Question on Dig Dug schematic about 4/8/6 switch

[maysink]

Okay. My schematic reading skills peak around following the line from left to right so I'm wondering if anyone can tell me if the following is correct or wishful thinking...

The 4/8/6 switch is an spdt center off switch. In the center (off) position the switch is doing nothing allowing all 8 stages to occur. When switched to the '4' position, the switch grounds/cancels stage 5 (and ostensibly 6, 7, & 8 ) leaving you with 4 stages. When switched to the '6' position, stage 7 (& 8 ) is grounded/cancelled leaving you with 6 stages.

That makes sense to me but am I making it up?

[madbean]

You are more or less correct. The switch doesn't ground anything, but rather when the two outside portions connect with the center pin in their respective positions, the internal clock of the 4017 is reset. The clock will cycle through on its own through however many outputs are used (there are two unused ones in the Dig Dug) until or unless it is interrupted and reset. D4 blocks signal flow through the circuit and sends it directly to pin 15 which is the reset pin. That makes the cycle start over. So, depending on what output you do that from, that's the number of steps in your sequence (you see from the schematic that the number of steps is actually n-1 steps - the switch connects P5B which means the cycle is 4 steps).

[maysink]

Thanks for the official word, MB. If I keep inventing my own science I might have to write for star trek!

Like an a-hole I inserted the 4017 chip backwards in the socket. When I pulled my head out and installed the chip correctly everything worked BUT pot/led #7 and the '6' position of the 4/8/6 switch (I get 4/8/8; but only seven of the eight work). I desoldered the pot and confirmed it's functionality with a DMM. I desoldered the LED and got it to light up on a breadboard. Finally I checked for continuity (via DMM) from pot 7's out to the corresponding pin on the 4017 so the signal should be physically capable of working.

But still no pot 7 functionality or led. 1-6 & 8 pots & leds work all day long making all kinds of crazy/cool tremolo sounds; not so much wah sounds but I was just using a clean, bedroom level sound so maybe it was there and I didn't notice...

Anybody got thoughts on what to check before I try a replacement chip? Thanks in advance.

[maysink]

bump

Any thoughts beyond swapping in a new chip? They're on a boat from Thailand so I got time to troubleshoot if better ideas are floating around out there.

[maysink]

Yep. New chip solved everything!

[PeterMorton]

Excellent!

[madbean]