TECH: TZ Sound Problems - Now I'm officially stumped

[Eric]

Archived from groups: rec.games.pinball (More info?)

I am still having the problem with my TZ sound where the music comes through
fine, but any spoken word sounds are very, very low in volume and static
filled. Below is a list of things I have checked and done:

1. Checked all speakers to make sure none were blown.
2. Replaced the 3.5" speaker just to be sure.
3. Verified connectors were in right location and reseated IC's and ribbon
cables.
4. Replaced R22-25 with correct resistors (R22 and R25 = 120K, R23 and R24
= 56K).
5. I am running 9.4H and L2 ROMs.
6. Looked over the sound board to try and find any obvious component
failures.

At this point, I'm stumped. I am taking my board to test in another TZ but
I have a hunch the issue is in the board.

I was looking in the schematics and found what looks like four outputs: CH1,
CH2, CVSD, and DAC. Does anyone know which one of these outputs the spoken
voice would be on? I am going to start going through them and I don't want
to have to go through all 4 if I don't have to. Any ideas on components
that might have failed? I am guessing that the U8 Op-amp is working ok
since the music portion of the sound is working great.

Any advice or tips are welcome and appreciated.

thanks,
Eric

On a funny side note, I got a few odd looks at work when I said "I can't
hear voices from the Twilight Zone".

 

[martin]

Archived from groups: rec.games.pinball (More info?)

I was just looking at this; the schematic is open on my office floor,
but that's about 2,000 miles away right now.

CH1 and CH2 are the outputs from the MIDI synthesizer. So the spoken
words will be on either the CVSD or the DAC (my bet, CVSD).

I would be inclined to clip a 10K resistor in parallel with R22 - R25
in turn and see what happens to the sound. It should make the channel
louder (hint: start soft). Go for the CVSD first. See if that brings
your sound into acceptable ranges, or at least gives you a shot!

Try that, and post back - it should be a quick test. If nothing else,
I'll be back to my schematics in a couple of days. It is possible that
you have a problem in the speech chain itself; getting the sound to
higher volumes will expose that.