1. Bulbs. The connectors aren't rated to handle the amount of current that the bulbs draw, so it's inevitable that they burn up. One way to solve the problem is to switch to bulbs that draw less power, like 47s instead of 44s in GI, or LEDs. You can also help it a lot by simply setting the GI power saver to 2 minutes, level 4, which will dim the GI whenever the game is sitting turned on but not being played.

2. Just look at the header. If the pins look bright and shiny, they're fine. If they look white/oxidized/black/etc you should replace them. Some people replace them always, just to be sure. It might be overkill.

3. It can happen fast on location. I put out a bunch of games last year, some of which had rebuilt connectors, and some of their new connectors (with the superior trifurcon pins) have started to cook already. In home use I would imagine it would never happen unless the game is turned on for 8+ hours a day.

4. Yeah, leaving it unplugged is fine.

As for how the guy who shopped the machine missed this.. Someone who knows what they're doing probably wouldn't miss it, but it happens all the time. That connector is actually nowhere near as burned as many of them can get, so I could see how if it had remained plugged in a seller could overlook it. It's likely out of ignorance, not an intentional attempt to mislead you. Probably half of the games I've bought, including many that had been shopped by collectors, have had burned connectors. It's just not something some people are tuned into. Generally a "shop job" consists of work done to the playfield, and of course everyone has different ideas of what that should include. The term is loose at best. Whenever I buy a "shopped" game I fully expect to have to re-do half of the job myself, not to mention fix all kinds of other issues that the seller probably never even realized the machine had!

I had the exact same thing (same pin even - 2nd from left on the J121), had it repaired (pins replaced, etc.) and now it heating the connector again. I didn't think I would ever LED a pin but I am in the middle of doing my STTNG right now to lower the power draw. I am thinking that will take care of it but that's more hopeful/minimally educated thinking than it is actual knowledge/experience.

Very common on Williams GI of that era, you should have seen how bad mine was, connector was cooked right off and whoever had it before me just soldered the bare wires directly to the pins! And where the pins had cooked away they soldered wires directly to traces on the board itself!

they also cook because the original molex and pin is a piece of shit. The new tri type pins, make better connection for current. So they don't heat up as much. LED's will also help. For backboxes. I usually pull all the bulbs out except for 7 of them spread out evenly over the entire backbox. It will light the entire translite, and reduce glare off the glass by about 73%. Never cook your Backbox GI molex again and looks just as good as the full box full of bulbs does.

47's are less heat, less light, but not noticeable reduction in light, but will help the strain on your connectors.

You'll need a crimper if you don't have one, and of course the header if you want/need to replace it. I didn't look up the numbers you posted, make sure you get the trifurcon connectors. If you haven't done this before, get plenty of spare connectors, the crimp can be a little tricky at first.

I don't think Ed will do pick up service, but shoot him an email, he's very helpful.

You can get everything you need from him.

This happened on my T2. I think it's time for some LED's...

Here is the crimpers (the one at top of page)
http://www.greatplainselectronics.com/Category-138.asp, Made in USA
Also known as "BCT-1"
They are at Great Plains

Mine too, but a different connector.

Went ALL LED, and then replaced connector. We will see how it goes. Tomorrow is power up day I hope.

As others have mentioned this is VERY common on WPC and WPC95 games. In my experience this is the most common non mechanical problem. (Followed by bridge rectifiers on WPC)

IF, you can perform minor board work, I'd replace the header pins too. Get the high temp ones (I believe they are black rather than white)

With the trifurcon connectors you will probably be fine for home use. Remember these things were typically setup somewhere and were turned on for hours on end.

In it's simplest form> Connector resistance + voltage load = heat/burned connection <

This is the reason why I am LED'ing my JD right now. Less heat and less power are a BIG deal in keeping the lifespan on these pins long. Plus, if you like the way bulbs look there are so many options now to get the benefits of LED's and keep it looking retro.

The short answer is Molex connectors are inexpensive, crummy connectors.
They fail because the tin plating oxidizes and creates a high resistance
connection which generates heat, which encourages more oxidation.
The fact that there is a small point of electrical contact doesn't help.
Another failure mode I've seen is where the female spring contact
cracks at the end where it is folded over.

Molex did make pins for their connectors which are gold plated, and
I have used these succesfully but they are hard to find and expensive.
Steve

A plastic piece that fits into the connector instead of a contact. It won't allow you to plug the connector in wrong, the keying plug blocks the header pin.

one of the holes in the molex has a plastic plug in one of the holes. On the board, one of the pins is cut off, so the only way to get that plug on is to have it lined up right and facing the right way.

That's the little white plug that you can put into one of the connector positions to "key" it or "index" it so it can only plug into it's mate the correct way. It prevents you from plugging the connector in backwards.

A keying plug is for where there is no pin so that you can put the connector on correctly and not accidently reverse it when you put it on.

Plus the fact the circuit passes through multiple connectors and the connectors are being operated at the very upper limit of their specifications. In other words, poor design.

The reason is the connectors are SHIT and very poor design. Early Bally ss and Sterns did it ALL the time as well. You THINK someone would have learned from that . GI connectors on ss Bally and Williams games been a problem forever...

And Data East... Same design as Williams 7+

At the time, there wasn't an incentive for pin makers to design/use components that would last more than 5 years in operation. Probably a bit of planned obsolescence going on.