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YM3812 + YM3014 issue
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Dajgoro:
Hi.

I am trying to build a synth device using original synth chips, and I am using the OPL2 chip in my project.
I am having problems with the output dac (YM3014), since I get no output.
The YM3812 seems to work properly, it is giving signals which look good on the scope, I can see the clock signals, and serial data being shifted out. The YM3014 datasheet suggests using a 072 opamp, but since I don't have that I used the LM324. The output seems to give a very faint voltage, because when I poke the oscilloscope probe at x10 I just see a discharge peak, and the opamp (in buffer mode) is giving out a fixed voltage.
I used this schematic as a reference:
http://cbm.ko2000.nu/schematics/cartridges/c64/sfx/sfx-sch.gif
Except that I didn't make that output amp part like that, but rather like the one shown in the YM3012 datasheet (simpler).

Is the chip defective, or did I do something wrong?
marshallh:
Maybe you have
1. Bad/fake LM324
2. Bad/fake YM3012 (clones do exist of the OPL family)
All I can think of barring wiring mistakes/forgetting to bypass supplies
Dajgoro:

--- Quote from: marshallh on August 22, 2013, 03:19:30 am ---1. Bad/fake LM324
--- End quote ---
I tryed replacing it with anoter one, no effect.

--- Quote from: marshallh on August 22, 2013, 03:19:30 am ---2. Bad/fake YM3014 (clones do exist of the OPL family)
--- End quote ---
Maybe, but I doubt that, since I got it from ebay recently.

--- Quote from: marshallh on August 22, 2013, 03:19:30 am ---All I can think of barring wiring mistakes/forgetting to bypass supplies
--- End quote ---
I added bypass caps, and I checked the wiring, didn't spot anything.
When I read the datasheet of both chips I got the impression that SH went to Load and SY went to Clock, but the schematics says otherwise. I tried both combinations, nothing changed.
Dajgoro:
I tried testing the DAC chip by glitching the serial input to some other random signal on the board, and I do get a random analog signal at the output, so the DAC is working, which means that the synth chip is always giving out the same value. So either the data bus has some issues, or the test data from the "Programming the AdLib/Sound Blaster FM Music Chips Version 2.0" has some issues (which I doubt).
I am driving the bus with a ATmega162@8MHz with double bus cycle.
I did try reading and writing to a ram chip, and that worked fine.

Edit: One problem fond, the addresses were messed up in code. :D

Edit2: Ok, I fixed that, now I can see the data alternating every few ms, but still no analog out.
And why on that schematic do the Load and Clock look inverted? Is it a schematic error, or is it supposed to be like that?
Dajgoro:
That schematic is wrong indeed.
I returned the wiring as I initially connected it.
I managed to get a signal out of the chip!  :D
But only after poling the reset switch a few times.
Also, I don't get the same tone every time.
Sometimes I get a higher frequency, sometime a lower, sometime just a steady tone.
Sounds to me like the bus is having issues, but I can't find any.
What could be the cause?
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