Tonepad La Rata-Rat distortion Low Output problem

[ytarikkocaturk]

Hello everyone. I have just completed a tonepad la rata built. Circuit actually working however the output volume is extremely low. I have searched in the forum and seen that a few people also faced this problem. However, I still could not find the solution.
I made an audio probe test. But since the circuit working i started to doing test from output.  When i followed the circuit from output, saw that there is a loud and distorted sound on the " G" pin of the 2N5458. So i thought the transistor was broken but when i changed it with a new one ( i also tried a substitute transistor), but the result did not change still I can get the loud sound on "G" pin and lost it when I try "S" pin. So the problem is not the transistor. Only substitution i have made is using a 33 pF transistor instead a 30pF. I am explaining all these stuff with also on the pictures in the attachment. Also posting the voltage values.

I use a 9v volt battery but please note that voltage value of the battery was 8.11 V measured with multimeter.

LM308N:
P1: 7.47V
p2: 4.03V
p3: 3.64V
p4: 0V
p5: 0V
p6: 4.03V
p7: 8.10 V
p8: 4.10

2N5458
G: 0V
S: 0V
D: 8.09V

[willienillie]

The layout is for a DSG-pinout JFET, are you sure your 2N5458 conforms to that?  They can vary between manufacturers, even of the same type.  Also, there are plenty of fakes around these days, where did you buy yours?  Unrelated, but I'm curious why the Volume pot is hooked up backwards, and also there's a good chance it has been damaged because you soldered in the little rivet holes.

[ytarikkocaturk]

Thank you for your answer.First I connected the pots with wires. However, after some amount of time spent on troubleshooting, I thought the problem might be the pot connections so i soldered them directly. Basically, I solder one of them reversely because there was a chance to make a bridge connection. I will consider that if the pot is damaged or not if I solve the problem and finish the project. But, at this point since I found out that there is no an considerable signal after the transistor, the volume pot already has no function at this moment.  And, about jfets, I am not really an expert on electronic components. I have ordered the ones that i have from aliexpress. But, I also tried 2n5457 and the result did not change. However, if you have any suggestions about testing them if they are properly usable in this project, I would like to hear it. Thanks again.

[willienillie]

I forgot to say welcome, first of all.  Second, let's ignore the volume pot for now, clearly you have a problem around your JFET, the 0v readings tell us that.  Can you post a picture of the back of your board?

[antonis]

Check for proper Source resistor value (10k)..

[Fancy Lime]

The layout is for a DSG-pinout JFET, are you sure your 2N5458 conforms to that?  They can vary between manufacturers, even of the same type.  Also, there are plenty of fakes around these days, where did you buy yours?  Unrelated, but I'm curious why the Volume pot is hooked up backwards, and also there's a good chance it has been damaged because you soldered in the little rivet holes.

+1 to that. Whenever I had this problem, huge volume drop after a JFET, it turned out to be that I got the pinout wrong. The problem with ordering from Aliexpress and the likes is that there are plenty of fake parts going around, especially for old components that are more popular with DIYers than with large consumer electronics manufacturers. So there is a chance that your "2N5458" JFETs are not really 2N5458 and possibly not even JFETs. They may be real, though. The problem is that it is hard to know. Do you have a breadboard and can try to build just the JFET buffer on the breadboard? That may help pinning down the problem.

Also +1 to what Antonis said. Check if the resistor is the right one and also check it with a DMM. Sometimes resistors have internal shorts due to having suffered too much power at some point in their life. That is pretty rare especially with anything above 1k but I don't know where your resistors come from, so it may be worth testing.

Andy

[ytarikkocaturk]

Thank you all for your replies. I have checked 10k resistor and it works properly. About the transistor, i can not be sure they are real or fake. I am also sending the back of the board for willienillie. If there is any other experience to share I would like to hear it. As a last resort i will order new jfets and a new ic from a local supplier. If it doesnt work again  I think i am going to build a new circuit.

[antonis]