Open the backbox. On the MPU board there should be an LED that flashes when you power it on. How many flashes are you getting?? The below information may help. It may be as simple as reseating the chip.
How to Count Flashes.
When the CPU board is initially powered on with the diagnostic test EPROM, the PIA LED will immediately turn on. This is considered the first "flash" (many people think the first darkening of the LED is the first flash, but this would mean there was only a total of seven flashes, not eight). Just keep this in mind when referring to the flash codes listed below.
The completion of a flash means the associated chip has passed the diagnostic test. For example, if the LED turns on and stays on (never turns off), this is considered the first flash (and hence, the EPROM at 5C is faulty). If the LED turns off four times then stays lit (the fifth flash), chip 11D would be bad.
Flash Position Item Tested
----- -------- -----------
1 5C/5B EPROM checksum error
2 5D RAM read/write error
3 5F PIA1 solenoid read/write $2100
4 8H PIA5 switch read/write $3002
5 11D PIA2 lamp read/write $2402
6 11B PIA3 display2 read/write $2802
7 9B PIA4 display1 read/write $2C02
8 7B PIA6 sound read/write $3402
</PRE>
</PRE>