first machine so I just replaced the PS (and the PPB with a rotendog) when it didn't power up correctly. I got the original out and it looks really nice. Only repairs that I see were fuse holders. I'll plug it in and check it out, maybe I can fix it and try that.

Does anyone offer a rebuild kit?

Okay, so the reset problem is fixed! It was the Power Supply. I plugged in the old PS and checked the +5 and found it to be 2.9 so I first suspected the cap at C2, I replaced it and now have 5v. I also Had + - 12v so I plugged everything in and it played without any resets. I really didn't suspect the Pinscore but it seems to be the culprit.

But now a few coils aren't firing! I'm finding out which ones at the moment

The coils all fire in test and the switches are good but when I power up now (but not when I did the first time) it thinks a ball is missing. But it looks like the coil in the trough is sticking on. It isn't getting hot but it's on and not allowing the ball to go into the shooter lane.

I'm not sure where to check the voltages on the PS other than the 5 and 12. Can anyone give me an idea what to check next?

Thanks

All good. I think I must have bent the switch for the kicker in the trough. I dropped a screw when messing with the power supply and I lifted the playfield awkwardly to look for it. So It's all good. for now. I'm going to replace the fuse holders on the PS yet. One of them broke off and I have the fuse soldered on one end for now.

Thanks guys. I'm glad viperrwk mentioned that post, I just wasn't suspecting that board at all. Not sure what's wrong with it but it was like that from the day I installed it. Fortunately this machine is bullet-proofed everywhere else!