Star Wars audio problem constant popping, clicking whatever

Matt Mac Donagh

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Jan 8, 2006, 9:09:42 PM1/8/06

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Heres another one I'm bound and determined to fix. I have two Star Wars
audio boards that boot up, make that three pop (or click) sound that SW
makes upon power up and then proceeds to pop twice every second or so.
Looking at the schematics I have been able to determine that the speech chip
(TMS-5220) is being turned off and on through a few transistors which are
driven by PA5 (Pin13 of the 6532 PIA). I have not been able to determine why
the PIA is acting like it is. All socketed IC's are good, all of my voltages
are good and clean. The board will generate game play audio for a split
second from time to time. If I go into the RAM\ROM test I get 16 good tones
indicating that all RAM and ROM check good. I've also tried this sound board
with another working CPU and AVG board, same results.

I've run across this very problem 7 or 8 times in the last 5 years. I'm
going to figure this one out and post the fix here. A google search comes up
with others that have had this problem but no definitive fixes. This cant be
all that complicated.

--
Matt

M and M Electronics

Matt Mac Donagh

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Jan 8, 2006, 9:47:17 PM1/8/06

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Did some more digging. Looks like two people have had this problem and fixed
it by changing the LS161 in the Speech clock circuit. I will follow up
later...

"Matt Mac Donagh" <game...@gmail.com> wrote in message
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RocketAero

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Jan 9, 2006, 12:29:45 AM1/9/06

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Thanks Matt. This is good info. I have the same problem with my ESB boards
... sounds present with clicking and no speech.

Tony

"Matt Mac Donagh" <game...@gmail.com> wrote in message

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Matt Mac Donagh

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Jan 9, 2006, 1:40:37 AM1/9/06

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I'm really hoping that this will fix these two boards. I've got three more
sets at the shop I used to work at in Cali and will be packing them up next
time I'm out there.

We'll find out tomorrow.

Posted for future Googler's!

Matt

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simon hanlon

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Jan 9, 2006, 3:06:10 AM1/9/06

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I have a few with the same problem Matt...let me know if you find the
problem

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Rob Carroll

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Jan 9, 2006, 9:26:46 AM1/9/06

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A dislodged/bad CPU on the sound board can also cause this.

Matt Mac Donagh

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Jan 9, 2006, 11:12:26 AM1/9/06

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CPUs tested good. The sockets are OK too.

"Rob Carroll" <robert.c...@verizon.net> wrote in message
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Chris

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Jan 9, 2006, 2:02:24 PM1/9/06

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Check the voltages on the outputs of the 74C04 hex inverter at 2F (pins
12 and 2) or where it goes into the TMS5220 (pin 6). The inverter takes
the TTL-level output of the clock circuit and drives the voltages from
-5V to 5V for the speech chip. Several of the inverters are tied
together to drive the output. On my board one of the inverters seemed
to be shorted - I would get a nice square output clock signal on the
scope but the voltages would only range from 5V to 2V instead of all
the way down to -5V. 2V isn't really low enough to trigger a "low" in
the signal so the speech chip hung and kept getting reset.

If this is actually the problem and you need to replace the chip, note
that this is a CMOS 74C04 and not a standard TTL 74LS04 (because it is
running 10V instead of the normal 5V).

-Chris