Robotron RAM Issue

eb94110

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I have a weird issue going on with my Robotron.

Yesterday the monitor was recapped. When I started to play it again, the sound was going in and out and then stopped. I hit the reset on the main board, not realizing in the past when I had this issue, I had hit the reset on the sound board, and things were fine. When I hit the PCB reset, the screen went red. It said 131 error.

I tried to move the RAMs, and I still got the 131 message. I then moved around the connector on the upper left of the PCB, and I got a rug pattern now with a 111 RAM error. After moving that connector again and resetting the PCB again, I got this image.

@braedel did a great job rebuilding all these boards and p/s in the past two years. I can certainly check the p/s, but I wanted to ask if anyone had any other thoughts on what this might be.

Thanks so much.
 

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you have a ram data line issue now. that's what the red lines are from.

pull ram 11, make sure the legs are straight. start there.
 
131 Error Code - Decoded:
  • 1-3-1 | First digit indicates error type
    • 1 = RAM
    • 2 = ROM
    • 3 = CMOS
  • 1-3-1 | Second digit indicates Row (Bank) number (1, 2, 3) - Bank 3
  • 1-3-1 | Third digit indicates position in row (1 through 8) - Position 1
When the system is powered on and before the game code is loaded, it first loads and runs a RAM test, then ROM test, then checks the CMOS. These are essentially different programs, or 'apps'. Once they all complete successfully, the main 'Game Program' is loaded and executed.

The downside to the RAM test is it test location 131 first. It's very easy to see this result and assume the RAM in that location is bad, but typically this error indicates other larger problems with addressing, moving data in/out of the RAM, etc. The best way would have been to have a routine or message where if ALL RAM test bad, it lets the user know 'All RAM Test Bad - Check Common Components' or something like that.

The most common cause of a 131 error is typically when one of the 3 required voltages is missing, or wrong on the RAM (+12v, +5v, -5v). Always start there.

~Brad
1753387176257.png
 
Thanks so much, @braedel. That's great to learn.

Now off to figure out the sound issue.

Thanks again.
if you still have the IDC plugs on the green wire harness between the rom and sound boards you might have a wire coming out. though that doesn't make sense why you would lose all sound. as far as I know the "handshake" isn't used. at worst you would only lose a sound line.
 
Thanks @mecha and @braedel, I appreciate the help. If I push on the connector, the sound comes back. I am guessing the contact might be getting lost in some way?
it's probably the plug, but if the sound board hasn't been gone through then maybe solder to the header pins is cracked.
 
it's probably the plug, but if the sound board hasn't been gone through then maybe solder to the header pins is cracked.
It could be the plug.
It could be a cracked solder connection on the PCB at the pinned connection.
 
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