MXR Dynacomp (Tonepad)... Plz help!!!

[igaurav]

Hello good people! This is Gaurav from India. Being just a follower of this site as a guest since past couple of years has helped me successfully make a couple of great pedals but now, I'm in big frustrating problem!
So herez my first post...
I have built tonepad dynacomp PCB and have soldered all the parts but cannt make it sound. Have tried replacing CA3080AE but of no use. Checked rechecked did everything but no success, also checked all the pcb wiring fr any opens / shorts... I also tried taking out the IC and connecting the pin 2/3(I/P) to pin 6(O/P), in that case I'm getting output nice and clean which indicates probably the circuit is right... any ideas what's wrong.
The key voltages are:
             C      B      E
Q1       9.5    1.3   1.2
Q2       7.08  2.8   2.2
Q3       8.5     0      0
Q4       9.0   0      0
Q5       9.4    8.8   8.8

CA 3080AE
in+ 4
in-  4
v+  9.4
out 2.5
bias 6.4

Herez the link for PCB Layout/Schematic : http://www.tonepad.com/getFile.asp?id=9
Plz help out guys!!!
Thanks!

[brett]

Hi
there's a problem biasing Q1.
Vb should be about 3 volts.
If Vb is ok, then there is a problem with Ra, Rb, Rc or the 10k resistor on Q1 emitter.
(Because the base voltage should be 0.7 volts more than the emitter voltage of Q1, and every other transistor, but in your case it isn't.).
cheers

[igaurav]

 
Thanks a lot Brett... yeah you are very right... Vce being comparable to Vb sounds fishy...
In checked the circuit and replaced 56K resistor by 47K but that lead to Vb being lower than Vce. So I concluded that something is feeding voltage to the Emitter and I started cheking for shorts and nailed.... I had a short near the trimpot cracked it and inserted the IC.... and I got the sound... so nice and sweet.... Nailed it Finally... this forum rocks!!!
Thanks a lot guys and Brett I owe you a favour!!!
Cheers!

[igaurav]

One more thing... I always make pedals with an attitude to optimize cost and quality... I made this pedal in 4 USD only, including cabinet components & PCB in 3 days now!
Cheers!
Big Thanks to DIYSTOMPOXES!!!