Where did 1, 4 and 6 go?​ CD4029 counter question

[BlackbeardsBrother]

I'm a novice and should point out first that I don't really expect an exact answer to this question- just anything that might point me in the right direction. I've designed a drum machine 5V module and have a very unexpected problem now that I've put it all together. To select the desired drum pattern, I have a rotary encoder connected to a CD4029 counter almost identical to this tutorial: https://www.youtube.com/watch?v=JXGFWW4CDPw (except that I don't use the additional 300pF capacitor on the clock input as I didn't have any trouble without it to now). I'm using the Q1, Q2, Q3 outputs on that counter to drive a single 7 segment display via a CD4511 "BCD to 7 segment" chip. The actual drum patterns are channel inputs to a CD4052 (8 channel multiplexer) with binary inputs S0, S1, S2. Thus, the display should go only from 0 to 7.

My exact pinout on the CD4029 is:

• pre-enable: connected to Q4 (to reset display to 0 on count 8)
• jam inputs P1, P2, P3, P4: all connected to ground
• carry-in, B/D (pin 9): ground
• Q1, Q2, Q3: connected to Q1, Q2, Q3 on the CD4511 and S0, S1, S2 on the CD4052 multiplexer and also to 3 LEDs for debugging so I can see the count in binary without the display

Pinout on the CD4511:

• Q4: connected to ground
• pins 3 & 4 (lamp tests): connected high (5V) to deactivate
• pin 5 (latch enable): ground

Ok, so here's the problem: as long as I don't connect any of the pinouts (F, G, A, B, C, D, E) from the CD4511 to the 7 segment display, I can turn the rotary encoder and see via the 3 LEDs that the counter is working properly counting from 0 to 7 (and "in reverse" it stops at 0). However, as soon as I connect a single pinout to the 7-segment display, it actually starts counting a different sequence: 0, 2, 3, 5, 7. Where did 1, 4 and 6 go?

[Mick Bailey]

Do you have series resistors in outputs of the CD4511? What happens if you connect one of the outputs to an LED instead of the display - does it still change the count pattern?

[BlackbeardsBrother]

Mick Bailey Thank you. I currently don't have any series resistors on the outputs of the CD4511 (other than, of course, those connected for the display, i.e. one resistor for each of the 7 segments). After I wrote my first post I figured there must be some shoddy soldering somewhere and resoldered some joints that looked dodgy. I will test connecting an output to an LED as soon as I get everything hooked back up (unless it immediately works as is). Probably has nothing to to with it, but I should point out that I observed something similar happens if the "breakout board" used to connect the rotary switch to the CD4511 clk input (see above tutorial link) isn't getting proper 5V power- then when you turn the rotary switch it also skips numbers.

[Mick Bailey]

The resistors I refer to are the ones connected to the display, so that's fine. Skipping numbers can also be down to switch bounce, though this is usually unpredictable in that the skipping is random. It's odd that connecting the display causes the problem - hence testing the outputs with an LED instead of the display to try to isolate where the fault may lie.