Re: Firepower Sound Help - Part 2

"Speeders" wrote:
Here are the symptoms this machine currently has - I realize there may
be layers of issues here - any help will be appreciated.

1. The credit knocker doesn't knock.
2. There is no background audio in spite of it being programmed "on".

Both of these could be related. They are both controlled (switched to
ground) by driver transistors on the driver board. I'd first check to see if
either of these driver transistors are actually firing when they're supposed
to. Often you can cycle them in solenoid test mode. Or watch the one for
"sound" during game play. Use an oscilloscope or logic probe to look for
valid signals going to the pre-driver and driver transistors from the 740x
chips that control them (and/or signals from PIA to 740x further upstream)
and maybe even tie a powered test lamp to the pin on the connector on the
board for each "coil" circuit to see if it blinks when the transistor is
supposed to be firing.

Obviously, if transistors are firing and signals are good, then you've got a
problem OFF the driver board- either in the connetions between driver and
sound board, or on the sound board itself.

Some approaches and steps like this will help you determine what's good and
what's not on the board, and help you narrow down the cause/source of the
problem.

Have you removed all circuit boards in the backbox and reflowed solder on
the backs of the connector pins? This is a must in any of these old
26-year-old games- and the first thing we do on any of these games that come
in our shop for repairs or overhauls. Get all the cracked solder joints
cleaned up to ensure good connections and that will increase the reliability
of the game and often eliminate a lot of intermittent problems.

3. The machine comes up in the "04" bookkeeping/feature setting mode
after powerdown. I have to hit advance then cycle power to clear the
game for play.

Battery issue? Do you have any batteries in the game or are they good? Is
the battery holder good? You must be getting power from the 3 "AA"
batteries on the board to pin 22 of IC19 CMOS RAM chip, when game is turned
off- it must be over 3.6vdc. This keeps memory when power is off.

Most common causes of failure here are corroded battery holder, or bad CMOS
RAM chip.

4. Many, not all, of the sounds are miscued. For example, the 1-6
targets seem to play the "tilt" warning. The game starts out by saying
"Fire Power Mission Accomplished" - there is no audio at Game Over.

This is a classic symptom of cracked solder joints on the back sides of the
connector pins on the circuit boards in the backbox. Specifically, some on
the left lower side of the driver board, and the ones along the top of the
sound board. Basically you have intermittent or open connections on some of
the lines here, so signals don't get through (reliably) and the sound board
then misinterprets the signal, and plays a different sound or speech
combination.

There's other causes, too, but very unlikely- connections is usually the
cause of this in the Williams games.

At this point, and I don't know why, I am suspicious of the soleniod
driver board. Does that seem reasonable? The sound board plays the
diagnostic set the right way - although I found blown and replaced the
leftmost fuse on the sound board - upper right.

Diagnostic button on the sound board will always play all the sound and
speech samples- even with the board disocnnected from the driver board
(9-pin connector at far left top of sound board)- as long as everything on
the sound/speech boards is good.

So you'd have to look "off board" for the cause- either at the connector
pins on sound board (cracked solder joints as mentioned above) or connector
pins on the driver board- lower left corner connector on driver. I'd check
those first- they are usually the cause of these problems 95% of the time.

Check for loose wires in the IDC connector housings that plug on to the
board, too. Wires have been known to wiggle a bit loose (intermittent) in
these over 26+ years. They basically just "press" in to the connector
housing- not crimped or soldered like earlier games (unless you have a real
early Firepower). But check for this as well as cracked solder joints on the
back of the boards' pins.


Ray J.
--
Action Pinball & Amusement, LLC
Salt Lake City, Utah USA
Web: www.actionpinball.com

We're serious about pinball. Anything else is just for fun!


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