DigDug2 is digging too soon.

[neandrewthal]

Everything seems to work fine for the digital controls. The tremolo works, wah doesn't (but I'm not going to worry about that until later) The only problem (for now) is that the 8 pattern LEDs go completely dark when the corresponding pots are turned slightly less than half of the way clockwise. This also means that only about 25% of the pot's rotation is useful for setting tremolo volumes and it's very hard to do without just making each step full volume or silent.

I've got 5.02v on pin 16 of IC4. 3.86v coming out of it to pin 1 on the pots and coming out of pin 2 of the pots when they are fully CCW.  1.86v across the 8 LEDs when they are fully lit. At the point where the pots are turned just until the LED goes fully dark I have 3.15v on the wiper of the corresponding pot.   I have 1.8v +/- .05v across the global pattern LED and the vactrol LEDs (I have normal yellow LEDs instead of vactrols) when they are lit too. Those 3 LEDs also seem to have the appropriate resistance from their cathodes to ground.

I'm guessing my problem has something to do with only 3.86v coming out of the 4017 instead of 4.77 like it says in the build doc. I just swapped for a different one and this time I have 3.89v.

Anyone have any idea what could be going wrong?

[madbean]

What you are describing sounds pretty much how it operates. As it says in the build doc, most of the LED control is in the first half of the turn with it going very dim and completely off as you go further. The range over across the pots for the LED brightness is pretty small and that's the nature of the circuit - fine tuning.  However, a lower voltage on IC4 could limit the LED brightness further like you are describing so it could make it worse.

What kind of vatrol are you using? Did you use a VTL or Macron or roll your own? Wondering the the internal LED of your vactrol could be in play here.

[neandrewthal]

You are right, the doc says "Most of the brightness manipulation will occur in the first ½ of the turn. After that the LED will go very dim and then off." However, on mine ALL the brightness manipulation occurs in the first half of the turn. The LEDs shut off completely by about 11:30. I guess the size of the discrepancy depends on exactly what is meant by most. Maybe it`s not really that far off.

At first I had RYO vactrols with white LEDs but I unrolled them and stuck normal yellow LEDs in the sockets. It didn`t really make a difference. Now I just tried green and blue, same deal except the green and blue LEDs are very dim.

Next I decided to try running the 4017 on 9v instead. Now the LEDs dont even start to dim until about 12 oclock and they dont go fully dark at about 4 oclock, so it seems like I`ve just shifted my problem to a different range, but hold up. Let`s stick the yellow LEDs back in see how it sounds with the tremolo.

Wow! Now were in business. Even though the LEDs dont get noticeably dimmer until 12 oclock they make a noticeable difference in the volume right away and I have all the way til 4 oclock til it goes silent. Now I have tons of control which is essential for making complex tremolo patterns that arent just on and off.

I just had a blast playing with this thing but now its time to get back to work. I havent checked out the wah circuit at all yet so Ill give it a go and report back with my success or failure.

[neandrewthal]

So I went through the whole filter section point by point before I did what I should have done first: replace the 5088. Then I could just barely get some wah modulation going on with the frequency and resonance cranked. Switched to a white LED for the opto and I got a better frequency range (before the filter wasnt opening up enough) When I turn down the resonance it seems to decrease below the ideal level again. It also pops, no doubt due to the extremely bright white LED.

I think my problem now is just the stupid LDR I`m using without the proper light/dark resistance, but Im sick of this for now so Ill look into it later. 

[neandrewthal]

Yeah, Vact1 is supposed to be VTL5C9 with a light resistance of like 100ohm (I cant find it actually listed, just a chart with an exponential scale) or sub 5C3 with a light resistance of 1K. My photocell has a minimum resistance of 10k!

Oh well, I`ll fix that later. Now moving on to mods. Time for sync input, clock output, CV output and possibly slew/lag/portamento/glissando/whatever if I can figure it out.

[Hangingmonkey]

Let me know if you figure out the wah issue, I have the same problem as mine trems but doesn't wah


Sent from my iPad using Tapatalk

[neandrewthal]

Im 90% sure I just need a better LDR cause Ive got mine wahing, just not high enough, even with the 4017 running on 9v.

What type of vactrol or LED/LDR combo did you use for the wah? Does it pass signal in the wah mode? If so, what does it sound like?

[Hangingmonkey]

I used the vactrols as specified in the BOM. It passes signal in wah mode but doesn't really sound filtered. Also when I turn the filter and Rez trimmers I can't hear a difference.
I tried your earlier suggestion of changing the 5088, I didn't have one to hand so I tried a 2n3904 but no difference.
I think my 4017 might be dodgy. All the voltages are as in the build doc but in bypass mode, all the pins have varying voltage 0-up to 2.5 depending on the pin, with the exception of pins 8, 9, 11, 13, 15, 17 which are zero. According to the build doc most of the pins on the 4017 should be zero in bypass mode.


Sent from my iPad using Tapatalk