Playfield swap on my DE JP resulted in magic smoke from the CPU board. I'm pretty sure I have the playfield issue fixed but now I'm fixing the board. I replaced a couple bad transistors Q26/Q18 and Q43/Q35 the only components that still do not work are associated with the Q43/Q35 components. Poking around, I noticed the center leg of Q35 had continuity to ground. I pulled that transistor and the trace looks good but still continuity to ground. Could I have shorted out the resistor at RA10? It only shows ground to the pin associated with Q35, all other pins seem fine. I'm likely going to pull that resistor network and check the pin continuity to ground when I get home tonight unless there are any better ideas.

I pulled the resistor at RA10. I was still getting continuity to ground at the center pin location of Q35 as well as the corresponding pin location at RA10. I thought that maybe it was solder at the center pin of Q35 so I lightly cleaned the hole with a tiny drill bit (by hand). Now I no longer get continuity to ground at the Q35 nor the RA10 locations.

How the heck to I get a transistor back in the Q35 location without having my continuity to ground issue now?

So, I got some components in order to be able to replace what I thought would need to be replaced. The ground at center pin of Q35 was bothering me, I decided to pull the resistor array RA10. I still had ground at the center pin of Q35 as well as the corresponding resistor pin location.

I used my spare CPU board (DMD issue but everything else works) as a test case to compare. I started to poll around the traces and came to the conclusion that the source of the bad ground was the component 7408. I swapped this component with the spare and fixed my continuity to ground issue.

See pic below, red trace is what I figured was the source of the ground.

I am still having problems with my solenoids.... see other pic (highlighted coils do not work). Is there possible something further up the line that is causing me problems?
JP_DeadSol (resized).JPGJP_Ground (resized).JPG

The continuity to ground has been fixed but I still have several coils that still don't work. I've been working at one at a time, the coils associated with Q43 (left scoop and some flashers) but I'm starting to wonder if they are party of a bigger problem.

Double post

About this.... How does one do this? I tried and caused more damage but I likely did something wrong.

All coils fire (at least the L side) in this test. Since most coils fire both L & R, I assume there is not an issue with the L/R relay.

No battery corrosion on the MPU board. Coil mounted diodes... I think are fine but the only way of knowing for sure would be to clip them, most of them were replaced during the playfield swap. I was able to fire all coils by grounding their specific transistor, even the particular ones that I cannot fire in diagnostic tests (except for the dino mouth coil but that could be other issues).

Any tips on that?

I would do this if I had any on hand or had a local supplier to get them asap. I do plan on ordering from GPE as soon as their website is back up.. in the meantime, it is test and if needed replace with components from the spare board

I'm thinking the 74LS273 may be next. I checked the pins on the 7408 chips, things seem mostly the same. I checked these while in Diagnostic Mode, flasher test. As the game would cycle the flashers, I would see the voltage on the pins jump. 3.5V on the same pins 7408 to 7408.

Tim, you have a 74LS273 chip?

Coils 4L & 4R (left scoop and some flashers) are the ones I'm trying to resolve, they fire if I ground the transistor but won't fire in diagnostic mode. I have replaced everything on that coils path from the 2 transistors, the resistor array and the 7408.

GPE site is down... supposed to be back up soon. Grrrr

LOL..... Sure, use logic.

Are you suggesting that I look at the components between the TIP102 transistor and the 74LS273 chip?

Looking at the schematics, I may have missed checking the RA26 resistor array as well as R76. The transistor at Q35 had been replaced.

I'm confused now... After looking over the schematic for a bit.

I've been concentrating on the Q43/Q35 components... Says SOL. DRV 4
This is the transistor Q43 that I ground and get the coil to fire.

What is SWITCHED SOL. DRV. 4 on the CN19 plug? Should I look at that?

I'm going to double check 7408 again tonight but I'm thinking it is good. So that means something between the 7408 to Q43 is bad. I did end up replacing everything in that string except those resistors (RA26 and R78).

Fixed. Replaced RA26 after measuring very high resistance from center pin of Q35 to ground. All the other transistors measured about 1k ohm but this one was up in the mega range.