Problem: TubeScreamer from generalguitargadgets.

[served]

Hello.

I just built TS808 from generalguitargadgets, it sound good. But Drive knob seems to be pretty useless.
Has any one experienced the same problem?
If i turn the drive knob to zero then i still get sound from my amp, its allmost clean but not much different from the Drive maxed sound.
Any suggestions?

Other thing. If i play with LEDs clipping, should they flash a bit? I think there is something wrong with the thing, but i cant find any bad parts...
And this really anoying thing is that it pops. It shouldnot! If i switch it on i hear a pretty loud pop! Any suggestions?


Some voltages:
Q1
9,1V
2,6V
3V

Q2
9,1V
2,3V
2,45V

IC (JRC 4558D)
Left, from up to down
4,5V
5V
4,45V
0

right, from down to up
4,5V
6,6V
4,5V
9V

[fuzzo]

I think it's caused by the diodes. They have a higher treshold compared to regular 1N4148 or 1N914, so the dirstortion comes later. I've done the same test few day ago in a overdrive circuit. I changed 1N4148 diodes in feedback with 2 red LED 3mm and the sound stays clean lounger, the ovedrive started to come when the pot. at max (and even in that position that didn't have the same ovedrive level than with 1N4148)

Other thing. If i play with LEDs clipping, should they flash a bit

not necessary. If the voltage coming in diodes is too low to flash, they don't flash (but the signal pass through).

If you want to keep the led clipping, maybe increase the gain in changing the 4K7 Resistor (the one with the 47n that goes to the ground (or Vr) attached to the diodes) for a 1K.

Changing that resitor will change also the frequency response, so I'll have to change the 47n cap to conserve the frequency response of the circuit (220n I think) .

this page can help you to understand :

http://www.muzique.com/lab/fatt.htm

[petemoore]

Some voltages:
Q1
9,1V  Assuming this is the collector, a conservative estimate of battery voltage shown.
2,6V      ...Base ?...
3V   ...Emitter ?
 If so, the base should be above the emitter by 1 B/E diode drop voltage [.6v or so
Q2
9,1V
2,3V
2,45V
 Same thing here..Emitter above base and the transistor won't pass signal.

IC (JRC 4558D)
Left, from up to down
4,5V
5V
4,45V
0

right, from down to up
4,5V
6,6V
4,5V9V
 I'm not sure about the 6.6v on OA pin 6, the voltages look like it should work though.
 The pin designations  would be for Q1, Q2, C/B/E, and OA1 pins 1,2,3,4,5,6,7,8, and are all seen as %ages of battery voltage, in this case it's safe to assum the battery is >9v though.

[R.G.]

I just built TS808 from generalguitargadgets, it sound good. But Drive knob seems to be pretty useless.
Has any one experienced the same problem?
If i turn the drive knob to zero then i still get sound from my amp, its allmost clean but not much different from the Drive maxed sound.
Any suggestions?

The drive knob cannot reduce the sound to zero. It will be almost clean. The sound not being much different from max drive is a problem. It suggests incorrect wiring of the drive pot or possibly the wrong value of drive pot.

If i play with LEDs clipping, should they flash a bit?

Not necessarily. LED brightness is proportional to the current through them, and the signal currents through these are quite small when used as in the tube screamer circuit.

I think there is something wrong with the thing, but i cant find any bad parts...

It is a big mistake to think that the only thing wrong with a newly constructed pedal is bad parts. Experience with literally thousands of beginners making pedals has shown that the most common faults are (1) wrong part inserted, or part inserted with the pinouts wrong (2) bad soldering (3) incorrect wiring. Finding a truly faulty new part is really quite rare.

And this really anoying thing is that it pops. It shouldnot! If i switch it on i hear a pretty loud pop! Any suggestions?

That's likely to be an electrolytic capacitor at the input or output which is inserted backwards. Or possibly a wiring problem. Given the issues with the drive pot, I'd guess it may be wiring.

