Leeds
Hello and greetings from the UK.
I've been thinking for a while about building a bally lamp driver board tester for the Bally Lamp driver boards ( AS-2518-23, AS-2518-14, Stern LDB100, Alltek replacements etc.)
Up to now, I've always tested a board in a game, but the problem is that not all games use all the circuits (especially the older games) and also it's a pain opening up a working game and swapping the boards around just to test a different board.
I've got a pile of old boards, and I wanted to test then and find out what needs fixing. So, I set about designing and building a stand-alone tester - Connect it up to a board and it will test all the 60 circuits in one go, quickly and easily.
It can test each circuit one at a time and show you the SCR Number and Driver chip number, so it's easy to figure out which ones to replace if not functioning correctly.
After several months of prototyping and building, I now have a working system, and willing to build a couple more if anyone is interested. Here are the details:
Introducing the Bally / Stern Lamp Driver Tester :
Introduction:
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I got a bit sick and tired of chasing my tail when trying to figure out why controlled lamps in a game were not working, so I designed and built myself a tester:
The Bally / Stern Lamp Driver Tester, “LDT” is a quick and easy way to test and diagnose problems with the Bally AS-2518-23 (or AS-2518-14) and Stern LD100, Lamp Driver Boards found in many Solid State Pinball Machines from the late 1970’s until the mid-1980’s. It will also test modern replacement boards such as the Alltek lamp driver board. These boards can control up to 60 feature lights in a game, and have 60 separate circuits, and are prone to common failure. It is often a time-consuming job to locate the correct circuit, needing reference to the game’s schematics/circuit diagrams to locate the correct circuit. The LDT eradicates all this and quickly identified which circuit(s) is at fault, without needing to dig out the schematics.
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When trying to diagnose a problem in a game whereby one (or more) of the feature lights are not working, there are several possibilities for the cause:
1. Blown/faulty bulb
2. Corroded or loose lamp socket
3. Wiring issue: loose or mis-connected
4. Connector issue
5. Header Pin issue
6. Lamp Driver board faults:
a. Locked on SCR’s
b. Blown open circuit SCR’s
c. Faulty MC14514 Multiplexor IC’s – U1, U2, U3, U4
d. Broken traces
e. Faulty resistors
f. Cracked or non-conducting (dirty) header pins
7. Disrupted communications between the MPU board and the Lamp Driver Board
Often you can waste a lot of time going round in circles trying to figure out what the issue is. The LDT speeds up and simplifies the process by helping you identify board issues, blown SCR’s, faulty U1-U4 IC’s, cracked header pins, etc. It also ensures the J4 header connector (the one that connects to the MPU) is working correctly. The LDT will show you which of the 60 circuits are faulty very quickly.
It is a nice feeling to know that your lamp driver board has been fully tested, and, where necessary repaired to fully 100% working order. It is then easy to diagnose any remaining non, working lamp issues because you know the board is 1100% working, and so can look at issues 1-4 above.
With the LDT, a board can be tested either in-situ, without having to remove from the machine, or can be removed from the game, and tested on the bench. The LDT provides its own power source and also provides power to the Bally or Stern Lamp Driver board that is being tested, so is a complete stand-alone test rig.
Details:
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The LDT is a micro-computer controlled test system, utilising an ESP32s processor system which sends power and test signals to the Lamp Driver board, and performs a variety of different tests which enable you to quickly identify any faulty components. The main board consists of the ESP32s processor, a power regulator board, an LCD display and some drive components, along with a header connector to connect up to the lamp driver board (J4) and the 3 Led display boards. Each of the Led display boards, connects on to the relevant J1, J2, J3 header on the lamp driver board. Each board is labelled J1, J2, J3, so it is easy to identify which board should go where.
Testing – In-Situ
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There are two ways to test a lamp driver board whist installed in a game:
Using the game’s in-built lamp test:
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We can use the games in-build lamp test (in the system self-tests), to check if the lamp driver board is fully working.
1. Remove the J1,J2,J3 connectors from the lamp driver board. Leave j4 connected
2. Install the 3 LED display boards onto their named header pins
3. Connect up the fly lead to a common controlled lamp point (e.g. on the back of the insert door)
4. Power up the game and go into self-test, then lamp driver test (i.e. press the inside coin door self-test button once).
5. All the leds on the 3 boards should flash on and off. Any locked on, or non lighting leds indicate an issue, note the SCR “Q” number printed on the left hand side of each board next to each Led – this is probably at fault.
If any faults are found, remove the board to work on the bench and follow the “Testing – on the bench” procedure below.
Using the LDT Controller:
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1. Remove the J1,J2,J3,J4 connectors
2. Install the 3 LED display boards onto their named header pins
3. Install the header connector from the LDT controller to J4 on the lamp driver board
4. Power up the LDT (but leave the game switched off).
5. Follow the instructions for “Testing – on the bench” below.
Testing – on the bench:
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This is the preferred method of testing, it takes very little effort to remove a lamp driver board from game, remove two screws and unplug 4 push on connectors.
