Stripboard problem

[pokus]

Hey there, I designed and built this stripboard a few days ago, but there is no sound. So I was searching for where the tone is stuck and it turned out that opamp1 has no output. There is tone at non-inverting input but none at the output pin.
So I assume there is something wrong in the feedback path or the power supply unit doesn't work the way I want it to.
Any thoughts on what can be the problem?




IC is JRC4558
D3 a 12V zener
Distortion Pot is 250k
and first R after 9V is 47R

Thanks for help!

[FUZZZZzzzz]

I cant see the whole stripboard, but I dont see any power (9v) going to pin 8 of the 4558

[pokus]

You're right, I just add the first stage for clarity. There is a link from the E line to pin8

[EBK]

Do you have a schematic?
Have you measured any voltages?
Can we see a few pics of the build?

[pokus]

The only thing I've measured is that there is about 9v at pin 8. In the schematic the pins 1 and 2 of the pot should go to in+. I also noticed there is sound at out pin of the opamp but very very quiet when the pot is turned to max

[pokus]

Some more measurements:
between 9V in and line a = 9V
between 9V in and line j = 4.6 V
between line e and line a = 0.6 V
between line e and line k (gnd) = 1.4 V
between 9V in and pin 8 = 8.8 V

Shouldn't the bias voltage before the 1M resistor be 4.6 V and not after it?
I can't spot any mistake in the feedback path so I guess it must be a powering problem.

I really could use some help 

[EBK]

I also noticed there is sound at out pin of the opamp but very very quiet when the pot is turned to max

I'm having some difficulty reconciling this problem with what you stated previously.  I thought you said the problem was no sound at all.

Are you saying you have no sound unless the pot is maxed?

[duck_arse]

can you measure the voltage across your 47R resistor please? it looks very much to me as either 4k7 or 47k, not 47R. also please measure the 100k resistors values.

[pokus]

I thought there was no sound but then I increased the volume of my amp and noticed this extremely quiet sound of the input signal on the output pin of the 4558.
The voltage across the 47R is the same as on pin8 (8.8 V)
from one leg to the other of the 100K it says 0.6 V for both
I also checked the color codes of the 47R and 100K, they are correct.

[tonyharker]

Sory but you have made one basic mistake here, the top end of R2 on the diagram should go - if you are using 9v for your supply, to a 4.5v bias point. The +ve input to the op amp needs a bias supply to set the output voltage. It is difficult as your diagram is not the same as the veroboard layout and doesnt show component values.

[pokus]

Sorry this is a very early and confusing diagram the top of R2 is a 4.5 V bias point, at least it should be one. The power supply unit is the same as the RAT ones and it says that the 4.5 V bias point is between the two 100K resistors and that's where the 1M resistor is connected to.
But the measurements don't match to the original RAT diagram.



there's 9 V at the one leg of the 1M and 4.6 V on the other.

[EBK]

there's 9 V at the one leg of the 1M and 4.6 V on the other.

That doesn't seem right...  What's the voltage at pin 3?

[pokus]

also 4.6 V on the non-inverting input pin

[thermionix]

The voltage across the 47R is the same as on pin8 (8.8 V)

You're dropping 8.8V through that resistor?

Duck was on to something.  I think maybe you have yellow, violet, brown, gold.  Is that right?  That's a 470R at 5% tolerance.  You might be applying 5-band math to a 4-band resistor (4, 7, one 0, x0.1 = 47).  If your third band is red instead of brown, 4.7K.  If it's orange, 47K.

[antonis]

The voltage across the 47R is the same as on pin8 (8.8 V)

You're dropping 8.8V through that resistor?

I think he means that there is a 200mV drop (9V -> 8.8V)..

@pokus: Can't see the reason for reverse power protection with a Zener instead of an ordinary diode..
I can't also see the need for 1k non-inverting bias resistor - unless you want to create a (second pole, added to 13.5kHz created with 47pF & 250k pot) LOW-pass filter (with 1nF cap) of 160KHz cut-off point...!!!!
(you could easily omit it togheter with the cut right next to 1M resistor..)
Your feedback path seems to be OK except of the 1.6kHz High-pass filter created with 100R & 1μF..
(I presume it should work fine with a 1k to 2k2 resistor..)

there's 9 V at the one leg of the 1M and 4.6 V on the other.

In that case, you've placed 1M before 100k/100k voltage dividing point..

[pokus]

Maybe I should have taken a closer look at the 47R resistor like you guys mentioned earlier. I found another one of it and measured 47K ohms  So big thanks for that, I would have been searching for weeks!

Like I expected that isn't my only mistake on my first designed stripboard.
I put in a real 47R and tried again. There now is a extreme amplified sound at out pin, but as I connected the output pot to my amp, it's as loud as my input tone with pot maxed. Everything else just works fine, the pots are doing there job and the LEDs light up. I know diodes and the tone stack are lowering the volume, but when I first breadborded it this circuit was a beast in regard to volume. There's high amplified tone at the legs of the LEDs connected to the 1K but very low amplified tone at both legs of the 100p and 56k. So can it be that there's something wrong with the LEDs although they light up?



@antonis
I'm not that much into diodes so i just took what the power supply schematic told me. Is there any disadvantage of the zener?
I also read that the 1k protects the opamp from input over currents.
The 1.6kHz first order HP filter may seems to be a bit strange, but I really like the result.

[pokus]

sorry just forget about my last post 
everything works fine now, unless i had expected more output and there are still some oscillation problems, but that should be due to the fact that it is still unboxed.
Thanks to all of you for sticking to this problem!!

[antonis]

@antonis
I'm not that much into diodes so i just took what the power supply schematic told me. Is there any disadvantage of the zener?

If you refer to RAT's power supply, it tells about 1A rectifier diode..
(nothing against placing Zener there except of cost..)
BTW, you're lucky 'cause you've placed a Zener of reverse breakdown voltage HIGHER than power supply..
(for Zener voltage lower enough, say 5V6 or lower, you should result in short-time stabilizing to Zener voltage, with Vref the half of it, and finally to a fried Zener, in case of 1/4W device, due to over-current - 47R should let more than 70mA to flow through it..

I also read that the 1k protects the opamp from input over currents.

Indeed but there shouldn't be any case for over-current in your design..

P.S.
Can't see any reason for both LEDs facing the same way...
Do 2 X 100pF in series substitute a 47pF one or is just a boar population error..?

[pokus]

Ok thanks for making that clear. So I guess I'll stick with the zener.
The LEDs produce symmetrical clipping, I just found no way to make that clear in the stripboard programm.
Sorry but I can't figure out what the meaning of "boar population error" is 

[antonis]

The LEDs produce symmetrical clipping, I just found no way to make that clear in the stripboard programm.

Just reverse one of diodes orientation.. 

Sorry but I can't figure out what the meaning of "boar population error" is 

My bad, a missing "d" at the end.. 
(board)