Re: TECH: System 9 Sorcerer Sound Help

Dave K wrote:
....First, I had to get rid of the '7' on the diag. display. I
replaced the game 6808 after reading some of the archived posts here. I
turned it on and saw a '0' now instead of the '7'!! It booted into the
machine audits (battery holder had been removed) woo hoo!

That is a major victory. I have repaired a few of these System 9s,
including one that showed the '7'. It is when the board is completely
dead, and often is not as simple as swapping a CPU chip.

There are no sounds or speech produced in the game, diagnostics or when SW2
is pressed. I have swapped the 6808's to make sure they are both good. The
amp U47 was replaced because it burned my finger (I'm still mad at that
thing ).

I just noticed that the amp is listed as U47 on the parts list, but is
U59 on the schematic. Where did you buy the amp? Was it from GPE?

With a logic probe I can see changing state on pins 2-8 of U13
during the sound test loop in the diags.

Those lines are how the main CPU (U17) lets the sound CPU (U11) know
which sound it wants. So the problem is entirely in the sound section.

I can see pulses on pins 26-33 of
U13 during the same test.

This shows that the sound CPU itself is running and is probably ok, but
that is not certain. Do the pulses swing completely to the rails? If
not, there may be bus contention on one of the lines, indicating a bad
ROM chip or other CPU peripheral.

I read somewhere that pin 19 of U13 should be
high when there is no sound, low during sounds, and pulsing during speech.

I can confirm that it pulses during speech. This is because the sound
CPU ships the speech data out to the D/A that is on the external speech
board.

My pin 19 is high no matter what is going on. I know this is a problem, but
I don't know what to do next. I feel like I'm so close.Any help would be
greatly appreciated.

Note that the D/A for sounds is U48 on the CPU board, but the D/A for
speech is U1 on the external speech board. The two streams are mixed
by U2 on the external speech board and then amplified by the amp on the
CPU board. Check the following:
- do the pins 5 through 12 on U48 toggle when you do a sound test?
- if yes, unplug external speech board and jumper W10. Any sound now?

Many ways this could go. Let me know what you find, and I will
continue to trace it with you.

BTW, this is my page dedicated to repairing System 9s:
http://www.edcheung.com/album/album05/pinball/cpu.htm
It has links to the other well known pages by Clay and Leon.

Edward Cheung CARGPB26
www.edcheung.com

.

Relevant Pages

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