Repair Log… (23/5/11) - MPU3
Power up - Nothing!
Test 5V which measures 3.3V. It's not going to boot. Discuss with Magik, he suggests
replacing D44 and D45, but I don't have anything that big diode-wise.
Re-test 5V. The test points are covered in corrosion and some battery residue. Clean
up test points.
5V OK now. This board has a RAM converter board which I’ve not seen before.
Then I notice T60 is broken, replace T60.
Remove T59 and R79, for manual reset. Jumper wire between R and 0v test point, something
happens, but not a full boot, it's getting stuck.
Jumper R and 0v with wire, board boots into attract.
That'll do for now it runs.
Test 5V measures 0V. Not good, it's never going to run. Where has the 5V gone?
Remove white plug to inspect, notice a bent pin on the MPU3 which has pushed a pin
out of the machine plug.
Straighten pin, plug in white power plug. Test for 5V. (5V is back, this is happy
moment for me!)
Remove T59 and R79, for manual reset. Jumper wire between R and 0v test point, no
joy, still no boot. (Slight shudder from reel deck)
Test RAM voltage at pin18. Measures 3.2V. Not good should be 5V. RAM voltage is too
low, but why?
Replace T60 and T61 something happens, it's gone a bit mad. Lamps are flashing, reels
are jumping. It's not happy though, it's still not right.
This board wants to live, but something is stopping it coming to life...
Processor address lines are pulsing, RAM is pulsing, it should be running. Test RAM
voltage again, still 3.2V.
Magik suggests testing RAM voltage without the RAM in the socket... too late though
I've already replaced it.
That's the third one running!