Author Topic: Rustbucket Incorrect Trace?  (Read 256 times)

dobo2001

  • Diode Destroyer
  • *
  • Posts: 27
    • View Profile
Rustbucket Incorrect Trace?
« on: March 29, 2020, 07:18:43 PM »
Been dealing with a faulty Rustbucket for awhile, and I've come across something which doesn't seem right.

Currently getting a super distorted signal out of Pin 1 of IC1, and I was reflowing some of the joints and checking continuity of the parts around the IC and noticed something weird in the R2/3/4 area. I think there might be an incorrect trace on the PCB between R4 and R2? I've attached picture of the back of the board along with an annotation on the trace diagram which shows where I see the trace. I am also measuring continuity between these two points, which seems incorrect. Would love some guidance here, thanks!

Also, currently, all voltages for IC1 are correct with the ones provided in the build doc.
« Last Edit: March 29, 2020, 07:21:23 PM by dobo2001 »

madbean

  • Administrator
  • Electron Doctor
  • *****
  • Posts: 9434
  • Brian
    • View Profile
    • madbeanpedals
Re: Rustbucket Incorrect Trace?
« Reply #1 on: March 29, 2020, 08:23:03 PM »
Take a look at the schematic. What are R2 and R4 both connected to? See why you have continuity there?

BTW - I'm not intending to be flippant. Just saying sometimes you need to cross-reference board and schematic to get the full picture (this is the process I go through when I'm trying to solve problems, myself!)

In this case both resistors are connected to the ground pour on the bottom which is why you see/measure them having continuity. The ground plane isn't shown on the trace diagram since it would just make the whole thing look like a mess.

Now, for you distorted signal, can we see the top of the board right in that area?  Do both R3 and R4 have brown/green/black/orange bands? 
I own madbeanpedals (duh). I am part owner of Function F(X).

dobo2001

  • Diode Destroyer
  • *
  • Posts: 27
    • View Profile
Re: Rustbucket Incorrect Trace?
« Reply #2 on: March 29, 2020, 09:29:13 PM »
Take a look at the schematic. What are R2 and R4 both connected to? See why you have continuity there?

BTW - I'm not intending to be flippant. Just saying sometimes you need to cross-reference board and schematic to get the full picture (this is the process I go through when I'm trying to solve problems, myself!)

In this case both resistors are connected to the ground pour on the bottom which is why you see/measure them having continuity. The ground plane isn't shown on the trace diagram since it would just make the whole thing look like a mess.

Now, for you distorted signal, can we see the top of the board right in that area?  Do both R3 and R4 have brown/green/black/orange bands?

Yep. Looked at the picture right after I posted it and realized what I overlooked. I think I need to get out of my house.

As for R3 and R4, they both are 150K, double checked the color code along with measuring with the multimeter. Attached a photo of the top of the board (took the rest of the ICs out to try and isolate the problem).

dobo2001

  • Diode Destroyer
  • *
  • Posts: 27
    • View Profile
Re: Rustbucket Incorrect Trace?
« Reply #3 on: March 30, 2020, 09:25:36 PM »
Take a look at the schematic. What are R2 and R4 both connected to? See why you have continuity there?

BTW - I'm not intending to be flippant. Just saying sometimes you need to cross-reference board and schematic to get the full picture (this is the process I go through when I'm trying to solve problems, myself!)

In this case both resistors are connected to the ground pour on the bottom which is why you see/measure them having continuity. The ground plane isn't shown on the trace diagram since it would just make the whole thing look like a mess.

Now, for you distorted signal, can we see the top of the board right in that area?  Do both R3 and R4 have brown/green/black/orange bands?

Did some reflowing and I've tracked a problem back to the CD4047. When it isn't installed, signal passes through the MN3007, albeit without any effect, however, when it is installed, it turns the signal into a static at the MN3007. Without the CD4047 installed, all the pins on the socket have the correct continuity, but when it is installed, all of the pins have continuity to ground. Voltages are correct however.

dobo2001

  • Diode Destroyer
  • *
  • Posts: 27
    • View Profile
Re: Rustbucket Incorrect Trace?
« Reply #4 on: April 02, 2020, 08:13:18 PM »
Some more info regarding the problems with IC5:

Tried it as well with the MN3007 removed, and the CD4047 still produces the static noise. I'm fairly sure the CD4047 is causing the problems, as the signal arrives normally at Pin 3 of the MN3007, as well as pin 2 of the Bias trimmer, however, it leaves the MN3007 as the static.

Pins 1, 2, and 3 of IC5 also produce the static, along with pin 11. For some reason, when the CD4047 is installed, all of the pins have continuity to ground, something which stops when it isn't in there. Reflowed all the joints for the IC and around it, no change. Voltages are what they're supposed to be at.