Muskett Fuzz Clone Problem

[Vlad7329]

Hello everyone.

I am building a Muskett clone. I am using this schematic from Kit Rae's website.


I made it on PCB which I made myself by etching.
I copied the schematic and added true bypass to it. (3pdt button)

So the problem is the following:
The pedal is too quiet and low gain. I checked all the components values and placement several times, also checked for bad solder joints and didn't find any problems.
Also i started with 2n5089 transitors, then I though maybe hfe was too low and swapped 2 of 5 transistors for mpsa18. It didnt change anything - it's still too quiet and low gain. Transistor pins are also placed correct.
Should i try swapping other 2n5089 for mpsa18?

Also I am not planning to use pedal clip in the battery, only power supply socket, but now as i am testing the build I am using 9V battery. the voltage is 8.87 volts. Can it be too low?

[iainpunk]

that battery is on the lower side of ''just owkay'', i recommend testing with a power supply to ensure maximum stability.

can you measure the Collector voltages of the transistors? they could give us a clue of whats going on.

cheers

edit: https://www.diystompboxes.com/smfforum/index.php?topic=29816.0
check this link, its one of the pinned threads here

[antonis]

No tranistor issue..
(it should work fine even with 2N3904 or 2N5088..)

Lift R27(22k) lower leg up (no GND connection) to see what is happening..
(possible pop issue can be faced down later on..)

[Vlad7329]

iainpunk, antonis - thank you very much for the replies.

I dont have a power supply yet, need to build it still. All I have on hands is the battery. by the way it measures 9.09V when out of clip so should be okay.
So I did some measurements suggested on the page iainpunk linked.

Voltage at the circuit board end of the red battery lead = 8.87V
Voltage at the circuit board end of the black battery lead = 0V

Q1
C = 5.58V
B = 1.39V
E = 0.88V

Q2
C= 4.61V
B= 0.73V
E= 0.13V

Q3
C= 4.61V
B= 0.73V
E= 0.13V
(same result as Q2)

Q4
C=4.07v
B=0.65V
E=0.04V

Q5
C =3.62V
B =0.79V
E =0.2v

Then diodes
D1 POS 4.6V NEG 0V
D2 POS 4.2V NEG 4.6V
D3 POS 4.6 NEG 4.25
D4 POS 4.25 NEG 4.6

Q4 and Q5 are MPSA18
Q1-Q3 are 2n5089

Voltage on electrolytic cap + 0.65V, on the minus  it's 0V

Also electrolytic cap was replaced for 2.2uF instead of 1uF in the schematic. I did it when i first tested the pedal and it sounded bad. I thought that i could have overheated the cap with my iron.  Telling it for full disclosure.

[antonis]

All voltages are fine..!! 
(just for your info, diodes POS readings reflect respective collectors voltages and NEG readings are POS minus diode forward voltage drop ones, which in turn verifies C6 & C7 good working condition - DC "isolation..)

P.S.
Now, could you plz disconnect one leg of R27 now..??

[Vlad7329]

Hi Antonis.thanks for your suggestion, and I did as you told: I soldered the ground leg of r27
Here is a  video. In it, I first play with pedal off, then I turn it on and you can hear it still gets super quiet, although I think after disconnecting the leg, it sounds like there is more fuzz to it.
Then I turn the pedal off again and it becomes MEGA loud (you can't hear it in the video due to compression):

https://youtube.com/shorts/jQ5Qx4ydBW4?feature=share

I think I'll just swap the remaining transistors and see what happens

[Ben N]

There really shouldn't be any problem with a 2N5089/2N5088/MPSA18, but maybe try an MPSA13 in the recovery position? (That should really be too much gain, but...) Also, check the input and output of each stage with a signal tracer to see exactly where you are having a drop off, and if that doesn't help, try disconnecting and reconnecting the clippers one at a time.

[Vlad7329]

There really shouldn't be any problem with a 2N5089/2N5088/MPSA18, but maybe try an MPSA13 in the recovery position? (That should really be too much gain, but...) Also, check the input and output of each stage with a signal tracer to see exactly where you are having a drop off, and if that doesn't help, try disconnecting and reconnecting the clippers one at a time.

Hi Ben,
Could you elaborate on type of signal tracer?

[duck_arse]

dear Vlad, might we see photos of what you have built, nice, close and clear, so that we can see your resistor colour bands, just as an example? and do you have a layout diagram we might gaze upon, for placements?

[Ben N]

Also, check the input and output of each stage with a signal tracer to see exactly where you are having a drop off, and if that doesn't help, try disconnecting and reconnecting the clippers one at a time.

Hi Ben,
Could you elaborate on type of signal tracer?

Sorry, I meant an audio probe. https://www.diystompboxes.com/pedals/debug.html

[antonis]

I think after disconnecting the leg, it sounds like there is more fuzz to it.

Signal (amplitude)..

As it ts (with R27 in place), input impedance is R27//R28//R31//(h_FE+1)*R29 -> about 15k..
(for a signal source of 15k output impedance, you have 50% amplitude domination..)

Without R27 (or for a much higher value), input impedance is about 30k hence 33% amplitude domination..

P.S.
Plz do what duck_arse asked you for 'cause pics are always enlightening..

[Vlad7329]

There are some pictures of what I've built

[antonis]

I'm not able to presicely follow layout but ground plane has a couple of etching discrepancies..