Using flippers resets the machine. "The BR2 problem" (again) (not)
Bought My TZ in July 2000 and within 12 months was experiencing reset
problems. I replaced BR2 and added tracking wires to C5 and the problem went
away.
A few months ago the problem came back but as it only gets a few hours a
week use I didn't think it could be BR2 again. I've deliberately left it to
get really bad so that I can use my cheap Epay oscilloscope to find out what
exactly was wrong. This is what I found.
1) Pressing either left or right flipper buttons between 1 to 3 times causes a reset
2) Pressing both flipper buttons simultaneously always causes a reset.
3) Ball search never causes a reset.
4) Flipper test in diagnostics never causes a reset.
5) Removing DMD produces no improvement.
Test procedure
1) Monitor 50V (TP6) on power board. Looks okay*, although noisy, no drop of voltage when reset occurs.
2) Monitor 5V (TP2) on power board. Looks okay*, although noisy, no drop of voltage when reset occurs.
3) Check zero crossing signal (TP4). Looks steady with no changes during reset.
4) Check reset pin 1 on U10 MC34064 on CPU board. Pin was flicking low during reset. This indicates that the 5V rail is dropping when the flipper buttons are pressed causing the reset.
So now we have a problem, why is the 5V on the power board not dropping but U10 is detecting a drop and so resetting the CPU?
5) Check CPU 5V by monitoring +VE side of C31. Was 4.7V* dropping to 4.5V* when reset occurs.
So this confirms why U10 is correctly firing a reset but why is the 5V line on the CPU board low?
6) Removed and inspected connector J210. No problems found. Reconnected.
7) Check CPU 5V by monitoring +VE side of C31. This was now 4.9V*
8) Started game, pressed both flippers and no reset and no problems since!
So all it was this time was a dirty power connector J210 on the CPU board. Didn't even have to manually clean the contacts, removing and reconnecting it was enough. Probably worth doing this to the other end of the cable, J114 on the power board as well.
so...CHECK THE EASY THINGS FIRST!
*Quite hard to measure an exact voltage on an old analogue oscilloscope!
I'm really pleased that with ten minutes investigation (using a £40 oscilloscope) I've saved having to replace BR2 again and the only problem seems to have been a dirty connector.
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