(Topic ID: 24211)

Repairing Williams Sys 3-6 Master Display Board - a Shotgun Guide w Pix (long)

By viperrwk

6 years ago

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  • 16 posts
  • 9 Pinsiders participating
  • Latest reply 1 year ago by Willillist
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    #1 6 years ago

    I see lots of posts about Williams 3-6 displays and the problems people have with them. I’m in the process of fixing up my Flash and thought I would share what I had to do to get my trashed master display board (MDB) working again. I figure if this board could be brought back to life pretty much any board could be.

    A lot of this info is already out there in the guides and on Pinwiki. If you search it you will find it. I don’t claim to know everything – there are many smarter people than me in pinball. I just figured there should be a place on Pinside for this info.

    The System 3-6 displays are simple devices. Some of the problems people have with them stem from bad high voltage at the power supply or bad connectors to the MDB at the MPU board. You need to take care of these issues first before tackling MDB problems. Also, issues with the slave displays are related to the MDB which if addressed will solve the slave problems. However, some slave displays are either outgassed or have bad solder connections because either someone hacked it previously, the double sided tape dried out or all of the above. But if you address power, connections and the MDB, you’ll then know if your slave displays are an issue or not. I’m not covering any of that here – find it in Pinwiki or a guide.

    First, some before photos:

    This is what I had to start with – no this board did not work – I had nothing when I turned the game on. And no, the white wires are not factory jumpers. Somebody worked on this board previously and tried to repair damage that was done to the traces in a way that was, to put it nicely, less than elegant.

    You can also see the mix of old and new resistors in the upper right corner. As Clay and Pinwiki point out these 10K resistors are known for going open and obviously some of the original ones on this board did and someone replaced some, but not all the resistors. That makes no sense to me. These are 30+ year-old components that have seen hundreds if not thousands of hours of use. If you’re going to replace one resistor that has failed, why not all of the same resistor? How long before the next one fails?

    Same problem here – some of the resistors have failed and have been replaced with 1/4w instead of 1/2w resistors as you can see from their smaller size. This is just a recipe for further failure since these resistors are stressed to begin with and with only 1/4w rated resistors in there they can’t handle the load for too long. Plus these jumper wires will have to go and the broken traces will have to be addressed.

    You can see where the display is soldered to the board that someone lifted some of the soldering pads off the board – probably by using a 150w Weller soldering iron or some such. If you’re thinking about doing that, don’t! This will be the result. The traces and pads on these boards are old and too much heat will just damage it further.

    You should also notice that this display is not attached to the board. The double-sided tape that holds the two together has dried out – a common problem. Many people try repairing that by folding duct tape into a loop and trying to stick the board back to the display. Some people don’t even bother and just let the board hang by the connector. Both are bad things to do as neither solution is good for the solder joints – ugh.

    Well, it’s on to the repairs.

    #2 6 years ago

    First thing I decided to do is remove the display and all the resistors from the MDB. I want to remove the display to clean the glass and board from any residual tape so that I can use new double-sided tape to properly mount the display.

    I want to remove all the resistors because I’m going to replace them all with new ones so I won’t have any problems with any old ones going open. If you have missing digits or segments on displays, the resistors can be the problem. They obviously were on this board and best thing to do is just replace them all.

    I have an old Radio Shack temp controlled soldering iron and a Hakko 808 desolder that I use for all my electronic repairs. These tools have worked well for me. I wouldn’t call myself a master solderer – sometimes it’s not the prettiest job you can ask for but I usually don’t lift traces or damage boards. I did enough of that in my younger days. The most important thing is a temperature-controlled iron. You’re least likely to do damage with that. A solderpult is also very useful. Other tools to suck solder are advised. Solder wick is not. I won’t get into the debate about which works best. Save that for another thread.

    I desoldered the leads on the display to remove it and two things happen: more mounting pads come off the board, likely loosened when the last person worked on the display. And then I notice this with the display leads:


    I can move the leads inside the display and make the tabs touch each other. That’s not good. I suspect this was done when someone took the Weller to the board and they heated the leads so much that they detached from their connection. If I pull hard enough I think I can pull a lead out entirely. Ugh again – I’m going to need a new display glass.

