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Hello. I am new at pedal building. In fact this is the second time I try to build the blues buster. First time I damaged a board and now I am restarting with better welder and tools. I appreciate any support of the community to help identify the problem and also help me learn the right questions to ask.
There is sound when pedal stomp is off. There is no sound when it is on unless I pluck the strings quite hard. Then the led lights up and a extreme distorted sound comes through quickly and then stops as the signal level is lower. 5is effect happens on both positions of SW1.
almost like the clipping is too hard..
attached is the board. Maybe someone can help me identify the error? Thank you
I thought it may be useful to know the parts list
C1, C3 – 56n
C2 – 47p
C4 – 15n
C5, C6 – 220n
C7, C8 – 10n
C9 – 1u
C10, C11 – 100u
D1, D4, D3 – 1N914
D2, D5, D6 – LED
D7 – 1N4001
IC – 4558
R1, R2 – 1M
R3, R7, R8 – 4k7
R4, R5, R6 – 3k3
R9, R12, R13 – 6k8
R10 – 560K
R11 – 1k
R14, R15 – 47k
Treb – T50k
Tone – B25k
Volume – A100k
Drive – B250kthanks
Double check R10? Build doc lists 220kΩ.
Thank you. I see. I bough the kit from PedalParts and Kits and their kit comes with 560k for R10.
I don’t have any 220k to try.
The way I read the schematic when I switch SW1 to b position it bypasses R10. Is this right?thanks
Your R3 looks like 47K I think you’ve mixed it up with R15
R15 looks like 4K7 and should be 47K
R3 looks like 47K and should be 4K7
Easy enough to do they’re very similar colour bands
That would affect the op amp biasing
From your description of the fault it does sound like the op amp is misbiased
Easy enough to check take voltages on the IC input and output pins you should get half power around 4.5v
Pins 1,2,3,5,6,7 should have around 4.5v With pin 4 ground 0v and pin 8 power +9v
Just for info when troubleshooting the very first thing to do is visually check all components are the correct value and orientation youll find resistor colour band charts on the guides page
Using a 560K in place of a 220K would increase the gain significantly but shouldn’t mis bias the op amp afaik that resistor would be in circuit regardless of the switch position the switch looks like it connects the diodes in and out
Hello Billy. I can’t tell you how many times I went through the chart and the board to see if I made a mistake. I must’ve been looking for bigger mistakes. These resistors look so much alike.
I will resolder and post here the result. Thank you so much.
“Using a 560K in place of a 220K would increase the gain significantly but shouldn’t mis bias the op amp afaik that resistor would be in circuit regardless of the switch position the switch looks like it connects the diodes in and out”
Understood, thanks Billy!
I’m not 100% on whether it would be too much Fig
Hence the afaik
As you know calculating gain with a 220K feedback resistor and 4K7 input resistor gain would be 47 and with a 560K = 119 for an inverting op amp set up
So over double fairly significant as far as I know the gain would be increased and bandwidth reduced but seeing as they can multiply gain in 000s I don’t think it’d affect or destabilise it massively but I don’t know for sure
Wilkie will know tell us Ray
This solved. Thank you very much
Billy solved it! Your calculations are correct.
Billy. You were really very helpful and I actually got an email from Pedal parts amd kit. They are sending me a 220k replacement. This is really great community and great service. I am happy to start this journey with you all.
As a feedback to the gain issue. The gain is very high but not unusable. I am sure there is use for this. The pot at minimum has the sound I expect should be at maximum gain.
thank you all again
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