Big Muff Pi (GGG Green Russian Specs) help, please

[Russjp1985]

Hello,

Wondering if anyone can lay in on feedback on an issue I am having with my recent build.  The tone sounds great, but the volume is considerably lower than it should be.  Anything below the volume on 7 is totally unusable.  Not sure what the issue is, but the readings for Q4 are considerably off.  Checked all the traces and component values around it, but can't seem to find anything wrong with the build.  Here's my current readings:


Power Supply: 14.45

Q1:
C= 7.0
B= 1.3
E= 0.2

Q2:
C= 7.1
B= 1.3
E= 0.24

Q3:
C= 7.0
B= 1.3
E= 0.3

Q4:
C= 13.6
B= 2.9
E= 1.6

Obviously, these results are good deal off from the readings listed, but based on the volts the power supply is putting out it seems like the results are correct with the exception of the collector for Q4.  Any idea on why just this particular value is so high? The only component between this and the positive end of the power supply is the one 10K resistor, so I've checked around there a good amount, and find anything wrong with this connection.  Anyone know of any other issues that might be causing this volume drop / strange Q4 value?  Much appreciation.

[mth5044]

Someone recently had the same (or similar) problem a little bit ago. Chec that R23 is 2k WITH A MULTIMETER and not 10k ohms as the colors are very similar, if not the same.

[petemoore]

   
   Gain stage
  Gain / Clipping stage
  Gain / Clipping stage
  tone control [passive]
  Gain / recovery stage

[brett]

Hi
The collector voltage on Q4 is way too high. Q4 is almost in cut off mode.

Using this calculator http://www.daycounter.com/Calculators/Transistor-Bias/NPN-Transistor-Bias-Calculator.phtml
I get a collector volatge of around 5 volts (Rb1 = 390k, Rb2=100k, Rc=10k, Re=2.2k).

In your case, Rc might be 1k (or 2k ?).  Less likely is that Rb2 is too low (10k instead of 100k?).

[Russjp1985]

Thanks everyone for the information.  These all seem to back up my initial thoughts as well, so I'm feeling more optimistic about checking the same things over and over again :-)  I checked with a multimeter on R21, R23, and R24 about a dozen times and everything seems spot on as far as the resistance goes.  After work today I'll try it with a fresh battery in my multimeter ... maybe my readings are coming back inaccurately.