Repairing an MPU4 board is a logical process of elimination. You start at the beginning
and diagnose the fault. When you first look at the PCB above you will not have the
faintest clue where to begin, but with a little patience and time you will begin
to understand what the different parts of the MPU do and how you can repair a fault.
There are 2 ways to repair a board. The first is to roughly know which part of the
board is at fault and change the part or to diagnose the fault using a multi-meter
and/or logic probe or a combination of the two.
Everyone has their own preference for soldering and parts. I would say use a temperature
controlled iron with a point tip at 400 degrees C. Use lead solder not that lead-free
stuff. Get some good Servisol solder-mop for soaking up solder. Some good turned
pin strips for your ICs. You need a good light source, a fibre glass pencil with
refills. That’s probably enough
to get started. Parts can be obtained from ebay and various other suppliers.
Let’s not beat about the bush, you just need to know which part to replace and where
to get it? I’m with you on that one.
I’ve created a flow chart to get you off the mark.
Sniff out that bad transistor with the booze.net bad transistor sniffing out loom.
Just get yourself some PCB strip board from maplins and some 8 switch dils and cut
the blue loom in half. Wire each through each bank of the DIL switch. You can then
switch each transistor on and off as required. No more time wasting with the meter,
you know which one is bad the moment it alarms. Green plug is next and the triacs
also. DIL switches are cheap and very neat. Also nice to PCB mount, remember to cut
the tracks horizontally across the switch or you’ll be forever closed)
The buzz from fixing your own fruit machine cannot be over stated. It’s like nothing