Whitestar - Monopoly - Way too loud!

[John Robertson]

Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't figure
out is the steps in the audio - are they simply data or is one of the
serial latches responsible?

My problem is the game sound (while pretty clear) is WAY too LOUD! Only
with one bar above zero is the sound OK, and that is loud for a small
arcade. Add any bars to the volume and distortion kicks in and the
volume goes up enough to be annoying/painful.

So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.

By the way, audio is controlled between 3800h and 3BFFh on the main MPU.
I worked that out with my Fluke 9010A today. Not exact memory locations,
but the audio enable was active for most of the calls to memory in that
range.

Thanks!

John :-#)#

[Todd Scott]

John,

I had the same problem with a game. I did this service update and it helped a lot. Todd Scott

https://sternpinball.com/wp-content/uploads/2018/10/sb133.pdf

[Kerry Imming]

Post by John Robertson
Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't figure
out is the steps in the audio - are they simply data or is one of the
serial latches responsible?
My problem is the game sound (while pretty clear) is WAY too LOUD! Only
with one bar above zero is the sound OK, and that is loud for a small
arcade. Add any bars to the volume and distortion kicks in and the
volume goes up enough to be annoying/painful.
So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.
By the way, audio is controlled between 3800h and 3BFFh on the main MPU.
I worked that out with my Fluke 9010A today. Not exact memory locations,
but the audio enable was active for most of the calls to memory in that
range.
Thanks!
John :-#)#

The audio data is written in parallel to U23 and U24 and then serially
shifted into U26, the digital-to-analog converter (DAC). I can't
imagine a problem in SD0-SD16 that could corrupt the audio data without
causing other problems on the CPU.

The service bulletin that Todd pointed out decreases the gain of the
main amplifier (TDA2030) and seems like a good thing to try.

U30 is a low-pass filter and probably set to a gain of 1 (no
amplification). If something went wrong with it or the R16, R17
resistors it could amplify the signal and probably cause distortion but
I would suspect that to only affect the left or right channel.

- Kerry

[John Robertson]

Post by Kerry Imming

Post by John Robertson
Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't
figure out is the steps in the audio - are they simply data or is one
of the serial latches responsible?
My problem is the game sound (while pretty clear) is WAY too LOUD!
Only with one bar above zero is the sound OK, and that is loud for a
small arcade. Add any bars to the volume and distortion kicks in and
the volume goes up enough to be annoying/painful.
So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.
By the way, audio is controlled between 3800h and 3BFFh on the main
MPU. I worked that out with my Fluke 9010A today. Not exact memory
locations, but the audio enable was active for most of the calls to
memory in that range.
Thanks!
John :-#)#

The audio data is written in parallel to U23 and U24 and then serially
shifted into U26, the digital-to-analog converter (DAC).  I can't
imagine a problem in SD0-SD16 that could corrupt the audio data without
causing other problems on the CPU.
The service bulletin that Todd pointed out decreases the gain of the
main amplifier (TDA2030) and seems like a good thing to try.
U30 is a low-pass filter and probably set to a gain of 1 (no
amplification).  If something went wrong with it or the R16, R17
resistors it could amplify the signal and probably cause distortion but
I would suspect that to only affect the left or right channel.
- Kerry

I had done the resistor change from the SB133 already, no improvement.

I agree it is hard to see how a data error would not cause serious
distortion too, but it is the volume that is simply way too high.

I'll try my logic comparator on U23, 24, and 26 just to be sure.

Weird!

Thanks,

John :-#)#

[John Robertson]

Post by Kerry Imming

Post by John Robertson
Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't
figure out is the steps in the audio - are they simply data or is one
of the serial latches responsible?
My problem is the game sound (while pretty clear) is WAY too LOUD!
Only with one bar above zero is the sound OK, and that is loud for a
small arcade. Add any bars to the volume and distortion kicks in and
the volume goes up enough to be annoying/painful.
So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.
By the way, audio is controlled between 3800h and 3BFFh on the main
MPU. I worked that out with my Fluke 9010A today. Not exact memory
locations, but the audio enable was active for most of the calls to
memory in that range.
Thanks!
John :-#)#

The audio data is written in parallel to U23 and U24 and then serially
shifted into U26, the digital-to-analog converter (DAC).  I can't
imagine a problem in SD0-SD16 that could corrupt the audio data without
causing other problems on the CPU.
The service bulletin that Todd pointed out decreases the gain of the
main amplifier (TDA2030) and seems like a good thing to try.
U30 is a low-pass filter and probably set to a gain of 1 (no
amplification).  If something went wrong with it or the R16, R17
resistors it could amplify the signal and probably cause distortion but
I would suspect that to only affect the left or right channel.
- Kerry

Hi Kerry,

Thanks for the clue! It turned out to be a bad DAC - the TDA1543 was
putting out too high a reference voltage. Normally this is -1.7VDC, but
here it was at +2.5! Now the reference voltage does not change depending
on the volume, but - of course - it does set the gain on the L&R Op Amps
U30A/B.

