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.

 

Repaired.