    I proceed to remove all the resistors – both the 10K and 3M ones from the board and notice that one of the traces from one of the resistor mounting pads to the 7180 was damaged where the jumper wire was. Ugh x3. Another one to fix.

    Pulling the display and resistors exposed the problems with the existing display and traces. If I was using the existing display it would have made it easy to remove and clean the tape from it as well as clean up the board. Another benefit is that it allows you to also check the 6184s and 7180s effectively. Which I did following this procedure outlined on PinWiki: http://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#Master_Display_Drivers_for_System_3_to_6. If you leave the glass in and it is shorted, you may get a false reading on the 6184 test. As it says in PinWiki: "A shorted display glass can show up during the UDNxxxx 11 through 17 test." So without removing the glass, you won't know if the problem is the UDN chip or the glass itself.

    Once I completed the testing, it was time for Ugh x4.

    I suspect with the bad leads in the score glass, the old display somehow shorted and as a result took out one of the 6184s which tested bad. Guess I’ll be needing one of those.

    My needed part tally:

    Double-sided tape
    14 10K ohm 1/2w resistors
    5 3M ohm 1/4w resistors
    1 18 pin DIP socket
    1 6184/6118 transistor array
    1 six-digit score display glass

    The resistors and DIP socket are cheap and easy. Our good friend Ed@GPE has these. The resistors are $.05 each with a minimum purchase of five of each required. That’s about $1 in total to replace all the resistors on the board.

    The DIP socket is another $.50 so we’re up to about $1.50

    The 6184/6118 is a bit tricky. As Ed states on his site:

    “BEWARE! The UDN6118A and UDN6118A-1 transistor arrays are heavily counterfeited. Allegro stopped making these in February of 2002. Easiest way to spot counterfeits - always look at the four digit date code on the second line. The Chinese counterfeiter's -love- to provide seemingly new parts to customers so the date codes always reflect relatively recent dates on them. If your date code is higher than 0210 (10th week of 2002) -- you can be assured that the part is counterfeit.
    Also beware of sellers providing parts with a "-2" suffix. These are the low voltage version of the 6118 and have an absolute maximum rating of 60V. Only place these will safely work is on a Gottlieb 4-digit display.”

    You see these all over ebay. Do a search on “6118 IC” and you’ll see all these counterfeit units being sold from Hong Kong/China. If you buy one of these be prepared for fireworks. You have been warned.

    Ed does sell a replacement – the uPA6118C from NEC for $5. The only issue with it as Ed states:

    “Note -- these are identical to the Sprague UDN6118A's but have a lower breakdown voltage than the UDN6118A-1's. If using this in a Williams display driver application that requires the UDN6118A-1, make sure the voltage at the display driver is below 85 volts. Often these machines use a 1N4764 to derive 100Volts. This 100Volts is then reduced by an addtional 10 volts on the display driver board to provide 90 volts to the display. It is recommended to replace the 1N4764A with a 1N4763A to reduce this voltage to just under the 85 volt threshold.”

    This means that in order to use this part on the MDB, you have to lower the voltage on the power supply for the displays. This is always a good practice to extend the life of the displays. I’m planning on doing that on my Flash anyway BUT, I didn’t want to have a display board that potentially would be swapped out down the line into another machine where the HV was factory standard. Not only that, you may have some displays that won’t work at a lower voltage so this solution may not work for your machine.

    There are NOS 6118s out there to be had but they are starting to get scarce. I wound up ordering a few from Robert @ twobits.com. Cost is $5 + shipping.

    Here is the new 6118 installed in a new DIP socket. Notice the date code of 9741 which identifies this as a legitimate part.

    Now I’m into the repair for about $6.50 in parts + shipping but I still have one problem left – I need a new display glass.

    I could get one from Steve Young @ PBR – he sells new ones for about $59+shipping – less if I bundle my order and get it to $100 for the 10% discount – but that’s just a little too rich for me.

    I see that jewboyflowerhead posted that he had Williams Sys6 displays. After some checking on his end, he sells me a working display for $10 – an ideal alternative. And he happens to be a great guy to deal with and a great Pinsider.

    There was one problem with the display he sent me, which wasn’t really a problem at all. The display was on a slave board (player display) and once again the double-sided tape was dried out. Perfect! This saved me the trouble of having to pry off the display from the tape/slave board. All I need to do is desolder the display from the slave board and clean it up. The good thing is that the six digit displays are mostly interchangeable with each other, as long as the leads on the display are long enough and haven’t been cut too short, so it was fine this display came from a slave board.

