Messages

Thank you for your reply drolo.
Yes, I think there's a problem on the Vb too. If you consider the picture I've attached , I can't understand why the voltage divider made by r21 and r22 doesn't split the supply in half, but I have a voltage on the input of tl071 very close to supply.

Hi guys,
I'm trying to build a bloviator V1 but I've some problems with Ic's pins' voltages.
First of all, I'm using a regulable power supply setted in 9v but I can read 11v on the circuit supply, is it normal?
I've used a sound probe to find the problem and I've seen the output of the first amp (IC1A pin1) is distorted, and after R5 there is a degradation of the sound, hence I've no sound on the output of the second amp stage (IC2A pin1).
With the multimeter I've read the voltages on the pins:
After the first stage (a voltage follower) the output is double than the input.
The voltage reference Vb is close to 10v and I've seen that the voltage divider (r22 and r21) doesn't split the voltage in half, so I have 10v on the output of TL071. Why I have this? what do you think?

I hope I've been clear and somebody will be willing to reply

Ok, thank you very much! 

Hi, which equivalent can I use for 1n695 diodes and 2n404a transistor?

Ok, I fixed it, thank you very much for your help Brian! Pin 2 and 6 went to 0 V because there was a tiny tiny tiny drop of solder between the pin 10 of TL04 and ground track. I've been so stupid because that was a problem that I could see from the schematic, infact pin 6 of TL071 gives the voltage reference Vb, and it cannot be at 0V 

Your supply voltage is quite low at 7.8v. Are you using a regulated 9v supply or fresh battery? If so, something is sinking your voltage...perhaps D1 is faulty.

As far as the tracks, have you tried a continuity tester to be sure? Specifically, I would look at making sure there is no continuity between the R4 pads and the ground plane, plus C3 and its adjacent tracks.

Thank you for reply, but unfortunately it doesn't work yet. I changed D1, controlled that there's no continuity between the r4 pads and ground and C3 and its adjacent tracks, the battery was fresh but I used a regulated 9v supply anyway, and with the power supply came out a 100 Hz signal. The voltages on the pins are rights? If not, can I know the voltages they should have?

Ps. With the battery, the voltage on 9v pin is 8.34 and the voltage drop on the diode is 0.74V. I think it's fully conducting, or not?

Hi everyone,
I've just built a Bloviator (etching the pcb) and it doesn't work. To find the problem I connected the output wire of a test rig on every components following the signal path from IN to OUT and on the output of the first input stage (Pin 1 of tl072) the sound breaks down, so I think there is the problem. The conductive tracks and components values are ok.
Here are the voltages on the Ics' pins

TL072
1 - 1.39
2 - 1.39
3 - 0.88
4;5 = 0
6 - 6.08
7 - 7.17
8 - 7.83

TL074
1 - 1.39
2 - 1.39
3 - 0.91
4 - 7.79
5 - 3.48
6 - 3.52
7 - 2.15
8 - 7.03
9 - 2.10
10;11;12 = 0
13 - 6.87
14 - 7

TL071
1,2,4,5,6,8 = 0
3 - 3.87
7 - 7.8

Here are the photos of top and back of pcb and a little video to explain my problem better.

http://it.tinypic.com/r/20pu70o/5