Willzyx x0xb0x Completed, no sound (solved)

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Vasiliovich
 
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Willzyx x0xb0x Completed, no sound (solved)

Post by Vasiliovich »

It is as the title says, I finished everything but I'm not getting any sound. Perused the forums, and I decided it would be better to just give my specific situation as opposed to trying to match with another's.

A little background:
I have a multimeter and an older, analog oscilloscope for debugging. I've been using two AA batteries to get the 3 volts, and I have an adjustable power supply that reads fine on the multimeter when I'm trying to get 2 volts or 3 volts, but when I connect it to the board it's a no go, none of the readings on the oscilloscope match what the batteries give. That's neither here-nor-there, but it's worth mentioning. I was also able to successfully test as I was building, but at this point I simply don't know where to start. Any help would be appreciated.



As a side note, which way is IC14 supposed to go? I couldn't find anything specific in my build manual, and the images on the x0x site aren't particularly helpful for this piece.
Last edited by Vasiliovich on Sat May 04, 2013 3:31 pm, edited 1 time in total.

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antto
 
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Re: Willzyx x0xb0x Completed, no sound

Post by antto »

from this picture:
Image
i'd say the chopped-off side should be towards the end of the PCB

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antto
 
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Re: Willzyx x0xb0x Completed, no sound

Post by antto »

if the sequencer works properly, then you can start from the VCO onwards
check if you got sawtooth/square at the waveform switch

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

The white keys' leds light up when I hit each key in keyboard mode, but I can't be certain that the entirety of the sequencer is actually working.

As for the waveforms, they have both been confirmed.

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

If you've already installed IC9 you can play (in keyboard mode) the low and high C and then measure the voltage on pin 7 of IC11.

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

Low C: 5.09
High C: 5.09

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

Please check at pin 5 of IC11 as well. If the results are similar the digital side does not work.

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

Retested pin 7 this morning and got:
Low C: 6.44
High C: 6.45

Pin 5:
Low C: .83
High C: .83

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

So that doesn't work as well.

So let's see if anything works at all on the digital side of things.

If the xoxbox is in "Patt Sync Out" mode: Does the Tempo LED blink? Does it react to the tempo encoder? Does the Bank LED light up according to the position of the bank switch?

You mentioned that in Keyboard mode LEDs light up for the white keys. Does that mean that they don't light up for the black keys?

And finally: Please measure at R146 what happens when the xoxbox is in keyboard mode and you press a note button (use the R146 leg that's closer to the processor - the one that attaches directly to the long PCB trace).

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

Hold up, scrap everything (except for the fact it makes no sound). Turns out I was in the wrong mode (that's what I get for assuming a knob's direction without its cover).

Also, I had a realization; when you say low and high C, does that mean I should or should not change the range of the keyboard? In that, it truly is the lowest and highest Cs, or just the Cs of the default octave?

At any rate, here are the measurements of all of them:

"Default Keyboard Range C [Presumably C3 to C4]"
Pin 7 for IC11:
Low C: 2.0
High C: 3.0

Pin 5:
Low C: 1.82
High C: 2.72

"True Low C and High C"
Pin 7:
Low C: 1.0
High C: 5.0

Pin 5:
Low C: .91
High C: 4.53

Patt sync out mode has a blinking tempo light, and it does react to the encoder. The bank lights also match the position of their knob. The black keys are fine, I think I was in Patt Edit mode before.

R146: 4.95 when any key is pressed.

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

Well, that all looks very good now. Seems like the digital part is working quite well.

So let's trace the signal. Please measure with the oscilloscope at the following points:

- middle pin of waveform switch (try both waveforms)
- "-" side of C17 (waveform will be much weaker than before)
- "-" side of C14
- pin 1 of IC15B
- pin 8 of IC15B while playing a note

The voltage of the waveform will vary widely (from about 5V peak-to-peak to about 100mV) depending on the point you're checking. You'll also have significant amounts of DC offset at various points so it is a good idea to check in AC coupled mode.

If you don't get any signal at the waveform switch you don't need to continue further (because then the oscillator isn't working).

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

Oscillator seems fine, both waveforms were there, though the square wave wasn't super square.

C17 has a very weak saw tooth waveform.
C14 doesn't seem to have much of anything.
Same with pins 1 and 8 of IC15B, nothing.

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

Vasiliovich wrote:Oscillator seems fine, both waveforms were there, though the square wave wasn't super square.
That's perfectly normal
C17 has a very weak saw tooth waveform.
If "very weak" means about 100mV then it's ok as well.
C14 doesn't seem to have much of anything.
Which means the signal isn't making it through the filter (I'm assuming you have set Cutoff to max). Before we start measuring within the filter: What's the code printed on Q22 (the 2SC2291 dual transistor)?

Vasiliovich
 
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Re: Willzyx x0xb0x Completed, no sound

Post by Vasiliovich »

"C2291
440" is printed on Q22

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mmm
 
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Re: Willzyx x0xb0x Completed, no sound

Post by mmm »

Thanks; at least so far this code hasn't been known for fakes so chances are Q22 is the "real deal".

So we're going to check the filter ladder.

Please measure with the multimeter the voltages at

C18
C19
C24
C26

and the two bases of Q12.

You may also want to check with the oscilloscope if there's any signal along the ladder C18, C19, C24, C26 (but it will be very weak and travel on top of a large DC offset).

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