My Dig Dug lets the smoke out of my 4017 chip

[pbrommer1]

... or why doesn't my Dig Dig v2 work?

Hello everyone-
I realize this is my first post, but I've lurked on and off since purchasing a couple of madbean boards and getting them (not)working. I have built many successful (and unsuccessful) pedals over the years, but this one is stumping me.

Here are some pieces of information that might help:

Source voltage: steady 9.45v from OneSpot

IC1 OP271 (only dual opamp I have at home) -- these don't look bad to me
1 - 8.12
2 - 1.297
3 - 2.567
4 - 0
5 - 1.259
6 - 0.001
7 - 0.776
8 - 9.45

IC2 HCF4017BE -- these look wrong, and even the chip might be wrong. I checked the data sheets - they match - but I don't know for sure (the only difference I saw was clock enable on the HCF4017 and clock inhibit on the cd4017be)

Preface -- When I first powered it up, I remember hearing a faint hiss. I still ran the voltages with the 'fried' chip, which produces a very distorted, farty sound when listened through an amp. These were the voltages:
1 - 0.169
2 - 0.166
3 - 6.23
4 - 0.273
5 - 0.192
6 - 0.184
7 - 0.175
8 - 0.001
9 - 0.021
10 - 0.014
11 - 0.017
12 - 9.46 (this looks wrong)
13 - 0.013
14 - 9.47 (this looks wrong also)
15 - 0.076
16 - 9.45

Today, I replaced the HCF4017BE with the same chip. Listened closely as I powered it up and heard "phhhssssshhhhh" and felt that the 4017 had fried. Argh.....

Just for more information:
IC3 HCF4093BE
1 - 1.67
2 - 1.69
3 - 8.07
4 - 1.64
5 - 5.06
6 - 8.09
7 - 0
8 - fluctuates
9 - fluctuates
10 - fluctuates
11 - 9.46 (might fluctuate also)
12 - 4.74
13 - 4.74
14. - 9.46

Before I replaced the second 4017 I had, the LEDs would light up completely and would be controlled by the pots. The filter pot had control over some depth of sound (I could hear a change in the farty sound - more bass to less bass). Speed pot didn't work, but I later found that there was a bad connection from the board to the speed pot. I also took out the Vactrol and replaced it with an LED. Also, I removed the random (DPDT) switch from the circuit. The DPDT would cause the LEDs to change in intensity. The 3PDT would not cause any bypass -- the LEDs would always stay on.

With the LED from the potentiometer board, it only causes all of the LEDs to light up in one direction - the other direction causes no change. The correct direction of the above LED causes the LED where the vactrol is to light up also.

I'm thinking there is obviously an issue in the sequence portion, but I'm not sure where to start. I believe that the solder joints are okay - I did reflow them to double check. I wonder if there is a pinout issue with the BS170 and transistors (I had to use MPSA18 - what I had on hand). I have checked it against the schematic and it should not be an issue. Maybe there is a bad diode. Any ideas? I have the madbean correct parts on order, but I want to make sure I have voltages correct so I don't smoke another CD4017. Thank you very much in advance.

Patrick

P.S. I still need to troubleshoot a couple more pedals -- they're all acting weird lately.......

[stecykmi]

dig dug is a very tricky build, mine sat half-finished for a year.

Anyway, check for solder bridges. check Q3 and Q4 as well as the 4093 for correct pin placement. It looks like your clock isn't working based on the voltage at pin 14 on the 4017 so that's a key thing to get correct.

If you etched the board yourself, carefully check for copper connections where there shouldn't be. this was a major bug in my build.

[pbrommer1]

Thanks for the ideas stecykmi.

I forgot these in the rush to post the help before I fell asleep.

Q3 (bs170) -- This looks a bit weird to me.
D- 9.45v
G- 0.5v
S- 5.1v

Q4 (mpsa18)
C- 9.45v
B- 2-5v (I think it was fluctuating a bit)
E- 0 (at ground)

Q2 (bs170) -- these look wrong
D-  0.03v
G- 9.45v
S- 0.05v

Q1 (mpsa18 for the wah portion) looks good to me.

Maybe these numbers will help just a bit. Thanks everyone.

Patrick

[pbrommer1]

Happy new CD4017B day! 

No changes to report. Voltages seem to be the same. EXCEPT:
1. The LED that replaced the Vactrol is not lighting up.
2. No voltage on pin 6 on IC1 (TL072 -- I changed it out.).
3.  I didn't feel the CD4017B heat up nor did I hear hissing, so that may be a good sign.

IC2 CD4017B
1- 1.501
2- 1.503
3- 1.46
4- 1.442
5- 0.067
6- 0.002
7- 1.512
8- 0.00
9- 0.001
10- 1.483
11- 0.002
12- 7.80
13- 0.00
14- 7.80
15- 3.65-3.90
16- 9.46

Probing around for voltages, I saw so weird things happening at the positive side of c14. Big fluctuations, even along the trace up to R28 and R27. Fluctuations for 2.5-3.6V. Pins 12 and 13 of IC3 (4093) is acting a bit weird also -- doing the same fluctuation. Any ideas on where to look? Transistors? BS170? New 4093?

