Brown Betty slowly dying

Chas Grant

Well-known member
Looking at the schematic, your bass pot is in the same part of the circuit as C12, since you ruled the pot bad, remove it then commence troubleshooting the pedal dying. It is hard to troubleshoot 2 bad components in the same circuit. Be careful removing pot! It’s very risky to do and easy to damage board. If you haven’t done it before, consider cutting the leads of the pot then remove the cut leads one by one
 

Chas Grant

Well-known member
One other thing, after removing pot, see if dying issue still exists! The bad pot could be the culprit. The pedal will work without the bass pot in the circuit, may not sound to good, then again it just might. How do you think mods come about?
 

TSReppe

Active member
One other thing, after removing pot, see if dying issue still exists! The bad pot could be the culprit. The pedal will work without the bass pot in the circuit, may not sound to good, then again it just might. How do you think mods come about?
Yeah I’m down to two theories. The bad pot or the two resistors that are 22k instead of 20k. Those are have to do with voltage and it sounds like a voltage issue, but how a jumpstart at c12 gets it back to life will be a bigger mystery.
 

PJS

Active member
Having those resistors at 22k is going to change the Vref voltage by a very small amount. I doubt it is going to make any noticeable difference to the sound.
 

TSReppe

Active member
Having those resistors at 22k is going to change the Vref voltage by a very small amount. I doubt it is going to make any noticeable difference to the sound.
That was my thinking when using them, but I’m out of ideas now. Changed the pot. Tested the new pot before putting it in, and yes, it had a difference when turned, but when I put it in it reacted like the other one. No difference on measurements when turning the pot and no difference to the sound. I’ll try the resistors, but if that doesn’t work I think I’ll cut my losses, salvage parts and move on to the next project.
 

music6000

Well-known member
That is the wrong thought of thinking unless you have Money to Burn.
Members here will help you through it but if you want quit, I can't guarantee you will get Help with your next project.

Here is something that could be an Issue also :
What Is This.jpg
 

Chas Grant

Well-known member
R32 and R35 at 22K is fine and should not affect the circuit. They are the top resistors of a voltage divider suppling voltage to the non-inverting inputs of an op-amp being used as a buffer for the reference voltages. We will assume that voltage after R30 is 8V, due to voltage drop of D5 and R30. With the resistors at 20K Vref/Vdd will be 4.19V, with resistors at 22K Vref/Vdd will be 4V. So .19 volts difference will not have much of an affect on operation of circuit. Part substitutions like this have been going on forever in the pedal world. A manufacture will run out of one part but keep producing pedals using the closest value they have on hand to keep production running. Just look at how many versions of the Big Muff Pi there are.
 

TSReppe

Active member
R32 and R35 at 22K is fine and should not affect the circuit. They are the top resistors of a voltage divider suppling voltage to the non-inverting inputs of an op-amp being used as a buffer for the reference voltages. We will assume that voltage after R30 is 8V, due to voltage drop of D5 and R30. With the resistors at 20K Vref/Vdd will be 4.19V, with resistors at 22K Vref/Vdd will be 4V. So .19 volts difference will not have much of an affect on operation of circuit. Part substitutions like this have been going on forever in the pedal world. A manufacture will run out of one part but keep producing pedals using the closest value they have on hand to keep production running. Just look at how many versions of the Big Muff Pi there are.
Sounds about right. Couldn’t imagine that being the issue, but for now it’s all I’ve got.
 

TSReppe

Active member
That is the wrong thought of thinking unless you have Money to Burn.
Members here will help you through it but if you want quit, I can't guarantee you will get Help with your next project.

Here is something that could be an Issue also :
View attachment 7702

It’s just frustrating dude :)
In the picture it looks close, but those points has never touched and the 3pdt is soldered to the spesifications of the build docs. At the very least I’ll step back a bit before looking at it again.

What I know is this:
The pedal works fine for about 10-15 minutes before it starts dying. It does so slowly and it sounds like voltage dropping off. First it gets muddier, goes over to sounding more like a fuzz, starts gating before eventually going totally quiet. The two ways of getting it back to life is either unpligging and plugging back in the power supply, or jumpstarting it by touching the two solderpoints of C12 simoultainously. I don’t get this effect by touching anywhere else.

Things I’ve tried so far is replacing C12, replacing the bass pot, which is in the same part of the circuit and replacing IC4. There was one loose cap, but that has been taken care of. DC-input has also been replaced.
 

music6000

Well-known member
It’s just frustrating dude :)
In the picture it looks close, but those points has never touched and the 3pdt is soldered to the spesifications of the build docs. At the very least I’ll step back a bit before looking at it again.

What I know is this:
The pedal works fine for about 10-15 minutes before it starts dying. It does so slowly and it sounds like voltage dropping off. First it gets muddier, goes over to sounding more like a fuzz, starts gating before eventually going totally quiet. The two ways of getting it back to life is either unpligging and plugging back in the power supply, or jumpstarting it by touching the two solderpoints of C12 simoultainously. I don’t get this effect by touching anywhere else.

Things I’ve tried so far is replacing C12, replacing the bass pot, which is in the same part of the circuit and replacing IC4. There was one loose cap, but that has been taken care of. DC-input has also been replaced.
Do a Continuity check with the Matching colours/ letters & check all the solder pads Highlighted in the Circles/ Letters :

Updated with Matching Letters
Brown Betty Continuity Check.jpg
 
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zgrav

Well-known member
Would seem like the continuity-test on my cheap ass dmm isn’t working. I need to get that sorted out or see if I can borrow one to make these tests.
you can set the DMM to measure resistance and then check those points to see if you get a zero reading
 

zgrav

Well-known member
continuity means you should have zero readings between those same-color points. if you are not getting zero readings that could explain why your continuity test was not sounding either.
 
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