Dr. boogey problem Debugging

[Hupla]

1.What does it do, not do, and sound like? Its not high gain enough. Sounds like it is overdriving

2.Name of the circuit =Dr. Boogey

3.Source of the circuit (URL of schematic or project) = Using gaussmarkovs layout

4.Any modifications to the circuit? Y or N Y

5.Any parts substitutions? If yes, list them.
1. C5 56pf instead of 20pf (it was all I have. Im guessing this may effect the gain as its near the gain pot, so this may be the problem.
2.C10 4.7nf instead of 6.8nf
3.C13 33nf instead of 30nf
4.C15 4.7nf instead of 5nf
5.R1 2.2M instead of 2M
6.R4 690K made up of two resistors in series instead of 680K


6.Positive ground to negative ground conversion? Y or N N

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =
Voltage at the circuit board end of the black battery lead =
not using a battery

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
D = 4.42v
S = .37v
G = 0v

Q2
D= 4.4v
S= .38v
G= 0v

Q3
D= 4.4v
S= 3.19v
G= 3.19v

Q4
D=4.5v
S= .38v
G= 0v

Q5
D= 9.4v
S= 4.7v
G= 4.5v

Q3 looks like the problem to me but Im not sure what could be wrong. Its letting sound through so I don't think its broken.
The trim pot for Q3 is really noisey when I move it and it shoots from 6v to 9v much quicker then the other trim pots but Its manageable.

Anyone any ideas?

[PRR]

Parts-substitutions may be OK (you do not say -what- two resistors were used for R4).

> not using a battery

Good to know "battery voltage" even when "battery" is a wall-wart or solar-cell or whatever you are using.

> Its letting sound through so I don't think its broken.

A wire "lets sound through" but makes a lousy amplifier.

Without a link to the actual schematic, I'm guessing Q3 is biased to be a "wire".

Why is Q3 Gate lead up at 3V, when the others (except Q5 which is likely a buffer) are at 0V? Way it is supposed to be? Mis-wire? Solder-bridge? Cap from Q2 to Q3 shorted?

[jkokura]

What modifications are made? You said yes to the question but only list substitutions... did you mean that your modifications are the substitutions? The only one that's going to make a difference is the first one you mentioned. I don't know what it would do, but it could be the source of the problem.

Also, Have you looked up to see what the Q readings 'should' be? I haven't built mine yet, but I'm sure if you searched you'd be able to compare your numbers to others results.

And giving us the power supply numbers helps also.

Jacob

[Hupla]

Parts-substitutions may be OK (you do not say -what- two resistors were used for R4).

> not using a battery

Good to know "battery voltage" even when "battery" is a wall-wart or solar-cell or whatever you are using.

> Its letting sound through so I don't think its broken.

A wire "lets sound through" but makes a lousy amplifier.

Without a link to the actual schematic, I'm guessing Q3 is biased to be a "wire".

Why is Q3 Gate lead up at 3V, when the others (except Q5 which is likely a buffer) are at 0V? Way it is supposed to be? Mis-wire? Solder-bridge? Cap from Q2 to Q3 shorted?

What modifications are made? You said yes to the question but only list substitutions... did you mean that your modifications are the substitutions? The only one that's going to make a difference is the first one you mentioned. I don't know what it would do, but it could be the source of the problem.

Also, Have you looked up to see what the Q readings 'should' be? I haven't built mine yet, but I'm sure if you searched you'd be able to compare your numbers to others results.

And giving us the power supply numbers helps also.

Jacob

Thanks guys. The problem was at Q3. There was a solder bridge. Everything is fine now Except it sounds a bit different to other recordings i have heard but that's to be expected.

Thanks for all your help.