I brought a HGT back from the dead and I'm having a very frustrating issue.

Symptoms: When a coil fires the controlled lamps and GI will dim slightly. At random times a coil firing will reboot the game. Sometimes you can get 4 or 5 games in, sometimes it'll happen in the first few flips. I know at least the flippers and pops can cause the issue.

Troubleshooting already done: I've replaced the rectifier board and tried subbing in Alltek Solenoid board and MPU with no change. The problem persists with the controlled lamps and sound card unplugged. I've tried rebuilding every female connector that can't be ruled out (game still reboots even if the connector is unplugged). The power cord has been replaced. I've replaced the diodes on the flippers with no change and I don't really know where to go from here other than just starting to replace every diode on each coil but there are no other diode symptoms (no multiple / incorrect coils firing). Is there another power related area that might be suspect? Reflow the transformer? Wonky power switch? I've tried wiggling every connector that I thought suspect in case the vibration of the coils was causing it instead of power.

Edit: problem was an out of place, loose diode from a P.O. modification in the slam tilt circuit.

Mpu tp1 is 5.18. Both those connectors have been rebuilt.

I just discovered it still happens if the playfield fuse is out (only flippers getting power).

If 5v was dropping I wouldn't be sure why with all the rebuilt connectors and substitute boards having the same problems. Is there a way to tell if it's dropping without asm oscilloscope or something? If it was doing what would be the cause?

Edit: just tried flipping with my multimeter clipped to the tp1 on the mpu and it stayed solid through the flipping and reboot

Both flippers and the pops will cause it randomly.

It seems like it might be harder to make it reset with the playfield lifted but I'm not sure.

The problem happens with the flippers disconnected via the solenoid board when manually activating pops, and with the pops disconnected via the solenoid board by activating the flippers.

I've got 4 games running on the same outlet that haven't had any issues (only HGT is on / drawing power now so it's not overloaded). How can I test the voltage drop theory if it's something like the power cord, switch or varistor having weird issues? I did check the outlet and it is 119.8. The other outlet on the wall plate doesnt drop below 119.6 during flipping and stuff.

Just verified voltage is staying steady on the downstream side of the power switch

I put the alltek solenoid board back in it and reread all my test points again. Tp3 on the rectifier, tp4 on the solenoid board, and tp3 on the mpu (12v test points) are reading 15.8. I seem to remember there being a higher reading on this line after doing upgrades but cant recall. Is this possibly related to the resets?

After looking at the alltek and my multimeter the 5v does not seem to be wavering at all during the reboot process, at least to the naked eye.

Yes, it's a brand new rectifier. I replaced it after the last one was having the same issues. What I haven't done yet is reflowed the solder coming off of the transformer. I'll give it a shot since it's the other side of the wire and hopefully I won't electrocute myself.

Also not it :/ what else?

I've done a lot of shaking, tapping on chips and wiggling connectors. I can't get it to do anything funky unless could are firing. I'll try again now though and see if I can get anything going.

Edit: holy crap! Even though I've nearly picked this thing up and dropped it in the past, I got it to reset by banging on both sides of the cabinet in attract mode! Good to get it narrowed down! What's next on the list? Power switch? That thing the varistor is on?

Thanks snyper2099 for the breakthrough

It has the same issue with a brand new alltek board. The female connectors have been repinned.

Yeah they're working and make the "sad noise" when activated.

I got a kit so if it is it'd be my dodgy workmanship lol. I'll check it out.

Did a little more playing around and discovered I could make the resets happen by slapping a very particular area of the cabinet. The left metal rail just past the flipper button. I didn't even have to rap on it that hard once I found that spot. So what's behind it? The left flipper button which is held in place with a metal piece and two metal screws. Could one of these screws be penetrating far enough to touch the metal side rail which is in the grounding chain? If it was, could it possibly be the culprit? I unscrewed and re seated the flipper button and wiggled the side rails grounding connection which looked crusty. A bunch of slapping later and no resets yet. I'm cautiously optimistic but I've felt this way about 19 times already during this process and been let down. One thing giving me pause is I tried grounding the different parts of the flipper button and all that happened was the flipper fired (during gameplay) with no reset when I hit the leaf, but that was after I reseated it. Even if the screw did ground out, why would it cause a reset? This has got to be another red herring the more I think about it.

Gotta stop troubleshooting to go to league night, more later!

You could buy me for a freaking dollar right now.

So I got through 5 games last night and on the 6th... reboot. Dammit. After reading the slam tilt comment this morning I was thinking "well it reboots during attract so that shouldn't be it. Plus one of the leafs (leaves?) Isn't there so it's not the switch being too close". I manually tried activating the slam tilt with test leads and... nothing. Gave the diode a tug and it was either running free or very loosely connected on the other side to the yellow wires. This is not his home but he was hanging out there because his entire leaf is missing from the switch! So this little guy is out there under the yellow wires looking like he belongs there and when properly attached he defeats both slam tilts from functioning. Possibly a p.o. fix. If he's loose and I touch him to where he was sitting and bridge the two leafs / wires... reboot. He's now out of play. No diode in place as there is no leaf to ever be contacted and both slam tilts work as designed when bridged. I'll report back after a few days of test play to make sure this is it. Thanks all!

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Thanks, all, for the help!