[served]

Ok. Ill digg some more.

[served]

Update.

Drive knob was not working, because the pot was reverse LOG so i just connected it backwards now and its working.
But still. LED clipping i get clean sound. And the POP still comes when switching.

Is it a problem: 51pf(C4) is 47pf because i didnt have 51
All the other components are checked and they were correct, exept Q1 and Q2 (2N3904) should i un solder them and check if they are the bad guys?

[R.G.]

But still. LED clipping i get clean sound. And the POP still comes when switching.

Use your meter and check the DC levels on your input and output jacks.

[BAARON]

LEDs will sound very clean in comparison to silicon diodes.  Silicon diodes clip at ~0.6 volts, while many LEDs don't clip until ~1.5-1.8v, so there's a lot less clipping going on, and at lower gain levels there probably won't be Any clipping going on.

The 47pF vs 51pF cap won't be a noticeable difference.

[served]

input and output voltages? I dont seem to get anything.
I changed the opamp, now its in socket. The old one is also working. I checked the el caps and Diodes. Nothing seems to be wrong. but still, this stupid POP.

[R.G.]

input and output voltages? I dont seem to get anything.
I changed the opamp, now its in socket. The old one is also working. I checked the el caps and Diodes. Nothing seems to be wrong. but still, this stupid POP.

1. What kind of meter are you using to check voltages?
2. Can you remeasure the voltages, and also include the voltages on the pads that the wires from the jacks and controls go to on the board? Maybe give a link to the layout/schematic so we can follow what you're doing.

[served]

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=82&Itemid=26

This is the project.

[R.G.]

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=82&Itemid=26
This is the project.

Cool.
1. What kind of meter are you using to check voltages?
2. Can you remeasure the voltages, and also include the voltages on the pads that the wires from the jacks and controls go to on the board?

[served]

ill add the data next week. I have been away some time. Sorry.

[served]

Voltages.

Line Output signal voltage is 2.8V

Power supply voltage is 9,1V
I    0V
D1 4.68V
C2 4,8V
D3 4,5V
9,1V
C1 4,8V
C3 3,3V
V1 4,5V
T1 4,5V
T3 4,5V
V3 4,15V
L  3V
V2 4,3V
T2 4,5V
O 2,8V

Q1
C: 9,1V
B: 2,6V
E:  2,9V

Q2
C 9,1V
B 2,5V
E 2,8V

[R.G.]

Great, thanks.
What kind of meter are you using to measure voltages? This is important because meters vary in how much they disturb the circuit being measured.

Line Output signal voltage is 2.8V

This is why your pedal pops.  That voltage must be 0.0V for switching to be quiet.

It is likely that your output capacitor is shorted or inserted backwards. This would be C11. Measure voltages on both sides of C11. If it's the same on both sides, there is a short. If it's different, C11 is likely inserted backwards. Also check the polarity (+ or -) of the voltage on both sides of C11. The side with the + symbol must be a higher DC voltage than the - side.

Q1
C: 9,1V
B: 2,6V
E:  2,9V

Q2
C 9,1V
B 2,5V
E 2,8V

These notes make me think you're using a low-impedance measuring meter. That's OK, but it has to be taken into account when considering the voltages. These measurements are clearly wrong if you're using a high impedance meter. But if they are the actual readings, no sound would go through at all. Since it does, the transistors must be working, and the measurements are suspect; the easiest way that would produce that is a low impedance meter.

[served]

Im using Digital Multimeter DVM830L in DCV 20 mode.

[served]

How could i ever thank you!
Thank you very much! That was it, cap was dead... I put another one in and now it works like a real thing!
Many thanks to all of you.

A.

[R.G.]

How could i ever thank you!
Thank you very much! That was it, cap was dead... I put another one in and now it works like a real think!
Many thanks to all of you.

You're welcome. Congratulations on your new build!