DIY: Green Russian Big Muff problem

[khm9]

Hi,

After successfully building Rams head vero, I didn't like the sound at all, it just sounded processed, boring and harsh.

So I transformed it in to a Green Russian.
Link: http://tagboardeffects.blogspot.com/2012/06/ehx-green-russian-big-muff.html

Anyway, the problem is volume, it is INSANELY low on max, like completely low with my 15w amp turned up to half. Bypassed sound, works and is 100 times louder compared to the pedal on, vol max.

I replaced every part that needed to be replaced (resistors, caps, moved diodes in correct place) except the 3 caps, those little ones 500p. I left 470p from rams head, I didn't think it would make a difference.

Pots are from the rams head build, 100k log, where as on green russian pots should be 100k lin.
Could this be the problem, if so why?

Transistors are 2N5089.

I measured the voltages and they appear okay to me, emitters on Q2, Q3, Q3 look suspicious though...

Q1 (upper left corner)
E: 1.21
B: 1.78
C: 3.61

Q2 (down left corner)
E: 0.09
B: 0,60
C: 3.74

Q3 (upper right corner)
E: 0.03
B: 0.61
C: 3.67

Q4 (down right corner)
E: 0.04
B: 0.61
C: 3.72

What do you think the problem might be?

Could it be that those little 470p are making this problem?
Or can a short make a problem, not that I saw one, but is it possible for circuit to be shorted and still work on insanely low vol and show voltages?
Or even those pots? which I suspect the most.

Thank you.

P.S. I kept the wires from pots, switches, jacks soldered to the PCB during the modification, so wiring is most likely not a problem.

[chuckd666]

Upload some pics of the board I reckon.

[Elijah-Baley]

Something like that happend to me, too. There was a pair of resistor with wrong value.
Check the orientation of the transistor, but more than else check every single part you have replaced.
If you can't solve, try to turn back to the ram's head until you find out the mistake.

The 500-470pf caps don't change the volume, but those change a bit the eq. If you want see how works some parts you could use socket pins for the critical parts of the several Big Muff schematics.

[EBK]

...moved diodes in correct place

Curious about this statement.

[khm9]

Upload some pics of the board I reckon.

Alright

Something like that happend to me, too. There was a pair of resistor with wrong value.
Check the orientation of the transistor, but more than else check every single part you have replaced.
If you can't solve, try to turn back to the ram's head until you find out the mistake.

The 500-470pf caps don't change the volume, but those change a bit the eq. If you want see how works some parts you could use socket pins for the critical parts of the several Big Muff schematics.

I'll double check all the resistors... Transistor orientation is good, I think voltages are okay as well, need confirmation on that from someone.

Nobody told me if pots are the problem? I kept the pots from rams head (100k log) but according to the green russian's vero I should've put 100k lin?

...moved diodes in correct place

Curious about this statement.

Position of all 4 diodes is not the same on rams head and green russian's vero.

[EBK]

Position of all 4 diodes is not the same on rams head and green russian's vero.

But the vero layouts are the same?  Did you use the linked layout?  If not, I wouldn't mind comparing them.  I really suspect this will be a second pair of eyes fix....

[EBK]

The pots are not a problem.

[khm9]

Position of all 4 diodes is not the same on rams head and green russian's vero.

But the vero layouts are the same?  Did you use the linked layout?  If not, I wouldn't mind comparing them.  I really suspect this will be a second pair of eyes fix....

Side by side comparison:

[EBK]

Did you also move the corresponding 100nF cap?

[khm9]

Did you also move the corresponding 100nF cap?

All 100n caps are moved to correct positions.

[duck_arse]

there seems to be, from looking the photo, a cap missing between "Volume 3" and the C of the top-left transistor. is it there but obscured?

[khm9]

there seems to be, from looking the photo, a cap missing between "Volume 3" and the C of the top-left transistor. is it there but obscured?

Good eyes!!

Even though I checked 20 times to see if something is missing I missed that...
I will install it and let you know in the next hour.

Thank you!! 

[khm9]

Hi,

Fixed it! thanks! It works.
But now, I have 2 other problems...

1. Signal drops and rises a bit in volume every 2 secs or so, especially in low E, when all strings played together really noticeable. Inconsistent signal.

2. Hum... I didn't have this problem with rams head, anyway the hum sounds like wind sound caught on camera, like a pedal being connected to a really bad power supply (I ran the pedal with 9V battery).
The hum is sensitive to the sustain pot.
Same amount of hum is also present with the guitar volume pot off.
I also noticed odd sounds when tapping the wires that come out of the board.

Any ideas?

[EBK]

Possible broken trace (phenolic resin boards do not like soldering rework).  Just a wild guess though.

[khm9]

I found out that input wire was making weird noises, so I replaced it, nothing is fixed. Odd sounds still come out when input wire is touched, tapped

[EBK]

Does the solder joint move if you wiggle that wire?

[khm9]

Does the solder joint move if you wiggle that wire?

Okay. Input wire is okay, input wire was touching this one cap while tapping it. When I tap the cap (left corner above 100R resistor, sound gets inconsistent and cuts) so I think it might be a bad cap. I will put a new one

[EBK]

The electrolytic cap?  I believe those shouldn't (can't?) be microphonic (written with complete deference to someone who wants to say otherwise).  Check to see if the copper under it has lifted. 

[jimilee]

Make sure the transistors aren't loose and causing a bad connection. Use a magnifier of some sort to check your soldering and small hairs. Sometimes a joint looks good until it's magnified, then you can see a lead just sitting there, happens to me when I use vero. Check all the usual shorting places, wiring on enclosure, backs of pots, vero touching enclosure, etc...


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[antonis]

Make sure the transistors aren't loose and causing a bad connection.

What he said...!!!