The boards you have, are they the CPU AND Driver board or just the CPU?

The switch matrix enters the board set through the driver board. If you just borrowed your friends CPU board, you are only testing 1/2 the potential problems. Also, if you are using the original driver board, you are using 1/2 of one of the weakest parts of the system, the 40 pin inter-board connector.

You should replace the 40 pin inter-board connector on these boards before going any further. They are typically flakey after all these years and can cause all sorts of intermittent issues, just like what you are seeing.

Also have a look through this thread for ideas how to make your game reliable and run great for years: https://pinside.com/pinball/forum/topic/vids-guide-to-bulletproofing-williams-system-6

First off I'd like to say that I am no guru myself when it comes to electronics. Swapping out the connectors is really not that difficult to do. Just take your time and read up on it and ask questions in this community. There are a lot of people that will guide you through things. I've never worked with circuit boards myself and was in the same boat as you are. I was very nervous about the fact of removing components and adding new ones. But I said to myself, "what the heck, if I mess it up, I can get new boards anyway". So I went and ordered the parts I needed and went to work. Parts are cheap too. I've replaced all of the male headers and all of the female connectors for all of the circuit boards including that 40 pin connector. It really wasn't as bad as I thought. It WAS a little tedious for me as I don't have steady hands but I took my time and went slowly until I finished everything. A couple hours here and a couple hours there each day after work and I got it finished. I must say that one of the things that helped me the most were this cheesy magnifier head strap for $4.99 from Harbor Freight Tools: https://www.harborfreight.com/magnifier-head-strap-with-lights-38896.html I may have looked foolish wearing them, but they really helped me see what I was doing. In a nutshell, I'm just trying to offer you some encouragement. Don't sell yourself short. You can do this if you put your mind to it. I have the same machine and I am working through a few different problems myself. I have parts coming tomorrow to rebuild the high voltage section of the power supply. You may not have to replace ALL of the male headers and connectors like I did but that 40 pin inter-board is a must that really needs to go. Good luck with what you decide to do. Hope this helps you decide. If you have any questions at all, ask away. I can try to help and I'm sure there are others that are more experienced than I am will chime in to help out.

Before you put any more boards in the machine you have to figure out if you have a short. If you put any other boards in right now you run the risk of blowing another one.

You said column 6, which includes the trough and shooter lane switches. So if you are moving balls around and it acts like it wants to start, then it may be a switch problem or something local, not a blown board/chip.

Here is what I would do:

- Switch test - if you haven't done this yet, it may show you that there are switches stuck closed. You are looking for 17, 18, 19, 44, 45, 46. If any of these indicate they are closed, then adjust the switches.

- Visually inspect all the switches to make sure they are open (not touching) and test all the diodes on those switches with a multimeter

- Trace the wiring for column 6 very carefully. You are looking for anything unsecured, switches that are touching metal or other wires etc. I had a case where a staple holding the GI braiding had come loose and the braiding hung down and contacted a switch. The higher voltage blew the board. Don't forget the rollover switch and the tilt bob wiring that are also on this column.

If you don't find anything, then repeat the process again.

If you still can't find anything, I would call a professional or a friend that knows what they are doing.

Have your buddy put the test board in another machine and see if it works. If it doesn't, then you have indeed blown something and need to identify it.

You can send the boards out to any number of guys here on pinside that will test and identify the problems, repair them, and swap out the 40-pin connector. I recommend this over buying a rottendog, but I have used them in the past without problems too.

This is your first machine, and you don't want to be too frustrated with it by trying to fix the most complex parts of it on your own. Get some help and learn through observation. Have pros do any board work or you could be tracking down issues for weeks.

You can start working on your second machine. That way you have one to play with while you are working on it.

If there is a number showing it means the switch is closed. Look at where the balls are. Are they in the trough? Is there one in the shooter lane?

Those switches should be closed.

Best thing to do is remove the balls. The switches should be open.

Put them back in the trough and 17 18 19 should show up in the test.

Then move one to the shooter lane and 18 17 45 should display.

If these are not your results then look at and adjust your switches.

if you don't know how to do this just google it.

Repeat the instructions I gave before if it's not working. Then report back.

Do not worry about your 40 pin yet. This could be a very simple fix and doesn't sound like a connector problem. You can deal with it later if there are other symptoms.

Do you have a manual? If not download it from ipdb.

Get the Manual here: http://www.ipdb.org/machine.cgi?id=310

Pinwiki help - http://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7

In case you're still looking for a good tech to fix your boards, Chris Hibler has a great reputation here on pinside. Here's the link: http://chrishiblerpinball.com/contact/

45 is the shooter lane not the trough. No ball in the lane 45 will not display.

The trough is where the three balls sit under the apron.

Sounds like you still need to manually test and adjust the trough the switches. Take the balls out and play around with the switches with your fingers. See if you can get them to trigger in the test. Play with it above the trough and below.

Also check the other rollover and tilt bob on that column and see if they trigger in test mode. Just to make sure the column wiring is working.

The game won't start unless all three balls are seen in the lower or upper trough.