Feel like a winner today!

This last weekend I was determined to empty out my “box of fail” builds and try to breath some life into them. Today I decided to try to conquer a Madbean Zero Point SDX (Which is a beast) and I tamed that beast, slayed the dragon or tipped the cow. I got this PCB back in February 2014 and I populated it over a couple of days and then when testing it I was getting nothing but distorted delay repeats. I was very very green in February (now I am just very green) and had no idea where to start troubleshooting. I then revisited it in June thinking “this is the time I get this thing going” but I failed again. I replaced all the PT2399’s and I checked voltages and they looked fine so It went back in the “box of fail”.

Now, today! I set the PCB up on my test rig and got a tone going through it and started tracing out where the distorted repeats start in the circuit. I found the distortion was on pin 8 of IC2 PT2399 (Current control 0) and to my surprise I had a 10nF film cap instead of a 100nF film cap in C15. As soon as I popped in a 100nF cap everything was repeating clean as it should.

On the PT2399 the pin 8 (CC0) and pin 7 (CC1) are for “mod” and “demod”. Now I just need to figure out what they are used for and why did it produce distortion with a 10nf… but for now, ITS WORKING.

An old build sees the light of day and I finally feel like my troubleshooting skills are getting a tiny bit better.

Here is a shot of the PCB. Ever since I moved to the Panasonic film caps, these box caps are hard to look at. lol