Trouble with Cave Dweller build, VERY long delay

[matmosphere]

I'm trying to build a Cave Dweller. It's my second build and first on a PCB.

When I test the pedal it is very noisy and has really long delay time (2 seconds). No mater how I set the time knob I get the same delay. I tried switching the pt2399 for a different chip, just to make sure that was not the issue. Any advice about what to look at would be much appreciated.

[jimilee]

Solder bridges and have your tried a different pt2399?

[matmosphere]

Yeah, I tried a different PT2399. I don't see any solder bridges, but there are a few spots that have some excess solder.

[ddog]

Have you considered that the pot itself is broken?

[matmosphere]

I had not thought about that possibility. Can you test it without disconnecting it?

[gjcamann]

You could aligator clip a resistor (about half the value of the pot) across the 2 pins on the pot that are used (I think it only uses 2 pins)

[ddog]

I wasn't sure so I just tested it on an EgoDriver pot. I hooked up my DMM pins directly to the pot rather then the PCB but I guess it doesn't matter.

I tested between Lug 1 and Lug 2 and  the numbers changed with each pot rotation.  They weren't exactly in spec as I got 20k on a 10k pot but maybe thats the rest of the circuitry affecting the resistance. Try it out with Lug 1 and Lug 2 + Lug 2 and Lug 3 and see if the numbers change

[wgc]

Two seconds!!!  That's awesome, but I think you should somewhere near 600 ms?

Kidding aside it is probably a wrong part or short. Since it's your first fabbed pcb, make sure you didn't accidentally put a part leg in an adjacent hole, easy to do.

Also check the troubleshooting guidelines, post some pix, voltages etc and you'll be up in no time.

[midwayfair]

I didn't think the PT2399 even capable of delay times above about 800mS regardless of using the wrong part ...

Post a picture of the PCB. Take voltages. Read here.

[madbean]

Sounds like you could have the wrong value in R11. If you had mistakenly put a large value resistor there, it would cause long delay times, and the delay pot would seem ineffective. What color bands do you have on that one?

[matmosphere]

Here are some pics of the top and bottom of the board. I'll try to get the readings posted later today. Thanks everyone for taking the time to help out.

[RobA]

Check the value of R11. It could just be the lighting, but the multiplier band looks like it could be red or orange. It should be a 5.1k, so the band would be brown.

It's probably not the issue in this case, but I'd cut the leads closer to the PCB and reflow the joints. It cuts down on the possibility of stray random shorts and other issues.

[matmosphere]

The bands on R11 are green, brown (thicker band), brown, orange, brown.

[RobA]

The bands on R11 are green, brown (thicker band), brown, orange, brown.

That should put it at 511kΩ and it would make sense that this is the source of your issue. The spec sheet for the PT2399 indicates a 27.6k resistor gives a delay of 342ms with a THD of 1.0%, so a larger value than that is going to put it into a long delay and high noise. It would also be consistent with the pot not working much. The pot is sitting at about 10% of the combined value of R11 and the pot, so it can't change the delay time very much.

[Clayford]

mmm and R11 is a 5k1 resistor.... You should have hit the nail on the head, so lets double check those colours when you replace it. A proper 5k1 resistor is Green Brown Black Orange Brown (assuming the 5 band 1% you've given.)

edit: Lost my darned mind! bad color codes. I gave 510K