Hello, I have two questions about my LAH.

1. The f2 fuse on the Power supply board blows on start. Now from the wiring diagram it shows that it controls the backbox lights. Its a white/green wire. well all the lights in the backbox are working. It shows this and F1 share a Bridge. Should I just change the Bridge and see if it quits blowing it?

2. I can not get the game to go into adjustment mode. It will go into diagnostic mode just fine. I have checked the wire all the way to the board connector and its good. The resistors are good on the board and from there it goes into a 7400 chip. I cant test the chip so that as far as I got. oh and the button is good.

Yes there's a memory protect switch on it and its working. It told me to open the door after I moved it and changed the batteries and when I did the message went away so I assume that the memory switch is working.

ok I changed the bridge and the fuse no longer blows. The game still functions the same though. weird... Any more ideas as to why the switch wont register?

Yes its good. I've taken wires and just jumped the header pins at the CPU and still nothing. That's about as far as I can read the wiring diagram though.

I've jumped the down switch while jumping the step button. Just goes into diagnostics.

I need someone who can read the diagram better then me and tell me what pin on what chip I can check or short to ground to see if it will trigger the switch.

anyone think it could be the NE555 timer chip that was by the batteries that does have some battery damage to it. Everything tested ok with the meter though. Maybe I should socket and change it anyway.

I changed out the 555 chip and still the same.

I changed the push button and still a no go. Im positive its on the cpu board. I just don't know where to look.

yes the advance switch is fine. The up/down switch wont register. All I have to test stuff is a Multimeter. your right it goes from the ls02 to the 6821 I just don't know how to test it or to trigger the switch on the chip itself. the manual has the pin as pin 48 on a 40 pin chip.

I'll try out the testing but ordered the Ls02 anyway. I think I should have ordered the PIA too just in case. I'm not in front of the game right now but if I remember right the pia was 11B . They have the input pin listed as 48 though so I'll have to trace that one back to the Ls chip.

I traced the path from LS02 pin 10 and it goes to pin 18 on the PIA. Pin 4 on the LS02 goes to pin 40 on the PIA. So the traces between the two are good. I have not tested voltage yet since the board is not in the game. I think I'll reflow the two chips while I have it out.

with a heat gun I removed and socketed 11B and replaced the 6821 chip. All is well now.