    For $16.50 in parts I now have everything I need to fix the MDB.

    After installing the new 6184, I install the new resistors. I actually put 1/2w rated resistors for the 3m parts instead of 1/4w – it’s overkill but there’s no harm in doing so.

    As I install the resistors I clip and save the excess leads. The reason I do this is to use them to fix the broken traces like this:


    Here’s the repair for the trace from one of the 10K resistors to the 7180. This is a common method to repair broken traces. There are other more sophisticated ways to do this but for this application this is fine.

    Post edited by viperrwk : Added PinWiki link for testing UDN6xxx.

    #3 6 years ago

    To fix the missing pads on the board I have a through-hole repair kit that I bought from BEST:


    It’s not cheap, but it’s the easiest way to correct the butchery. I won’t go into how to repair the through holes here as there are videos online that you can get to from the BEST site that show how to do it.

    Before mounting the display, I clean the back of the glass and the side of the board it mounts to with Goo Gone to make sure there’s no residual adhesive then clean the glass and board with Windex. I put double-sided tape on the glass but don’t expose the other side until the glass is fully soldered to the board in case I don’t have the display lined up perfectly or a lead is too short to be soldered in as I don’t want to peel the glass off the board once I put it down.

    In addition to repairing the back of the board, I also have to jump from two mounting holes for the display leads to the traces above. To do this I use a xacto knife, carefully scrape off the green screen on the trace, and then use one of the snipped leads from the resistors and solder it to the trace similar to what I did on the back of the board. The other end I stick in the hole with the lead from the display and solder the two of them together in the hole.

    Then it’s time to do all the soldering. It’s a total of 92 solder joints to put it all back together.

    Photo_7.jpg Photo_8.jpg

    Here’s the finished result – front and back. Now it’s time to test. I’m putting it in my Firepower (for sale - http://pinside.com/pinball/forum/topic/fs-firepower-central-ct) which has a modified HV PS since I haven’t worked the PS on Flash yet.

    When I first put it in the machine to test it, I only hook up the power and data cables. I don’t hook up any of the four player displays just in case something is wrong (which I don’t expect there to be.) I don’t want to damage any good player displays in case of a malfunction.

    #4 6 years ago

    Run the display test, make sure all the digits/segments show up, then shut off the machine.

    Feeling lucky, I hook up all four player displays and turn the machine on again. Volia! Everything works the way it should. And the best part is that it all works on a power supply where the voltage for the displays has been reduced.


    What did I miss?

    What I described here is a bit of a shotgun repair since I was replacing some components that were probably functioning. Most of the components on the board were either replaced or checked so I knew they were functioning and I fully expected it to work when I hooked it up.

    I didn’t touch the three 14069 hex inverters on the right side of the board or the two 14543 decoders. If when I first plugged it in and turned it on and I was missing a digit on the MDB, but then plugged in the player displays and they were all good, the hex inverter at the bottom right of the board would need to be replaced (another $1 for the inverter and a DIP socket.)

    If there were digits missing on player displays 1 & 3 when I hooked them up, the middle 14069 would need to be replaced and if displays 2 & 4 were missing digits than the hex inverter on the top would need to be replaced.

    However, if the credit display and player 1 and 2 were missing digits, then the 14543 decoder on the right side of the board would need to be replaced (again another $1.) If player 3 & 4 were out then it’s the decoder on the left side of the board needing to be replaced. Again this all assumes you tested the 6184/6118 and 7180s while the resistors and display glass was out and they were all good.

    This was my fourth board to repair and it was by far the worst. But I’ve been lucky and the only thing that has been bad so far are the display glass, resistors, or a 6184/6118. I’ve not had more than one 6184/6118 fail on a board. I suspect once it does the game doesn’t get used and no further damage is done. Save for the display glass and the 7180s, assuming you have to change the resistors and a 6184, it shouldn’t cost you more than $15 in parts and shipping to repair one of these boards.

    What about the display What about the 7180? What if one tests bad?

    If a display glass is bad, you have to get either a working used or new one. Expect to pay at most $65 for a new glass. If you get a used glass and need to test it, you can either hold the display up to a plasma ball and see if any of the segments get excited. Another method is to carefully line up the pins on the old display with those on an installed working display and see if it lights up.