With the board out of the machine and on the bench:
1. Install the 3 LED display boards onto their named header pins
2. Install the header connector from the LDT controller to J4 on the lamp driver board
3. Power up the LDT.
4. Perform the 3 tests: “Lock on”, “Auto SCR” and “Single SCR” tests. These are described in detail below.
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Power Up
On initial Power the LDT controller will display an opening message on the LCD display, along with a version number. After a second or two this will disappear, and a message asking you to press start for the next test.
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Lock On Test
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The first test is the “Lock On” test, Press start to commence the test. The system will apply flashing power to the board, and any faulty circuits that are “Locked on” will show up, as their corresponding LED will flash. For a perfect board, no LEDS should light at this stage. If any Leds flash, note the Q number which is printed on each LED display board to the left of each Led.
Locked on issues are normally caused by a faulty SCR which has short circuited, so test or replace the SCR’s you have identified by their Q numbers. All SCR’s on the board are clearly labelled with their Q number. It is sometimes possible to get a faulty drive chip (these are the MC14514 IC’s at U1-U4). It is much easier to replace a 3 pinned SCR, rather than soldered in 24-pin IC, so I generally replace the SCR first, and if the problem persists, it’s more likely to be the IC.
All locked on issues should be resolved first, before carrying on with the other tests.
Press Stop to move onto the next test:
Auto SCR test
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Test 2 is an automated run through each of the 60 lamp driver circuits, starting on J1 , pin 28 down to pin 1; then J2 pins 23 down to 1 then, J3, pin 27 down to pin 1 (note there is no led connected to pin 28 on J3).
This is a very quick way to spot any non-working circuits. I use it to quickly spot any circuits that are not working.
The test can be repeated as many times as you like, or move onto:
Single SCR test
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Test 3 is an individual step through test of each circuit. the Fwd (Start) and Back (Stop) buttons are used to move to the next or previous circuit. The LCD display shows the Q number of the SCR as well as the chip number and pin output, these are all needed to easily and quickly fix and non working circuits. The Q# is also printed on each led pcb next to the led.
This is the most useful test because you can step through each circuit one at a time and check they are working. For any non-working circuit, you are presented with all the information you need to further diagnose the issue, the LCD display shows:
• SCR “Q” number, so you can check out (or just) replace that SCR
• The IC Number, U1 – U4 – If you get a lot of non working circuits, that all relate the the same U IC, then you can probably assume it’s an issue with the IC or the signals to / from that IC.
• The IC Pin number – which output pin of the U1-4 IC is responsible for this circuit. Use a logic probe to test to see if that pin is correctly switching to high from low when the circuit is activated.
• The IC Logic output #. The MC14514 IC’s each take 4 inputs and convert into a binary multiplexed output 00-15, 15 is not connected to any lamp circuit, so 00-15 gives 15 lamps circuits that each IC can control. 4 X 15 = 60 circuits in total. If several circuits are out and they are all on the same logic output #, then suspect an issue with the control signals – usually a cracked header pin on J4.
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To exit the tests, either press Fwd at the end of J3 (Pin1) or press Back at the start of J1 – (Pin 28), you can either repeat the tests, or the system returns to test number 1.
You can switch the tester off at any time.
Other information
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I will be making a limited number of these for sale, each item will be fully built and tested and will include the wiring connectors to connect the controller to the lamp driver board J4, and the common feed to the 3 led display board.
For UK customers a UK plug power supply is provided. (for overseas customers, please provide your own DC power source. (You can use the on-board power jack (centre positive), or can connect directly to the inputs of the power regulator board – the power regulator is capable of receiving any DC voltage from 7-30v, it then converts this to 5v required by the tester and the lamp driver board.)
Easy Software Updates
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The system comes with built in Wi-fi to enable easy software updates OTA – “over the air”.
As the software evolves (from other user feedback) and we add more tests or better features, we need an easy way for you to be able to update the firmware. I will make available a file for download that can be uploaded to the tester, using a laptop, tablet or phone.
The LDT created its own Wi-fi access point, and connecting your device to this, allows you to perform a firmware update.
Next Steps
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I will be making a small number of these towards the end of this month / early May. Price TBD but around £125 GBP + Shipping, based on parts costs and the time to build and test each one.
Open to suggestions on how to improve in future. I could also expand it to test other Lamp drivers, eg the two aux driver boards (although in my own experience these seem a) more robust and b) far easier to fix, compared to the main LDB.
On a final note. I used this tester to test, diagnose and repair 7 or my 8 broken Bally & Stern Lamp Driver boards, many had faulty SCR's and 4 boards also had blown MC14514 IC's, requiring removal, socketing and replacement. The tester helped my easily and quickly figure out which components to replace in each case. The 8th board durned out to be beyond economical repair, many of the signal traces around the pcb had been completely eaten away by acid damage (I guess from a leaky MPU battery above!). I could repair it but it's never going to look pretty!
Thanks for reading, best regards,
Alan
YOUTUBE video of it in action
PS More images:
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Chesterfield, MO
Boucherville, QC
