Hi I've just built a tube screamer with the schemes and pcb's on generalguitargadgets and the problem is, when i use the original 4558 sent me by small bear, it doesn't work at all, but as i plug an equivalent IC bought at a local store it works, it increases a lot the volume but gives not much distortion! i don't know what to do, the pots are not much influencing the sound but the wiring is correct, the components are correct... so? Here are the voltages at the IC's:
JRC 4558D:
pin 1: 1,87
pin 2: 1,49
pin 3: 3,69
pin 4: 0
pin 5: 2,03
pin 6: 1,28
pin 7: 1,17
pin 8: 9,18
Battery was 9,18 volts
ST 4558:
pin 1: 4,80
pin 2: 4,75
pin 3: 4,46
pin 4: 0
pin 5: 4,77
pin 6: 4,72
pin 7: 4,54
pin 8: 9,11
Battery was 9,11 volts
HELP MEEEE !!!!
I'm not familiar with the GGG board, but pin 8 should be the voltage of your battery (which it is), pin 4 should be ground (ZERO which it is), pin 3 and 5 should be about half of your battery voltage. (Which it is on the ST4558 but not on RC4558).
In any case both op amps should work and therefore there is a mistake on either the wiring or the board. It could be a bad solder joint or solder bridge.
Referencing this picture:
(http://www.diystompboxes.com/pedals/ampins.GIF)
and this by R.G.:
QuoteFor an opamp to be working as a linear amplfier, both the inverting and noninverting inputs and the output pin must be within a few millivolts of the voltage on the noninverting input.
OK, so the ST4558 looked more correct. Perhaps the JRC was in backwards???
In any case there is some sort of wiring mistake. Does the drive pot work?
How about the other pots???
Well i understood... i've plugged the 220/9 volts adaptor in the circuit but i didn't know that the output was about 14 volts! so i've fried the ST too!
Now the voltages are similar to the JRC.... :roll:
So, i'll have to buy the IC again, and pay more attenction...
But may be there any component that has broke? I mean, the transistors
seem to work, what about the diodes?
The pots werent very influencing the sound, just adding some noise... but i think becouse the were flying and not connected to ground.
Thank you aron!
I think something else is going on. The chip should be able to handle 14 volts no problem.
Really? It smelled strange after, but i'll check better
ty again.
Your adaptor is DC right?
yea, i've also checked the on board components, all placed ok, no shorts on the pcb and correct wiring...
http://focus.ti.com/lit/ds/symlink/rc4558.pdf
Texas Instruments datasheet: Vmax = 18 volts
http://www.st.com/stonline/books/pdf/docs/2181.pdf
STMicroelectronics datasheet: Vmax = 22 volts
mmmm :roll: :roll: :roll: may be a combination of overvolted transistors ?
I've ordered a few 4558 and 4559 form texas instruments, let's see.