Pinrepair Guide:
No Flashes: the LED is Permanently On.
If you turn your Bally game on, and the LED stays on continually, this is one of the hardest problem to fix on these boards. A stuck on LED can be caused by any (or all!) of the following:
* The reset circuit is damaged (after all, it's in the battery corrosion area!) This includes transistors Q1 and Q2 (both 2N3904), Q5 (2N4403), and diodes CR5 (1N4148 or 1N914) and VR1 (1N959B or 1N4738A).
* The program ROM (read only memory) at U6 is bad.
* The ROM jumpers are incorrectly set for the U6/U2 ROMs installed.
* The U9 CPU microprocessor is bad.
* The U11 PIA (peripheral interface adapter) is bad.
* ANY of the sockets for chips U6, U9, U11 are bad.
* The ground trace to U11, U6 or U9 are bad. U11 is especially important to check the ground trace, as it's right in the corrosion zone. And corrosion just loves to travel up the ground traces. Use a DMM set to continuity to check ground at U11 pin 1 (and U11 pin 20 for +5). Also check U6 pin 12 for ground (and U6 pin 24 for +5). U9 pin 1,21 (gnd) is less of a problem as it's well outside the corrosion area.
The first and last two points are probably the most common problems.
