My Burgertime PCB has a small issue; it doesn’t want to get out of test mode. There are two switches inside the coin door to run tests on Burgertime. There are also two dip switch positions on DIP SW1 on the PCB to do the same thing (positions 5 and 6). I have verified that my coin door switches are working properly so it has to be on the PCB.
The logic is pretty simple; the DIP switch supplies power to a 74LS367AN (Chip 15C on the PCB). The voltage changes when the DIP switch is ON or OFF. The game in turn interprets a high or low voltage as being ON or OFF. With the help of a good friend (Thanks Erik!!) I first got a good grasp of what is happening here and how to test for it. Once I knew my logic was correct I did the following:
Step 1: Which IC is responsible for DIP SW1?
The first step was to trace DIP switch positions 5 and 6 to the proper 74LS367AN. I looked at the traces and discovered that 15C is where it leads to. BTW you can also read the schematic to figure this out too.
Step 2: Get some intel on a 74LS367AN
Now that I know which chip to test and which pins on 15C are the inputs my next step is figure out the outputs. This was easy to figure out thanks to a datasheet. This tells me that pins 11 and 13 are the outputs.
Step 3: Verify that the DIP switch is working
Next I needed to verify that the DIP switch was working and is supplying 15C with voltage at its input pins. With positions 5 and 6 set to OFF there is no voltage on 15C. With them set to ON I am seeing 4.8volts so I know the DIP is working and the pull up resistors are fine.
Step 4: Check the Outputs of 15C
Now that I know that the DIP is working I can see if there is a change in voltage on 15C’s outputs. I measured the voltage coming out of PINS 11 and 13. There was no change in voltage so that had to be the problem!
Step 5: Replace 15C
Let me just say that old solder SUCKS. That was the hardest time I have had trying to clear the through holes on the PCB. I got the IC out fine by cutting its pins but the old solder just wouldn’t budge. A trick I learned is to take a diode, in this case a 1n4004, and heat up the solder pad and push the lead through. I like using a 1n4004 (or 1n4001 for that matter) because it has a thick lead. I used it to push through the hole. Next I put a dab of new solder on the pad and then removed the solder with some solder wick. One of these days I’m going to invest in a good desoldering station.
Step 6: Check your work
Since I had so much trouble getting 15C out I damaged a few of the through holes. So after soldering in the SIP strips I ran a continuity check to make sure the traces are still functional. Everything checked out fine minus one particular trace I damaged and had to use some wrapping wire to fix it.
NOTE: Don’t solder late at night when you are tired. 
I admit this time I was a bit impatient and did more damage than I needed to. Also make sure you have the correct solder tip. My tip was too wide so I wasn’t able to focus the heat properly and that caused some of my issues.
Step 7: Test the game!
Here is the fun part, testing to see if you solved the problem. I put the PCB stack back together, reconnected the ribbon cables and fired it up for the first time. YAY!! It works!!
So 15C was the problem all along. Of course now I have discovered a new issue, the game plays super fast! I went into test mode and now I noticed that the game is acting like someone is holding down button 1. Looking at the schematic its another 74LS367! Guess what’s next?
Here is a summary of what I found out:
DIP SW1 – Position 6
Goes to 15C – 74LS367AN
Input – Pin 14
Output – Pin 13
DIP SW1 – Position 5
Goes to 15C – 74LS367AN
Input – Pin 12
Output – Pin 11
