DE Jurassic Park tech questions

seanriddle

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I picked up a JP in pretty good shape, other than being very dirty. I've been working on getting the electronics working- resoldering a few broken wires, replacing a bad diode and a bad transistor, etc. I noticed the coil for the diverter wasn't installed and the associated flashers weren't working.

I assumed Q41 on the CPU board was bad, but I installed the coil first. When I turned on the game, the diverter coil stayed on during diagnostics, so I checked D14 on the PPB board and it was shorted. I didn't have a spare on hand but I clipped the diode. Next time I turned on the power, there was a loud buzz; so I shut it off quickly.

After a few more short power ups, I noticed that several coils were immediately coming on and staying on- all of the coils numbered 1-8: diverter, knocker, ball release, auto launch, etc. I pulled connector CN11 from the CPU board so I could power up for testing without burning the coils up.

These coils aren't driven by a PIA; there is a latch on the data bus that goes to 2 AND gates for blanking, then to 2N4401 driver transistors then to TIP122 transistors.

I used a logic probe to look at the AND gates, and they are being driven correctly, but the outputs are bad. I clipped the one at 3J and the signals didn't change, so I'm guessing that means I blew my 2N4401 driver transistors, and likely the TIP122s.

I can replace all that, but I'm trying to figure out what I did wrong. Was this caused by powering on the machine with D14 on the PPB board clipped? I don't see how that could be the case, but that's the last thing I did before this happened.

Afterwards I measured voltage on the PPB board, and J6-6 is about 43V. I hadn't measured this before, so I don't know what it was before all this happened, but the PPB schematics say +28V; however, the coil wiring diagrams on pages 31 and 38 say 32V and the P/S schematic on page 57 says 34V. This comes from BR2 on page 47, which is fed with 25VAC, so 34VDC seems correct.

Maybe there's a short between 34V and 50V on the PPB board and the 15G470KM on the P/S board is holding the 34V line to 43V?

Thanks for any ideas.

Sean
 
I found part of the issue causing my 34V line to be 43V - the transformer was jumpered for low line voltage. I switched it back to normal and it dropped to 40V. Still seems high. If I unplug the transformer from the rest of the game I measure 30.5VAC on the wires going to BR2. Before I changed the jumper, it was 33VAC. The manual shows 25VAC. I'm not sure if this is normal or if it indicates a problem with the transformer.

I got a box of parts from Mouser and replaced D14, Q41, Q33, 3J and 4J. Now the coils work again, along with the diverter. But the flashers associated with the diverter, 6R, still don't work. I guess I need to trace the wire and see if it's broken somewhere.
 
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