Re: F-14 SIP resistor network? or transistor?or faulty diode or short in the white/brown wire strain?

"Pinballed" <probassace@xxxxxxxxxxxx> wrote in message
news:ed2cc8a4-3559-4d39-aaf3-9e874959100d@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
First of all, I have done ALOT of reading in the archives and I'm hip
to the SIP resistors as one of the main culprits for this problem.
Random tilts. I've replaced a couple already. I replaced SR 3 because
the values were out of spec. I replaced SR17 because pin 9...I think,
cant exactly remember right now...read about half but then after I
replaced it and noticed it was the same, in Marvin's guide, I found
where it says that one pin in SR 17 reads as such. D'oh.
Anyways, with the board out, I tested the rest of the SIPs (again) and
they're bang on. I think I would be replacing them just for the sake
of replacing them only to have the same problem and chance damaging my
board with all the soldering and desoldering etc.
The main problem maker is the left sling...very common for this
machine it seems. Its on the w/bn wire. As is the top left T, the 3
target, bottom left T, pf tilt and slam tilt...and one other on that
strain, I forget right now. So I seperated that switch under the sling
just to see...now it wont tilt when it hits the sling...naturally but
it still will randomly if you hit the T's and the 3 etc...basically
the rest of that wire's line up. Naturally. I expected that too. This
is all as I'm trying to understand the problem and learning as I go.
Every time one of the other switches tilts the machine, the second
from the right flasher on the row of back flashers, flashes. That
flasher should only flash when the left sling fires. You can hit the
upper left T target all day long and once every 30 or 40 hits the
thing tilts and that flasher flashes as if I've hit the left sling.

I guess my question is...or are: Is this caused by the left sling
transistor? All of those transistors from Q42to Q49? Or is there a bad
switch diode under there?

Stan

Look for either a diode shorted to a coil or switch frame or a bent switch
terminal that allows both ends of a diode to make contact, thus providing a
sneak path for the signals in the switch matrix. Don't just check switches
on the string that you think is the issue. Frequently a short on an
entirely different string can pull down the line that you think is having
trouble. If you have a switch matrix chart, look diagonally from the switch
that appears to be the problem and start checking the switches that are
diagonally opposite that switch.

If the problem only occurs when a coil fires, then check for a short between
the mechanicals of that coil and also disconnect and check the diode for
that coil for proper function. The back-EMF that the diode is responsible
for shorting out can cause random tilts and resets of the MPU.

Pistol Pete
Baltimore, Maryland


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