I was recently contacted by a dude in Cambridge with a non-working Bally Paragon. He said that he's had the game for 20 years and it worked great until about 10 years ago when it suddenly stopped working. He brought me the game so I could do a proper repair & shop job. (I won't do house calls anymore because the machines always need way more work than I can reasonably do in short home visits.)

There were lots of problems with this game, but the one issue that nearly drove me over the edge was the following:

The MPU was giving 3 flashes. I managed to get the game to fully boot up once or twice, but the left slingshot coil would lock on and the board would lock-up quickly. I figured the locked on coil was probably unrelated to the problem I was having with the MPU and was more likely a driver board or connector issue.

The MPU would boot up on the bench each and every time without issue.

It had the original battery installed, but the board still looked great. I removed the battery to install a memory cap and found not one spec of corrosion. I replaced the 6820 at U10 because that chip is the typical problem when the board flashes only 3 times. This did not solve the problem, so I replaced the socket as well. That didn't fix the problem either.  

Next, I grabbed a known working MPU, installed Paragon roms and put it in the game. This board also gave 3 flashes. I tried the original Paragon board in another game and it had no trouble booting up. So the issue was clearly not board related.

I scratched my head a few times and figured I'd re-pin the important connectors, just to rule out any connector problems. I repinned J4 on the MPU and J3 on the driver board. The power supply also needed to be rebuilt, so I did that and repinned the power supply connectors.

Still 3 flashes.

I removed all of the connectors from the MPU except for J4 so that I could isolate the problem somewhat and tried again. This time the board would give all 7 flashes. I added one connector at a time until I found the one that would prevent the board from booting up all the way. J2 was the culprit.

MPU J2 is the playfield switch strobe/return connector so whatever is causing the problem seems to be related to the switches on the playfield.

Next, with MPU J2 installed, I removed power supply connector J1. This connector supplies GI, solenoid and switched illumination voltage to the playfield. The game booted without issue. So clearly the problem is related to voltage affecting a switch on the playfield.

I lifted the playfield and searched around. Remembering that the left slingshot had locked-on when I did manage to get the game to boot, I paid particular attention to that area.

I found that a wire going to a GI socket beside the left slingshot had become disconnected and moved into contact with the left slingshot switch. I said "a-ha!" and swore at the wire a couple of times. Once the wire was moved and the game powered up, it booted into attract mode and played no problem.

I chased my tail on this issue for way longer than I should have. Hopefully this knowledge saves someone some time in the future.

Corey

wow, tks for sharing. I like the way you did it.  I will keep that in mind.

Yes... Good post, Thanks.

You are not the only one with a similar issue however.
I bought an as-is Nitro Groundshaker for cheap many moons ago,
because the tech could not figure-out why the game would not boot,
even with a new MPU or Sol.Driver.

See my earlier post here:
http://archive.maaca.org/s107351202.onlinehome.us/cgi-bin/Blah/Blah.pl?m-1233763841/s-4/highlight-Nitro/#num4

Cheers,
- Sylvain.

So what's the lesson here? Look for loose wires near trouble spots before doing anything else? Loose wires are (relatively) easy to find and fix.

We could learn a lot from House MD when diagnosing pins. Look for the easiest to cure problem before anything else.

Painful story, happy ending.

Hate to say it but I would have examined the area around the slingshot right at the get go as it is a lot easier than changing pins, etc.

However I commend you on your willingness to roll up your sleeves and get right into the boards/connectors...in this case unnecessarily!

Quoted from jonny_eh

So what's the lesson here? Look for loose wires near trouble spots before doing anything else? Loose wires are (relatively) easy to find and fix.

We could learn a lot from House MD when diagnosing pins. Look for the easiest to cure problem before anything else.

Well, Jon, I suppose that the lesson here is that the built-in diagnostic tools in old Bally/Stern MPU's don't always point toward a board issue like one might normally suspect. The easiest solution in this case would be to replace the U10 IC and/or socket, which is what I did first.

Having repaired a few dozen of these games over the last several years, I've never encountered a problem with a MPU where the cause was neither board nor connector related. As a result, therefore, that is where I focused the majority of my energy when trying to determine the solution to the problem. .

I figured I would simply share my findings with the class. I apologize if my post got in the way of all your tech tips and helpful solutions. I'll try to remember to look first for the easiest solution to such problems in the future. Thanks for the great advice.

Having done my share of home service calls for solid state games I can state the following without any edits.

First, I interview the owner with key questions, and demand clear answers. Once I have gotten what I believe will reduce doubt & variables, that is when I decide if it is home service or shop.

If I take on the home service call on an SS, I put a post it on my nose that reminds me to take a good long look to the obvious as soon as I am in the door.

The problem I see developing in the future is that, as these machines get older, the list for "the obvious" gets longer and longer especially for those machines that are sitting alone in homes with no collectors around to attend to those pesky maintenance details which demand more and more attention as time marches on.

Quoted from wbradley

Painful story, happy ending.

Hate to say it but I would have examined the area around the slingshot right at the get go as it is a lot easier than changing pins, etc.

However I commend you on your willingness to roll up your sleeves and get right into the boards/connectors...in this case unnecessarily!

In retrospect, it would have made sense to examine the area around the left slingshot first.

However, like I mention above, I've seen lots of locked-on coils in the past and the issue is nearly always related to a bad transistor, a bad connector or a stuck switch. In this case, I didn't even really give the locked-on coil much thought because there's no logical reason for a locked-on coil to affect whether a MPU makes it through the boot-up process or not. Know what I mean?

Quoted from cooke

Well, Jon, I suppose that the lesson here is that the built-in diagnostic tools in old Bally/Stern MPU's don't always point toward a board issue like one might normally suspect. The easiest solution in this case would be to replace the U10 IC and/or socket, which is what I did first.

Having repaired a few dozen of these games over the last several years, I've never encountered a problem with a MPU where the cause was neither board nor connector related. As a result, therefore, that is where I focused the majority of my energy when trying to determine the solution to the problem. .

I figured I would simply share my findings with the class. I apologize if my post got in the way of all your tech tips and helpful solutions. I'll try to remember to look first for the easiest solution to such problems in the future. Thanks for the great advice.

Sorry, didn't mean to tell you how to do repairs. I've only repaired one game from that era, and it was with your help! I was just being cheeky. These repairs in retrospect always seem really simple.

The lesson learned here is take your repairs to Cory! Oh, nd pay him by the job, not hour.  

If these repairs were easy, I guess everybody would be able to do it, but that isn't always the case.

Good post, I too would have probably leaned toward a MPU issue at first glance as well, very interesting problem....

Thanks for sharing, appreciated.
Daniel