Troubleshooting a buzzing Rat.

[eh la bas ma]

Hello,

I am trying to help a friend with his Rat build.

https://www.musikding.de/docs/musikding/rat/RatV2_schalt.pdf

There is a signal in bypass, but with a buzzing noise in the background (almost as loud as the signal). When the circuit is engaged, I can't hear the signal, just the buzzing noise, even louder.

We had some trouble with a difficult soldering iron, The old solder was really hard to re-flow, I am concerned that the board might have been damaged by heat.

My friend's soldering skills were a bit rusty, so I did my best to re-do some suspicious soldering joints here and there.

here are some pics :

[ Edit : pictures deleted, they were unecessary and the problem is solved ]

I am having a hard time getting rid of the buzz, I am not even sure that the board is still ok...What do you think ?

Any help would be welcome !

[eh la bas ma]

Oh... and of course, here are some voltage readings :

DC jack+ = 9.44V
VB (measured on R9) = 2.5 V

OP07

1= 9.04 V
2= 4.57 V
3= 4.09 V
4= 0
5= oscillates between 0 to 2.5mV
6= 4.56 V
7= 9.14 V
8= 9.04 V

2N5458

G= 2.5 V
S= 3.1 V
D= 9.13 V

Edit: I notice that i can't have proper readings unless the circuit is engaged, otherwise the meter keeps oscillating, both on OP07 and on the transistor...this can't be a good sign, but i don't know for sure.

[GibsonGM]

Check ALL grounds; the buzz really sounds like a bad/missing gnd.  Cold solder perhaps.  No gnd on output jack, things like that.  Check for continuity on every gnd. 

Are you using a regulated supply to test the pedal?  Does it do this with a battery only? 

[eh la bas ma]

Check ALL grounds; the buzz really sounds like a bad/missing gnd.  Cold solder perhaps.  No gnd on output jack, things like that.  Check for continuity on every gnd. 

Are you using a regulated supply to test the pedal?  Does it do this with a battery only?

Thanks ! I'll check every ground, install a battery, and test the circuit with it, and report.

I am using a Truetone 1spot.

[GibsonGM]

I'd imagine it would be pretty noise free then (unless something is wrong, but other pedals would show same issue).   Probably a ground, just like unplugging something and leaving the cord on the floor - bzzzzz!     

Some don't use a 'wire ground' to the output jack and depend on the enclosure to ground it - if it comes loose (or is unboxed) there is no ground. Just one place to check.

[eh la bas ma]

All clear, thanks for the help !

It was really an easy fix...Wires color was inverted on the footswitch's jack OUT : blue is GND, black is tip. I was confused by the colors and wired the tip to the GND... To think that I was almost doubting the board, along with my friend's skills...I should be ashamed.

Everything is fine now, I am even considering some clever mods : my friend intents to use his Rat with keyboards and synths...All your suggestions are welcome !

[duck_arse]

rule number one: meter your jacks and footswitch before you first apply power.