Volume is normal now, and regular adjustment range.

John :-#)#

[John Robertson]

Post by John Robertson

Post by Kerry Imming

Post by John Robertson
Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't
figure out is the steps in the audio - are they simply data or is one
of the serial latches responsible?
My problem is the game sound (while pretty clear) is WAY too LOUD!
Only with one bar above zero is the sound OK, and that is loud for a
small arcade. Add any bars to the volume and distortion kicks in and
the volume goes up enough to be annoying/painful.
So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.
By the way, audio is controlled between 3800h and 3BFFh on the main
MPU. I worked that out with my Fluke 9010A today. Not exact memory
locations, but the audio enable was active for most of the calls to
memory in that range.
Thanks!
John :-#)#

The audio data is written in parallel to U23 and U24 and then serially
shifted into U26, the digital-to-analog converter (DAC).  I can't
imagine a problem in SD0-SD16 that could corrupt the audio data without
causing other problems on the CPU.
The service bulletin that Todd pointed out decreases the gain of the
main amplifier (TDA2030) and seems like a good thing to try.
U30 is a low-pass filter and probably set to a gain of 1 (no
amplification).  If something went wrong with it or the R16, R17
resistors it could amplify the signal and probably cause distortion but
I would suspect that to only affect the left or right channel.
- Kerry

Hi Kerry,
Thanks for the clue! It turned out to be a bad DAC - the TDA1543 was
putting out too high a reference voltage. Normally this is -1.7VDC, but
here it was at +2.5! Now the reference voltage does not change depending
on the volume, but - of course - it does set the gain on the L&R Op Amps
U30A/B.
Volume is normal now, and regular adjustment range.
John :-#)#

Forgot to mention the problem was solved in my previous post...

John :-#)#

[Kerry Imming]

Post by John Robertson

Post by Kerry Imming

Post by John Robertson
Anyone here looked into how WhiteStar board sets the audio volume? As
near as I can figure out it is data buried in SD0 to SD7 data between
the audio 6809E, the Basement 2K chip, and the DAC. Where I can't
figure out is the steps in the audio - are they simply data or is one
of the serial latches responsible?
My problem is the game sound (while pretty clear) is WAY too LOUD!
Only with one bar above zero is the sound OK, and that is loud for a
small arcade. Add any bars to the volume and distortion kicks in and
the volume goes up enough to be annoying/painful.
So, I'm trying to figure out how audio volume is done digitally...I do
have a request in to Stern tech, but not sure if they know these older
(for them) games that well.
By the way, audio is controlled between 3800h and 3BFFh on the main
MPU. I worked that out with my Fluke 9010A today. Not exact memory
locations, but the audio enable was active for most of the calls to
memory in that range.
Thanks!
John :-#)#

The audio data is written in parallel to U23 and U24 and then serially
shifted into U26, the digital-to-analog converter (DAC).  I can't
imagine a problem in SD0-SD16 that could corrupt the audio data without
causing other problems on the CPU.
The service bulletin that Todd pointed out decreases the gain of the
main amplifier (TDA2030) and seems like a good thing to try.
U30 is a low-pass filter and probably set to a gain of 1 (no
amplification).  If something went wrong with it or the R16, R17
resistors it could amplify the signal and probably cause distortion but
I would suspect that to only affect the left or right channel.
- Kerry

Hi Kerry,
Thanks for the clue! It turned out to be a bad DAC - the TDA1543 was
putting out too high a reference voltage. Normally this is -1.7VDC, but
here it was at +2.5! Now the reference voltage does not change depending
on the volume, but - of course - it does set the gain on the L&R Op Amps
U30A/B.
Volume is normal now, and regular adjustment range.
John :-#)#

Wow... nice find John. I don't know why I find it so strange that the
Vref failed but I'm glad you found it.

- Kerry