Re: Squawk and Talk easy question
- From: bally@xxxxxxxxxxxxxxxxxxxxxx
- Date: Sat, 29 Mar 2008 20:14:41 -0700 (PDT)
On 30 Mar, 01:23, Tec-9 <pacmanfan1...@xxxxxxxxx> wrote:
Hey all,
I am working on a Mr. and Mrs. Pac-Man, and it has no sound or
voice at all. I am trying to troubleshoot the squawk and talk sound
board. My question is, what does the LED do after you get the fifth
flash? Does the LED go out, or does it go dim like it does on the main
MPU? I THINK I'm getting 4 flashes, but not the fifth. I am unfamilar
with this sound board, and I'm not sure about the intial flash, and
then I get some quick flashes.
Thanks-
Mark
From the fix site:
Squawk and Talk LED Flashes.
The S&T has a series of LED power-on flashes much like the MPU
does. Here's a description of the flashes.
First Flicker.
Fakers Guide: No flicker means a bad U5, flakey U15, leaky C1,
open R1, leaky CR1, or bad U17.
Techno Guide: On power up, U1 requires +5 volts to be applied
before the reset line is allowed to go high. If this condition is met,
the LED does a quick "flicker". At power-on, C1 slowly charges via R1.
The voltage across C1 is monitored by U15. When it reaches 1.7 volts
DC, U15 take the reset line high. Diode CR1 across R1 provides a quick
discharge path for C1 in the event the +5 momentarily disappears.
First Flash.
Fakers Guide: No first flash means a bad U6, U15 or U17.
Techno Guide: The U1 chip tests the U6 RAM. It attempts to write
then read back all 256 patterns in each of the 128 scratch pad RAM
memory locations. If U1 completes the 256 x 128 = 32,768 tests, the
LED is flashed.
Second Flash.
Fakers Guide: No second flash means PIA U7 is bad.
Techno Guide: The U1 chip now tests the first PIA U7. Each of
the two PIA chips U7 and U11 are interchangable. The test is the same
for both. If it determines the two PIAs are good, the U1 chip performs
some test. This includes testing each of the two full byte port
initialization registers, testing the two full byte I/O registers, and
testing the CA2 and CB2 ports. If all checks out, the LED is flashed.
Third Flash.
Fakers Guide: No third flash means PIA U11 is bad.
Techno Guide: The same test above is performed on PIA U11.
Fourth Flash.
Fakers Guide: No fourth flash means sound generator U12 is bad.
Techno Guide: The U1 chip performs a test on the sound generator
chip U12. The U12 chip is controlled by PIA U11. If the sound chip
passes the LED is flashed the fourth time. A bad PIA at U11 can also
cause no fourth flash! Or a bad connection between the three chips U1
(microproocessor), U7 (PIA), and U12 (sound generator).
Fifth Flash*.
Fakers Guide: NOTE: Some games, namely Fathom, will not have a
fifth flash! See the explaination below. No fifth flash means speech
chip U8 is bad. Also no fifth flash can be as simple as no -5 volts at
TP4. Note the -5 volts comes from the G.I. (General Illumination)
circuit. So if the GI fuse is blown, the sound/speech won't work
either (because the -5 volts will be missing on the sound board).
Thanks Cliffy!
Techno Guide: The speech generator U8 chip requires an
initialization sequence at power-on. Since the chip is a "slow"
device, there is an acknowledgement signal from the speech chip to the
U7 PIA. Every time a write to the speech chip is done, the speech chip
acknowledges. The U7 PIA attempts to send 9 bytes of initialization
data to the speech chip, one at a time, waiting for acknowledgement.
If it is sucessful, the speech chip is considered functional and the
LED is flashed the fifth time. A bad PIA at U7 can also cause no fifth
flash! Or a bad connection between the three chips U1
(microproocessor), U7 (PIA), and U8 (speech chip).
*No Fifth S&T Flash on Fathom (and some other games).
Fathom does not use the AY-8912 PSG (Programable Sound
Generator) chip at U12 (and has the EE jumpers installed on the S&T
board indicating it is not used). Because of this, only *four* flashes
of the S&T LED will be seen (after the initial power-on flicker). This
is normal and correct. Disassembly of the self-test ROM code for
Fathom reveals there are only four calls to the LED flash routine
instead of five.
.
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