View Full Version : JAMMA stress out

22nd July 2006, 12:57 PM
Did a bit of work on my cab this morning. Something I have been planing to get around to for a while. It has always shitted me that northing was wired to video ground, and only one side of the power connectors were wired (1+2 were wired but A+B not, etc).

So I fixed this. At one point, I accidentaly got a bridge of solder between pins 3 (ground) and 4 (+5V). I fixed this, but when I was ready to test, got paranoid. So I did a continuuity test accross 3+4. BUZZZZZZ! WTF? Spend a few minutes staring at the gap between 3+4. Test again. BUZZZZZZZ! Come On! You could drive a buss through this gap. I didnt want to plug it in in case it really was an invisable short. Well, there was only 22 ohms resistance.

What to do?

I then guessed that the 'short' may be the AC to DC conversion curcuit, when it flips the polarity for the negative cycle. Hmmmm....nope, still not willing to plug that cord in.

I then remembered the JAMMA cocktail ! I test there...BUZZZZZ...22 ohms.

So lesson is that there will be always be a positive continuuity result across 5V and GND on the JAMMA connector. Weird, but true.

22nd July 2006, 02:05 PM
might be worthwile adding to the power supply faq?

23rd July 2006, 10:58 AM
if you want to check a harness for shorts, you need to disconnect everything on the other end :)