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Repair Log… (7/4/11)


MPU4 – MOD 2


Fault diagnosis.


Slides pulse on start-up.

Slides continue to randomly pulse and chatter during operation.

Incorrect caps fitted from a previous repair. (C9-C15)

Some battery residue.


Otherwise MPU boots and runs normally, no lamp faults detected, all other aspects of the board seem OK.


Clean up battery residue with fibre-glass pencil.


First replace incorrect capacitors C9-C15 1000pF


Replace T12-T19 = BC338 (transistor pre-drives for payout triacs). No slide pulse on start-up. OK.


Slides still pulse on startup, so replace C1-C8 = 1000pf (.1uf) – Poly Cap. OK


Run board, slides remain calm. OK.


Soak test – 2 hour (short test) OK.


Battery not fitted as board is not needed at the moment.