Patrick

[pbrommer1]

Bumping this up to the top with a couple updates. And a plea for a direction.

So far, I've made a few troubleshooting improvements.

1. I reversed all of the potentiometer board LEDs -- they were backward. Pot control is fine, and the 4/6/8 switch shuts a few LEDs (though I don't think it's the right ones - the 6 setting shuts off 8 and 8 but leaves 7 on....).

2. Bypass is working through the 3PDT. Big improvement there.

3. Sound is still farty when listened to through an amplifier.

4. Vactrol replaced with an LED. LED lights up with one setting of the DPDT, but it is shut off on the other setting. Hmmmm.... thought it should be on all the time.

5. Voltages haven't changed much. I'm now ironed down to looking at the CD4017 area -- something isn't right, I don't think.

If you have any ideas on where to go, please let me know. I'm still searching for an answer. Thanks in advance.

Patrick

[stecykmi]

the 4017 works with a clock and a reset signal. the reset signal is set by the 4/6/8 switch by selecting the point at which step the counter resets itself. in other word, the logical "high" voltage reset is generated by the 4017 itself. on the schematic, point PB5 (which is actually the 5th sequence position) is used to generated the "4" step sequence (notice the pots are not in order!).

assuming the sequencer is set to 4 steps, as soon as PB5 goes high, pin 15 on the 4017 goes high (the reset pin), and the sequencer immediately resets itself.

with this in mind, check your wiring again, especially for ORDER of the pots (i messed this up myself). you may be able to try probing pin15 with an audio probe to try listening for the reset signal, but careful since it may be very loud. i did this project with the help of an oscilloscope, which was very helpful.

try testing the analog filter section by replacing the LDR with a normal resistor (or pot). maybe try a 1MEG pot with a 1k resistor in series, just to prevent the resistance from being 0 and therefore grounded. see if it sounds like what you'd expect...

[pbrommer1]

I probably should have stated that I still don't get any blinking in sequence or random -- they all stay on solid.

I'm thinking there is trouble in the TL072 area, as the voltages look really weird. 7.6V on pin 1 does not seem right. I'm wondering if I have bad diodes or bad 10k resistors. They all are the correct values, but something is off.

I'll double check on wiring (which I have) and check Q2. I pulled Q2. The LED that replaces the LDR is just an LED that is solid on with the DPDT at one setting and then off with the DPDT in the other position.


I will look at what you stated, so hopefully I'll find an answer soon.

Patrick

[stecykmi]

this project is really hard to debug without an oscilloscope. pin 1 of the tl072 probably produces a sawtooth or triangle wave, although its too slow to be heard (it's at the speed of the sequencer - below the audio range). i don't fully understand how the 4093 section works, but pin 3 produces a square wave of the same frequency as the tl072.

with a scope, it would be two simple probes to see if it's working correctly.

[pbrommer1]

Well, I've made some progress. I have now got the Dig Dug running somewhat. The lights are now flashing in an almost random-ish pattern. It doesn't necessarily cycle straight through, but it's not always random.

Like the title says, it's like Speedy Gonzalez did one too many "speeding-up drugs" for waaaaay too many nights. The LEDs run fast - really fast! Hyperactive fast. The LED that replaces the vactrol is flashing in time with the LEDs, but at an extremely high rate of speed. I'm thinking there is some trouble with the voltage making things run really fast. Speed pot has no effect on the flashing.

It looks to me (using an online simulator of the circuit) that the 2n3904 is way too hot voltage-wise (collector and emitter are at almost 9.4V from a 9.45V source), along with pins 1 and 6 (almost 6V). I'm wondering if I have a bad resistor/wrong resistor somewhere, perhaps a bad capacitor or diode. Also, LED on pot 7/pot 2 (depends on how you are looking at the board - second to last one on the opposite side from the SPDT switch) does not flash, it holds steady.

Any ideas? I can't debug with an oscilloscope - don't have one. I'm getting closer to having it solved, but still having trouble. Thanks a million for all of the ideas.

Patrick

[stecykmi]

C9 sets the speed of the oscillator, so check there for problems (i would pull the cap and check it or replace it).

[pbrommer1]

Pulled C9, which when empty, let the sequencer run correctly (although really really fast like I stated in the last post). I replaced C9 with a new 3u3F electrolytic and it completely stopped the sequencer. There no longer is any sequencing at all. None. I didn't mention that in the last post.

One interesting thing is that if I tap around with a meter probe I can get the LEDs to jump one step (although not perfect). If I short the Gate and Source of Q2 with the random switch on, I can get the sequencer to hop around a bit. Not perfectly, but it changes the LED that lights up.

Thirdly, when I plug in the OneSpot, two LEDs come on strong. Each time, it's a different pair. Sometimes, 4 turn on, but then back down to two. One will control both LED intensities, and the other will turn down to almost zero (just a bit of light comes through).

Voltages are weird.

UC1 -- All looks good except pin 1 which is at 1.36 and pin 3 which is at 2.5-3.1V
UC2 -- Still doesn't look quite right in places. Some are better than others
UC3 -- Lots of 9.45V (that's the voltage from the wall), especially on pin 1, 2, 4, 5, and 14 (UC3 power). Weird......

Q4 has at least 9.2 volts on each leg. That can't be right.