Tried to perfboard a Barber Silver LTD... some problems here!

[lazerphea]

Hi everyone,
I tried to perfboard the Barber Silver LTD, and after a week trying to find out by myself what's wrong with my build, I kindly ask to you guys if you could help: the circuit does exactly what is cited in the "DEBUGGING - What to do when it doesn't work" thread as an example of malfunction, that is "it makes a harsh, distorted sound only when I strum hard on the strings at full volume".

Here's all the data I could gather; thanks to everyone willing to help me.


Schematic = http=//www.barberelectronics.com/Barber_Electronics_DIY.html

Perfboard layout (mine):



Battery output = 8.76

The voltage divider is ok, it outputs 4.45V;


IC (4558):
P1 = 7.94
P2 = 7.55
P3 = 0.01
P4 = 0.01
P5 = 3.96
P6 = 4.44
P7 = 5.35
P8 = 8.76

(diodes are all 1N4148, numbering refers  to the perfboard layout)

D1:
A = 7.70
K = 7.51

D2:
A = 7.94
K = 7.66

D3:
A = 7.54
K = 7.28

D4:
A = 7.29
K = 7.94



Output electrolytic cap (4.7uf):
positive = 5.24
negative = 0.1

Presence trimmer:
left pin = 4.32
wiper = 4.32

Mid trimmer:
left pin = 4.38
wiper = 4.54

Bass trimmer:
left pin = 4.55
wiper = 5.28

Moreover, all the pots seem to work, i.e. if I generate some noise touching the tip of the input cable, if I turn down the volume it turns down, if I move the drive pot I can hear a difference in the intesity of the noise, and so on.
I hope I gave you all the information needed.
Cheers,
Paolo

[GibsonGM]

Try audio probing the circuit, see where the issue is.  Sounds like a poor solder joint, maybe a solder bridge.  It's best if you can track it down to a section.   Search for "audio probe" on here if you don't know how to make one....
I did spot this offhand, though:

1) Pin 3 should have the 4.5 Vref voltage on it...I'm not seeing it in your list there, maybe the connection was missed, major if so....
2)  Are all your diodes oriented correctly?

[lazerphea]

Try audio probing the circuit, see where the issue is.  Sounds like a poor solder joint, maybe a solder bridge.  It's best if you can track it down to a section.   Search for "audio probe" on here if you don't know how to make one....
I did spot this offhand, though:

1) Pin 3 should have the 4.5 Vref voltage on it...I'm not seeing it in your list there, maybe the connection was missed, major if so....
2)  Are all your diodes oriented correctly?

Hello Mike, thanks for your suggestions; tonight I'll try to audio probe the circuit, in the meantime I checked the voltage at pin 3, and without the guitar connected to the input it reads 2.45V... not the 4.5V... I don't know what to do about it :\
The diodes are all oriented correctly; maybe I shoud just try to rebuild it!
Thanks again!
Paolo