21st Century ADSR - Not working!

[numbernone]

Sad to report my first failure at a Thomas Henry design, after several out of the gate working perfect experiences I guess it was bound to happen.

Last year I spent a good long time designing a board for the ADSR from the lovely 21st Century book. I have green/yellow/redlined the schematic dozens of times and revised the board as needed. I have only now gotten around to building one, and alas it does not function, and to further the despair I realize I have no earthly idea how this circuit functions, nor where I should begin to debug it.

1. I have thoroughly checked the layout against the schematic countless times, and find no errors nor improperly polarized componenets etc.

2. I am using bananas, and at the suggestion of Scott Stites, am intending to use the C7K 7211 switch to toggle between trig/gate/both. I do not currently have the switches, and am manually connecting the appropriate wires while testing.

3. I still dont have a scope!! I know I know I need one! My meager test gear is my trusty FLuke meter and my ears.

4. All the chips are getting the proper power and ground in the proper places.

5. What kind of gate is this design looking for? 5V?

6. One thing that has consistently thrown me forever is the wiring of pots that are indicated in the schematic with only the outer lugs connected and the old angled arrow thru the center. what is the proper way to wire these guys.

7. So if some kind soul can throw me a bone and give some clue where the first place to look for some signs of life might be I would much appreciate it.

Thanks!!

Can't wait to see what TH has in store for us this summer.

[magman]

I'll answering your question number 6 first.

There are two main ways for wiring up a pot, either as a potential divider or as a variable resistor.

The name pot is short for potentiometer and this gives you a hint what the device was originally designed for - to act as a potential divider. The two outside connections are normally the two ends of the resistance element in the pot (these are often referred to as CW and CCW for clockwise and counterclockwise connections), the middle connection is know as the wiper. When you turn the shaft of the pot, you are actually mechanically moving the wiper against the resistance element. In the AS21C ADSR circuit, his is how R8 (the sustain control) is used, the wiper being connected to R15, the other legs being connected to R3 and Ground.

You can also wire a pot as a variable resistor. This effectively only used 2 connections on the pot, one end of the resistance element and the wiper, but is common to connect the other end of the resistance element to the wiper (short them effectively). This is how R14 (Attack), R15 (Delay) and R16 (Sustain) should be used in the AS21C ADSR.

I hope this explanation helps, but if you are still struggling, I can dig out some pictures of one of the front panels I recently wired which shows both types of connection.

Good luck on getting your ADSR working

Regards

magman

[slo]

You can test the ADSR with a logic probe a fair bit. I've built 2 and 1 failed due to a bad transistor. I checked with the probe to make sure all transistors were switching with a gate/trigger applied. Follow the pulse to the 555 to make sure it gets there. Also, I built mine with the switching jacks which this circuit needs, I know there is a work around for bananas, but I can't get my head around that. Gate/Trigger needs the V+ applied to transistor base when you only use one jack. Hope this helps.

George

[numbernone]

Thanks George, its a start for sure. Spent some time trying to digest the datasheets for the 555 and the 4016, getting some idea of whats going on here. As far as the switching jacks go, I am just manually connecting the the points that would otherwise be connected/disconnected by the plugs, ultimately the 7211 will swap between the 3 possible states.

Keep ya all posted...