Check the sound board and driver board for cracked solder joints.

Make sure the edge connectors are clean--they should be shiny, not dull (use a pink rubber eraser to clean them)

He means repin the connectors. You can usually reuse the plastic housings.

If the game is working fine, you may not need to do that, but it can be a source of issues of you are having problems.

I usually head for greatplainselectronics.com, bigdaddy-enterprises.com, mouser.com, digikey.com, and a few other places for connectors, pins, and electronics components. Marco & PBR tend to be more expensive when it comes to components.

I'm guessing what you're looking for might be a quick disconnect terminal like these:

pasted_image (resized).png

There's a brass or phosphor bronze quick disconnect terminal that is a good match to the original terminals--I'll try to grab the part number later tonight.

Using an automotive connector with a bright color on the insulation just looks odd to me in an older game.

Whoops, It seems I got distracted and forgot to follow-up earlier, so here it goes:

quick disconnect terminal .205" 18-22awg Part# 42198-1

http://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/42198-1/A111180CT-ND/4142566

This is what will match the quick disconnect terminals in a system 1 game.

It doesn't sound like a connector issue to me either.

Does all sound appear to drop out, or just certain ones?

Does it gradually fade out, cut out suddenly, start getting garbled before cutting out in some way, or something else?

Can you post a video of what's happening as the sound cuts out?

Pull the MPU and check for cracked solder joints on the back.

I would also take a look at the ROM chip legs for tarnish/corrosion and the socket to make sure it makes contact with all the legs.

Yes, the main board in the backbox. Some people use the terms interchangeably. However, "CPU" usually refers to the actual processor chip on the board.

That power supply should really be refurbished or replaced. Those diodes that are sticking off the board make me nervous.

As for the MPU, it looks like the two chips (Z8 and Z28) in the lower left were hit with alkaline, but not replaced. The first thing I would do is replace anything with corrosion on it. Z8 interacts with the CPU a little bit, so I might suspect there could be something going wrong there.

http://www.pinrepair.com/sys1/#tools

But, if you'd rather just replace the board and not deal with it, that's fine too. Just let someone else have the old MPU if you don't want to keep it--they can sometimes be repaired, the ROM chip can reused to fix other games, or sometimes those spider chips can be used to fix other boards. I pick up boards like this all the time.

$2.60 per fuse? Good grief, where are you getting your fuses?

http://www.ipdb.org/showpic.pl?id=532&picno=43310&zoom=1

There are no 1 amp fuses on the transformer panel.

The primary fuse is a 5 amp slow-blow fuse. Using a 1 amp fuse there instead will blow every time.

pasted_image (resized).png

Oh, I almost forgot--do you have the additional fuse mods installed? One of those is 1 amp.

https://pinside.com/pinball/forum/topic/gottlieb-system-1-small-transformer-issues#post-2392905

I see on clay's site, it's labeled as "primary fuse".

http://www.pinrepair.com/sys1/#addfuses

Ok, so that fuse protects the transformer from input voltage, but it's likely that something is going wrong on the power supply, causing it to draw too much and/or short the voltages.

Can you post some photos of your power supply?

[edit]: Nevermind, I see that you posted some photos on page 1. Yeah, that power supply is a mess. Either refurbish it with new parts, or replace it with an after-market board.

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_1#Recommended_Power_Supply_Updates_.26_Repairs

[edit2]: Nevermind again, lol. I see that you said you replaced the power supply and MPU. What exactly did you use to replace the power supply? There are multiple people creating these power supplies. GPE's power supply has been out of stock for a long time, so it may actually be someone else's that just looks like GPE's design.

Another thing I thought of--is the A2-J1 power connector plugged in the correct way? It's easily reversible, and it can cause problems/damage if it's plugged in the wrong way.

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_1#The_Upside_Down_A2J1_Power_Supply_Connection

On the power supply, disconnect J2 and J3, and try powering up the game then and see if the power supply still blows.

The fuses under the playfield are for the solenoids. You can ignore them for the moment.

Disconnect the power supply completely and see what happens.

If the fuse still blows, there's definately a problem with the transformer panel.

If it doesn't blow, the issue may be with the wires or voltages feeding into the power supply, or something wrong with the power supply itself--possibly one of the rectifier diodes.

Ok, check the voltages on the J1 connector.

Check all the diodes on the power supply with your multimeter.

If you recently bought it, maybe contact the supplier, and explain that the primary fuse on the transformer when just the power supply is connected. It'd possible a component failed or was installed incorrectly during assembly.

Are you sure they were tested properly? Sometimes it's a little confusing.

http://pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier

I've heard of a few cases where a diode would test ok with a multimeter, but fail while under load, so there's that too.