Big Muff EC3003-A doesn't work

[Amitay3333]

Lately I have built the old version EC3003-A Big Muff... it's true bypass and works when it's off but when it's on I got nothing, pure silence I have chaked the switch and the Led and everything works great i chaked bad connections and bridge and I got nothing maybe someone can help me here, this is the voltage reading:

pin:   sustain:   volume:   tone:
1   0   0   4.445
2   0.012   0.022   2.068
3   0.02   0.046   0.837


Pin:  Q1           Q2            Q3         Q4
E    0.032    0.121   0.109   0.642
B    0.64           0.731       0.718       1.248
C   4.468   4.528   4.484   4.584

[Amitay3333]

[antonis]

All BJTs measurements are fine..!!
Both Sustain and Volume pots measurements are meaningless 'cause they're DC isolated..
(what you measure is voltage drop due to respective caps discharge..)
Tone pot measurent is also OK (depending on wiper setting) 'cause it takes DC voltage from Q3 Collector to GND via R18 & R19..
(although, lug1 voltage should be stand lower - at about 4.45V for a high impedance DMM..)

So, focus on IN-OUT wiring and 3PDT switch PCB..

[soggybag]

Make the audio probe and follow the signal through your circuit startinging from the input. This will tell you a lot.

The audio probe is a cap connected to the tip of a jack going to an amp. Connect the sleeve to ground in your circuit.

[antonis]

The audio probe is a cap connected to the tip of a jack going to an amp. Connect the sleeve to ground in your circuit.

Lazy enough to post a schematic..?? 

https://www.google.com/search?channel=nrow5&source=univ&tbm=isch&q=audio+probe+schematic&client=firefox-b-d&fir=8-YxP8DQVohVgM%252CBFueo78fOvAeFM%252C_%253BDMpyY4lYzzc5xM%252CEhUm7dVPVYK1NM%252C_%253BlLhWHkbFLBapdM%252CcRFgIRpa3pXU_M%252C_%253BlNYkjDqXAJCLXM%252CEhUm7dVPVYK1NM%252C_%253BcxNo1rmZGbq65M%252Cqv-sOdYBEarAbM%252C_%253BlG1H5Lfx5ZiA4M%252Cnma8UtR_ay-cZM%252C_%253BmfgwXqHg_nb3MM%252Cqv-sOdYBEarAbM%252C_%253BYVaRicToHP0pyM%252CRi42Lx9Fiqbk4M%252C_%253Bqa3kdZsuV-yAGM%252CsfqlJ-sGA7T9bM%252C_%253BUnxN-vpvwt0mNM%252C1W0JyouCqWL_RM%252C_&usg=AI4_-kQb-dWfhEqyWWp6UEawkd_MoT5aCw&sa=X&ved=2ahUKEwiqj8Haqpb3AhXCzKQKHWoqAUQQjJkEegQICRAC&biw=1400&bih=925&dpr=1

[Amitay3333]

Make the audio probe and follow the signal through your circuit startinging from the input. This will tell you a lot.

The audio probe is a cap connected to the tip of a jack going to an amp. Connect the sleeve to ground in your circuit.

Thanks, I did the Audio probe averything sound right until I got between R23 and C13 when the audio goes silent... I replaced both resistor and cap and still it didn't work maybe someone got an idea?

[Ben N]

So you do have signal at the collector of Q4, but not on the other side of R23? There must be either a bad solder connection or a short to ground somewhere near the end of the circuit. Luckily, the problem is localized to the circuit between R23, C13, the volume pot and the bypass switch. Check for continuity at each component to the adjoining components on the schematic, and to ground. If you find no continuity where there should be continuity, you've found your break in the signal path. If you find continuity to ground where there should not be, you've found your short.
You might also want to confirm the values of R23 & your volume pot, though even a mistake there wouldn't likely kill the signal entirely.

[Amitay3333]

So you do have signal at the collector of Q4, but not on the other side of R23? There must be either a bad solder connection or a short to ground somewhere near the end of the circuit. Luckily, the problem is localized to the circuit between R23, C13, the volume pot and the bypass switch. Check for continuity at each component to the adjoining components on the schematic, and to ground. If you find no continuity where there should be continuity, you've found your break in the signal path. If you find continuity to ground where there should not be, you've found your short.
You might also want to confirm the values of R23 & your volume pot, though even a mistake there wouldn't likely kill the signal entirely.

I already chaked connection with everything... the connection seems ok nothing goes to ground or to other component and my soldering seems fine... I don't know what else to do mann

[Amitay3333]

So you do have signal at the collector of Q4, but not on the other side of R23? There must be either a bad solder connection or a short to ground somewhere near the end of the circuit. Luckily, the problem is localized to the circuit between R23, C13, the volume pot and the bypass switch. Check for continuity at each component to the adjoining components on the schematic, and to ground. If you find no continuity where there should be continuity, you've found your break in the signal path. If you find continuity to ground where there should not be, you've found your short.
You might also want to confirm the values of R23 & your volume pot, though even a mistake there wouldn't likely kill the signal entirely.

I already chaked connection with everything... the connection seems ok nothing goes to ground or to other component and my soldering seems fine... I don't know what else to do mann

Mann I Found it!
As usual child mistake,  fault drawing... in schematic C13 aren't supposed to be attached to the 9v supply its need to be attached to pin c on Q4
Ohh  mannnn
Thanks to everyone's help... at list I learned something about fault diagnosis, I'm happy with the result(:


Regards and healthiness
Amitay Kehaty.

[anotherjim]

Good catch. Scheme error is obvious now we know. Also, good to see the filtering in the power section.

[antonis]

Scheme error is obvious now we know.

Sometimes eye sees what should be considered obvious..
(like output cap on Collector..)

[Ben N]

So you do have signal at the collector of Q4, but not on the other side of R23? There must be either a bad solder connection or a short to ground somewhere near the end of the circuit. Luckily, the problem is localized to the circuit between R23, C13, the volume pot and the bypass switch. Check for continuity at each component to the adjoining components on the schematic, and to ground. If you find no continuity where there should be continuity, you've found your break in the signal path. If you find continuity to ground where there should not be, you've found your short.
You might also want to confirm the values of R23 & your volume pot, though even a mistake there wouldn't likely kill the signal entirely.

I already chaked connection with everything... the connection seems ok nothing goes to ground or to other component and my soldering seems fine... I don't know what else to do mann

Mann I Found it!
As usual child mistake,  fault drawing... in schematic C13 aren't supposed to be attached to the 9v supply its need to be attached to pin c on Q4
Ohh  mannnn
Thanks to everyone's help... at list I learned something about fault diagnosis, I'm happy with the result(:


Regards and healthiness
Amitay Kehaty.

מדהים!