PT2399 - min resistence ?

[electricco]

Hi, I'd like to build this circuit but i wonder what it will be the min and max resistence equivalent
on each PT chip when delay pot is 0 and pot is 50KB.

It is based on madbean delay circuit.

http://postimg.org/image/zdho7og5z/

[deadastronaut]

1k..

the 1k resistor will always be inline regardless..anything lower 'may' lock up the pt's..(though i haven't had this problem with 560r , but with 4 pt's)


with multiple pt's i usually go..

pin 6 to collectors, 

connect all base's together..which connect to your 'time' pot

then have 560r's on the emmiters...

just finishing up my 4 pt delay...

[electricco]

I'm following you on your new PCB runs ! great stuff !

But I'm referring to the image i've linked :-)

what is not really clear to me is the 6K8 resistor from power to delay pot..
Does it should be considered as well, or not ?
When the pot is engaged it change the delay... so min resistance should be 1K + 6K8

the emitter resistor won't be countend in this game, right ?

[deadastronaut]

re: 6.8k.


on my design i have 5volts to a 1k resistor to the time pot..

so yes i would include that too..

[electricco]

ok but I'm confused.
What it sound strange to me is that 7K8 produce a delay of 125ms for each PT and this would mean 250ms (approx)  as min delay.

I've it on breadboard and I can hear that min delay is close to an echo sound (less then 100ms  or close to that)


Is there someone that can clearly explain how the transistor stages works ?
...I'm guessing the PT see only 1K and the rest of stuff is current limiter...

[slacker]

The PT will see the 1k and 680 Ohm plus whatever resistance the transistor is. The 6k8, the pot and the other stuff attached the base controls how much the tranistor is turned on, the more it turns on the more current can flow through it so its resistance goes down. Sorry I don't know how you would calculate the resistance range of the transistor.