While I wait for answers about my
questions on the AC leakage from the power supply capacitor. I thought I would turn my attention to the main processing board. I just got a new testing tool, an Atlas DCA55 which says it is easy to use. Just connect it and it figures everything out.
I tried checking the diodes but it is unable to test them while in the board. I'm not ready to unsolder every component and check it yet, so I turned my attention to the transistors.
I checked the first one, and it shows "transistor" and that all is good!
The second one says it is not a transistor but is in fact a diode network...hmmm
with the third one we are back to a transistor again and it is ok.
It thinks the last one is a LED or diode...bizarre
According to the schematic and parts list the bottom 3 are supposed to be the same transistor and the top one is a slightly different transistor. So I guess I will have to unsolder #2 and #4 from the board and check them isolated, it is possible the board connections are messing up the reading.
edit: the manual specifically says it cannot check transistors while in circuit....before i start pulling things off the board at random i think i will look around some more.
While checking the transistors, I noticed the board has a lot of corrosion:
Apparently this is pretty common as the battery they used to store the high scores leaked acid vapors over the years.
After looking around some more it is apparent this board has already been repaired once:
the battery has been removed and the area around it looks to have been sanded down (presumably to remove the corrosion) and even a wire was soldered in where a board trace had failed. So hopefully all of those fixes are still good!
No comments:
Post a Comment