    If the 7180 is bad, that’s a big UGH. The good news is they are still available from Arcade Chips:


    The bad news is that they are $20 each! Plus shipping.

    The worse-case scenario is if you have a bad display glass and bad 7180 and have to buy new of both. Throw in the resistors, DIP socket, double-sided tape and shipping and you are probably looking at $100 to restore a MDB – plus your time to do all the work. By comparison you can buy a brand new X-Pin display set for $200:


    Assuming your player displays are all good you could easily get $10-$20 per display which would lower the cost of X-Pin to about $120. The difference is a little more if the problem is a 6184 instead of a 7180. It’s up to you how much you value the original plasma display.

    I hope this helps someone the next time they come across a display problem. I want to thank Pinwiki, Clay, folks on RGP and folks here at Pinside for all the info they’ve put out there over the years. These displays are easy now for me and I hope this helps make it easy for you.


    #5 6 years ago

    Nice writeup.

    The kit from BEST looks like a good buy. I've been using eyelets from International Eyelet and have found them to work very well - I may make the investment soon!

    5 months later
    #6 6 years ago

    This is an excellent post. Thanks kindly for taking the time to document all this so thoroughly

    One question I have - you wrote 'And the best part is that it all works on a power supply where the voltage for the displays has been reduced.'

    How is that done?

    #8 6 years ago

    Nice write-up. Thanks for taking the time to put it together.

    #9 6 years ago
    Quoted from Wizcat:

    One question I have - you wrote 'And the best part is that it all works on a power supply where the voltage for the displays has been reduced.'
    How is that done?

    To answer my own question, seems this is documented via pinwiki: http://www.pinwiki.com/wiki/images/5/59/PSU-Display-PWR.pdf

    In summary, replace the 100v zener diodes on the power supply board, with 91v zener diodes. Will be trying this soon myself

    #10 6 years ago

    Nice description, and good pictures!

    #11 6 years ago

    good info!

    7 months later
    #12 5 years ago

    Viper, Is there a continuity test or some other electrical test to determine if a display glass is good?

    The Wiki and you mention lining up the pins from one display to the other. You line up the questionable display over a working display? Have you tried this? Seems dangerous and the risk of shorting pins is high. What happens if the pins short? Do I do that over the master or one of the slaves?

    I'm looking for a basic glass test without having to touch parts with 200V potential (-100 to +100 = 200v). This makes me nervous!

    #13 5 years ago

    Viper, Is there a continuity test or some other electrical test to determine if a display glass is good?
    The Wiki and you mention lining up the pins from one display to the other. You line up the questionable display over a working display? Have you tried this? Seems dangerous and the risk of shorting pins is high. What happens if the pins short? Do I do that over the master or one of the slaves?
    I'm looking for a basic glass test without having to touch parts with 200V potential (-100 to +100 = 200v). This makes me nervous!

    Good question. I should cover off a few troubleshooting tips related to the display glass.

    If the display glass is still installed, first check your voltages - specifically +/- 100v at the power supply. If you have the correct voltages there, the display should glow when the machine is on even if no digits show. If not, check to make sure you are getting the voltages to the MDB. You can check the voltages at the points noted in the photo.


    If you get the voltages at the test points, shut all the lights off and see if you notice the glow. If you don't, check for +100v at pins 6 and 34 (pin 1 is the rightmost pin under the ones digit) and -100v at pins 7 and 31 (these are the keep alives.) If you have voltage but no glow, the glass is bad and should be replaced.

    If the glass is not installed, you have two options.

    If you have a plasma ball, hold the pins up to the lit ball and see if any of the display segments light up. If they do the glass is good. If none light up at all, the glass is bad.

    The other option is to touch the pins to a working display. Yes, you have to line them up carefully and try not to short pins together but if any segments light up when you do this the glass is good.


    #14 5 years ago

    Thanks for the procedure!

    3 years later
    #15 1 year ago

    This thread has been super helpful I'm hoping for a little more help if possible.I am repairing a master display that is completely out but all slave displays are on and working fine. I have +100 and -100 at the test points on the mdb but not at the pins below that glass what should be my next step and figuring out where my voltage went?(first display repair sorry)

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