PT2399 Tape Stop Effect

[Aleph Null]

I recall reading somewhere that it was possible to get a PT2399 delay to do a "tape stop" effect where the delayed signal slows to a stop. For the life of me, I can't find the forum post anymore. I think it involved grounding a pin through a resistor, but I don't remember which pin or recommended resistances. Has anyone else hear of this? Can you point me to a forum post somewhere?

[harryklippton]

Whoa. I'd be interested in this too

[madbean]

Yup. Use a 22R 1/4W resistor attached to pin1 of the PT2399. Put the other end to a momentary switch so that the switch grounds that resistor when pressed. When activated the resistor will drain current from the 5v regulator to ground. The result is the delay repeats will continuously drop pitch. After a few seconds the PT2399 will stop working but once you release the switch it will go back to normal operation.

I included this mod on the Loophole project many years ago. It's really fun to play with.

[Aleph Null]

Yup. Use a 22R 1/4W resistor attached to pin1 of the PT2399. Put the other end to a momentary switch so that the switch grounds that resistor when pressed. When activated the resistor will drain current from the 5v regulator to ground. The result is the delay repeats will continuously drop pitch. After a few seconds the PT2399 will stop working but once you release the switch it will go back to normal operation.

I included this mod on the Loophole project many years ago. It's really fun to play with.

Thank you! I knew I had read about this somewhere. I'm working up a delay design and I wanted to experiment with this.

[flanagan0718]

Huh. That’s a neat trick!


Sent from my iPhone using Tapatalk

[jessenator]

The result is the delay repeats will continuously drop pitch. After a few seconds the PT2399 will stop working but once you release the switch it will go back to normal operation.

Is there a way to control the drain time, by chance? Different resistor value?

Thanks.

[Aleph Null]

The result is the delay repeats will continuously drop pitch. After a few seconds the PT2399 will stop working but once you release the switch it will go back to normal operation.

Is there a way to control the drain time, by chance? Different resistor value?

Thanks.

I haven't had a chance to experiment with this yet, so I don't know for sure, but a smaller resistor value should result in a faster drain time. Since the supply voltage effects the clock speed, there may be a minimum drain time/resistor value that's necessary to keep from locking the clock up.

[jessenator]

I haven't had a chance to experiment with this yet, so I don't know for sure, but a smaller resistor value should result in a faster drain time. Since the supply voltage effects the clock speed, there may be a minimum drain time/resistor value that's necessary to keep from locking the clock up.

Ah, interesting. It'll be interesting to experiment with! Let us know what you find.

[jessenator]

I haven't had a chance to experiment with this yet, so I don't know for sure, but a smaller resistor value should result in a faster drain time. Since the supply voltage effects the clock speed, there may be a minimum drain time/resistor value that's necessary to keep from locking the clock up.

Not a rush or anything, but I'd be curious what you found. I posted over in my project thread, but I plopped a 100R trimmer and Bean is right, around 50–55Ω is when things happen. IDK if it's my particular circuit, but I wonder if I got something wrong—totally probable
https://drive.google.com/file/d/1mVYPFrnkgu1TJbdCzpUhGxri1bzE-Gas

Like I say, I'd be curious what your build and take on the "stop" effect sounds like.

[Aleph Null]

I've got the main circuit on the breadboard right now. I'm ironing out the wrinkles of the main feature before testing the tape stop.

[Aleph Null]

I was able to test the tape stop. It works, but it takes several seconds to wind all the way down. 10 ohms works a little faster, but still takes a few seconds. 1 ohm shuts things down very quickly and seems to lock up the chip sometimes, or at least, it doesn't recover as gracefully.

[jessenator]

Interesting… I must have something screwy on mine, because all it does is that warp-like thing briefly and nothing else…

[jessenator]

I wonder if it's my alteration that got me into trouble…

This is what I had originally:

(+5V is pin 1)


I adjusted the layout to be this way:



Or if there's something wrong with my layout—wouldn't surprise me.

[mauman]

I wonder if it's my alteration that got me into trouble…

Your full-scale layout doesn't match the close-up of the mod.  The close-up looks right, the full-scale doesn't.

[Aleph Null]

I wonder if it's my alteration that got me into trouble…

This is what I had originally:

(+5V is pin 1)


I adjusted the layout to be this way:



Or if there's something wrong with my layout—wouldn't surprise me.

The close -up looks reasonable to me. I don't know how much use the trimmer will be though. The tape stop was mostly effected by the delay time. I'd slot in a 10 ohm resistor and call it a day.

That said, my 10 ohm resistor got HOT!, so implementing this at all might cause undue wear and tear on your PCB.