Flash Gordon was working well with one error. On the playfield inserts for the upper playfield bonus, the playfield lamp under the number nine would never turn on and the number ten was locked on and would turn on with the GI.

This morning, i entered the self-test by pressing the button inside the coin door. I had never tried the self-test and wanted to see if it would shed any light on the locked on insert lamp.

I pressed the button and it entered the test. The number nine did not light and the number ten stayed lit and would dim when the playfield lights flashed. I continued through the test and cycled the power.

Now, the alltek mpu self-test light only flashes five times. The playfield and backbox GI are on, but the displays do not come on. When I turn it on, the power on siren sound continues for about a minute and then goes off.

Ive looked up the significance of the five flashes and found this:

Fifth Flash:
Tests the second PIA chip (U11). As above. If you have already swapped U10 and U11 and don't have the fifth flash, try a new 6821 in U11. If still no success, swap once more. Worst case-replace both PIA's.

Sixth Flash:
Tests the Display Interrupt Generator. This actually tests both U11 and U12. If U11 has been replaced, and no sixth flash, replace U12.

Does five flashes mean it is failing the fifth test? Need to replace the U11 chip?

Thanks in advance for reading this.

Followed a suggestion that I check fuses - I know I'm new and not great at diagnostics. I found that F4 was bad. I replaced F4 and did it blew shortly after power on. Where does the diagnosis go from here?

I unplugged the connectors to the driver board. The fuse did not blow.

Before I forget, thanks to everyone for taking the time to help me through this.

Barakandi, interesting you mentioned the knocker coil. This machine is fairly new to me and I don't think I have heard the knocker fire even when a new high score was set.

Since I can't get into test and I have everything disconnected from the driver/power board, how do I test the coils? Physically inspecting that there is no frozen coil?

None of the coils seems to be physically bound. I checked the coil in the coin door and the arm it hits could have been out of place.

Should I begin restarting while adding one connector at a time to the driver board to try to isolate the problem location?

I hooked up the connectors expect for j2. The game goes into attract and will start a game. When j2 is connected, the fuse at j4 on the rectifier board blows.

I clipped the line to the knocker and now everything is working, except the knocker of course. Going to get a new coil for the knocker and see if I can get it to work.

Thank you for all the help.