Green Russian Big Muff Build Issues!

[Benjamos86]

Hey all,

I just finished up a green russian big muff build, using a layout from Dirtbox Layouts. I used the "MOJO Layout" that can be seen at the below link (the second layout option on the 30x14 stripboard):

https://dirtboxlayouts.blogspot.com/2019/06/electro-harmonix-sovtek-russian-big-muff.html

Went to plug it in last night and I'm definitely having some problems!

Bypass signal is fine, but when pedal is engaged, the signal essentially drops to almost nothing. With everything maxed out, I get the faintest of signal through the pedal, but there is definitely an issue.

The LED works fine, and I see 9.3V when checking for voltage at the LED.

I measured my transistor voltages, and here is what I am seeing:

q1 c, b, e = 0.56V, 1.22V, 0.54V
q2 c, b, e = 1.23V, 214mV, 0.1mV
q3 c, b, e = 4.54V, 0.73V, 131mV
q4 c, b, e = 6.04V, 1.54V, 0.95V

Transistors are: Motorola 2N5089

Something is definitely wrong, and I'm questioning whether the layout itself has issues, or if I managed to mess something up along the way.

I triple checked that I followed the layout as it is shown. I'm wondering if I have a bad solder joint, damaged copper pad, or a short on the board somewhere.

Any tips are welcome and much appreciated!

[antonis]

Chgeck for correct pinout..

[Benjamos86]

Chgeck for correct pinout..

Thanks antonis! I assume you mean pinout of the transistors? I did double check and they should be in the proper orientation.

However I did just notice, from looking at the below schematic, the 2.7k resistor tied to the emitter of q1 appears to instead be tied to the emitter of q4 on the layout I posted/followed. So I have 390 ohm off the emitters of q1, 2, and 3, and 2.7k off of q4

http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part3.html

This also means I have the 10k resistor off the collector of q4, rather than q1, and 12k off the other collectors.

Am I on to something here or am I thinking about this wrong?

[antonis]

Your layout Q1/Q4 orientation is OK..
(there is a confusion in Big Muff transistor numbering.. never mind..)  

Could we see some pics of your build..??
(Q2 voltages are way off and Q1 seems dead-shorted..)

[Benjamos86]

Some other measured voltage values:

D1:
Anode = 1.23V
Cathode = 1.03V

D2:
Anode = 1.03V
Cathode = 1.23V

D3:
Anode = 4.53V
Cathode = 4.29V

D4:
Anode = 4.29V
Cathode = 4.53V

D1-D4 are Fairchild 1N914B

D5:
Anode = 9.38V (Same as supply)
Cathode = 9.18V

D5 is 1N5817

Confirmed I see 9.38V across power supply jack.

Confirmed I see 9.18V on the positive side of the 47uF electrolytic cap

[Benjamos86]

Your layout Q1/Q4 orientation is OK..
(there is a confusion in Big Muff transistor numbering.. never mind..)  

Could we see some pics of your build..??
(Q2 voltages are way off and Q1 seems dead-shorted..)

I was very confused after looking over several different schematics! Some have Q1 by the output, others show Q4.

[antonis]

Could we also see some pics of solder side..??

P.S.
I presume you do have some kind of isolation between PCB solder side and enclosure..

[Benjamos86]

Could we also see some pics of solder side..??

P.S.
I presume you do have some kind of isolation between PCB solder side and enclosure..

I can get some of the bottom side. Yes board is isolated from enclosure. I do think my issue is on the solder side. I've yet to build on a board with this close of spacing. I'm used to the vintage spacing layout boards. This was a challenge for me for sure

[Mark Hammer]

Some circuits pretty much demand a PCB and layout for any hope of succeeding.  But the Big Muff, of pretty much all issues except the op-amp version, is one of those things that can be just as easy and speedy to make on perfboard as any other method.  I find such discrete transistor circuits translate into left-to-right perfing quite easily.  Same goes for pretty much all Tonebender derivatives.

That's not to admonish the OP, or slag PCBs from any source.  But the advantages of a commercial PCB vary with the context and circuit. 

[Benjamos86]

So it ended up being something on the board solder side. Not exactly sure where the issue was, but I populated a new board and now it's working great!

Lesson learned: SLOW DOWN, take your time on your builds!

Thanks guys