Spirit Box only dry signal with some noise

[fxwiegand]

My spirit box build that I started a while ago doesn't seem to work properly. LED and Bypass work absolutely fine but when I turn the pedal on it only introduces some noice to the dry signal, its almost like its still in bypass. Also the PT2399 is getting insanely hot. I just reflowed all components one more time to make sure everything is right. I know I could have used some better caps than the small ones but that was all I had on hand when I started this build. Would it make sense to change those for proper ones like the 474s? Thankful for any help!

 

[Danbieranowski]

Where did you get the components (the 2399 etc) from?

 

[daeg]

Did you use the right voltage regulators? Can you measure the voltage at the PT2399 V+?

 

[fxwiegand]

I think I double checked the voltage regulators but I'll measure PT2399 V+ when I get back in my workshop at the weekend. The 2399 came from eBay so it may be bad. If that's the problem the fix should be at least pretty easy by replacing the IC.

 

[ADAOCE]

2399 is cheap and readily available at Tayda and other suppliers I would stay away from ebay as a general rule

 

[fxwiegand]

Yeah you're totally right about that I just had those still laying around so I didn't want to order new ones without even trying them. I already had some fake J201 from eBay that really drove me crazy at my Benson Preamp build where nothing was working. I got some real ones and suddenly everything was working perfectly. That was only some weeks ago (after starting the Spirit Box build) but it was definitely the moment where I changed my mind about where to source my parts (at least IC's/transistors).

 

[zgrav]

certainly try swapping the PT2399 chips, especially if you have them. but your symptoms sound more like a a problem on the board than a bad IC. look carefully at the parts that connect to the regulator to figure out why it gets warm to the touch.

 

[fxwiegand]

Did you use the right voltage regulators? Can you measure the voltage at the PT2399 V+?

I just measured V+ at the PT2399 and I got 4.996V so I guess that shouldn't be the problem right?

 

[fxwiegand]

certainly try swapping the PT2399 chips, especially if you have them. but your symptoms sound more like a a problem on the board than a bad IC. look carefully at the parts that connect to the regulator to figure out why it gets warm to the touch.

I just tried swapping the PT2399 (same batch as the one before though) but no difference, just the dry signal like in bypass mode. Still waiting for other PT2399's to come.

 

[zgrav]

When you swap in different Pt2399 chips, do they all get hot when you apply power to the circuit? Does your voltage regulator get hot? I think you need to check the parts that connect to that chip for either a short from a solder bridge or a bad connection. That also likely explains why there is a problem getting any sound from that part of the circuit.

follow the suggestions you will see in many forum posts --

remove board, jacks and footswitch from enclosure

see if it works out of the enclosure (unlikely to make a difference here since you have dry signal already, but still worth checking)

post detailed photos of each side of the PCB, the in/out/power jacks, and the footswitch so the wired connections are clearly visible
If you only have dry signal when the board is engaged, you are not getting sound from either the PT2399 or the Belton brick. look at the schematic and concentrate of the part where the audio signal separates to go to those two chips up to where the audio is recombined with the dry signal. if you are not able to sort that out I suggest putting in a little time about learning to read schematics since that will benefit you every time you are troubleshooting a problem in a build.

You most likely have a bad solder connection or short that is stopping the sound either going to the delay chips or coming back from the delay chips to be mixed with your dry signal. you can use your DMM to check the connections between the parts in that part of the schematic, but it may be simpler to build an audio probe and start tracing the audio from Pin 7 of IC4 to it connects to the PT2399 and then through the Belton brick and parts to Pin 6 of IC1.

 

[fxwiegand]

Ok I just build an audio probe and my Signal seems to be lost at Pin 7 of IC4.2. I am getting sound at Pin 6 and between R10 and R11. No sound at the other side of R10, Pin 7 of IC4.2 and Pin 3 of the Benton Brick. That should mean that at least one of these Pins has a short right?

Edit: I was right! I resoldered the other side of R10 and Pin 7 of IC4.2 and cleaned a bit and the pedal works beautifully! Never been that happy before hearing a reverb. Thanks so much for your help!

 

[zgrav]

Glad you got it working! Nice job working through the problem.