Getaway

[bones]

Had a look at a Getaway pinball for someone and after replacing the general illumination plug which had melted to the PCB and having to put new pins in the PCB it all came back OK,my only issue is that all the bulbs on the red blue line in the lamp matrix are not working. I tested the transistor in circuit and it appeared OK but I seem to remember that this is often the case and it really needs to be out of circuit. With the lamp matrix bearing in mind all other lamps are working correct is it liable to just be the driver transistor or is there anything else I should be aware of. PS I was only supposed to be giving it a clean a few new rubbers and change a few non working bulbs

 

[t-m]

Well you’ve got a ls374 driving a transistor that in turn drives a triac for the GI.
Check the ls374 output and the transistor it drives, the triac is usually reliable (although never say never!)

 

[bones]

Thanks for reply, I managed to find some schematics for the lamp matrix and it indicates that the red/blue is considered a row as opposed to a column. Am I right in assuming that apart from discrete components the circuit(ignoring the input from the CPU) there is only a 74ls74,a tip102 and a lm339 to be concerned about? The column side appears to be a lot more complicated.

 

[t-m]

That will teach me to reply late at night as I thought you were talking about GI not the lamp matrix.

Yes that sounds right, it's probably the transistor but you can test it. Some useful test info here.

 

[bones]

Thanks that's a nice link, I'm looking at this for someone who is some distance away so I'm limited to what I can take with me,I'm gonna take a 74ls74 a tip102 and a lm339 but humour me here could I just snip the red blue cable and connect it to another working row briefly when in the all lamps flashing test? As long as I disconnect the original wire from the row I'm using it wouldn't overload it. I think the red blue was row 7 so I was thinking of switching it with say row 6 which I know is good. Can anything bad happen doing this?

 

[t-m]

Nothing bad will happen but I would check the transistor first before swapping wires