DC jack wiring problems

[Gledison]

I will post some pictures a.s.a.p
I found something that might help you experts to solve the mistery.
I've got a old battery that is sending 6.5V. With this battery everything is working fine.
I decided to check with a new one and guess what? the same problem as i got with the adapter.
it seems that the problem is on the pcb than?
it seems to me that somehow is not accepting more than 7V, anything higher, it starts to crash!!!
maaaaaaan this thing is getting very interesting!!!
any diagnostic?
cheers

[RobA]

Well, that changes everything. Now you need to check all the standard stuff, voltages, solder bridges, component values, etc.

If it's got op amp gain stages, pay close attention to the parts in the feedback sections. Make sure they are the right values and that they are making contact with the PCB and there are no bridges on the pads.

Probing for audio and seeing where it starts to squeal would help too.

[Gledison]

RobA, i have no audio probe (yet).
i've found the GGG tubescreamer IC voltage specs. Im using the tonepad layout but , here we go:

original voltage (from DC adapter=9,35V
Ic pins
1- 4,7 V (4,5V)  5- 4,7 (4,5V)
2- 4,9 V (4,5V)  6- 4,7 (4,5V)
3- 4,7 V (4,5V)  7- 4,7 (4,5V)
4- 0 V  (0V)       8- 9,35 (9 V)
on brackes are the GGG measurements
It seems to me that the IC is ok.
im using 2 transistors 2N3906 (on tonepad should be 2N3904)
my measurements are:
(in brackets are the measurement for the 2N4401)
Q1 e = 1,36V (2,5V)
     b= 8,72V (3V)
     c= 9,35V (9V)
The same values for Q2 were obtained.
it seems that my emmiters are sending less that it should and the base is quite high!
could be only a differnce from the 2N3906 in comparison with the 2N4401 ?
so, any further help
cheers folks!




thanks mate!

[RobA]

The 2N3904's and 2N4401's are NPN transistors. The 2N3906 are PNP. They aren't interchangeable. The transistors are just being used in an emitter follower, so going from the 2N4401 to the 2N3904 won't make any difference really. Actually, you can use pretty much any NPN BJT here as long as you get the orientation of the pins right. But, you can't use PNP.

[Gledison]

Cooooooooooool! you got it!
damn! when i bought the parts the guy told me that was equivalent! BAs"%£$%%rd!
Well, i will change and i hope will be fine.
thanks a lot for your help!!!
cheers

[Gledison]

Can i use a 78L05 instead of the 2N3904 ?
cheers

[RobA]

Can i use a 78L05 instead of the 2N3904 ?
cheers

Nope. The 78L05 is a 5 volt voltage regulator. It's just in the same package as a transistor. What you need to be looking for is an NPN transistor (not a power transistor though). Some examples are 2N5088, 2N3904, BC547, BC549C, and BC550C. The BC549C and BC550C are nice because they are low noise devices. But, they certainly aren't needed in this circuit. There are lots of others that would work too. The best thing to do is check the spec sheet to make sure that the device you are considering is an NPN transistor. It should say that at the top of the spec sheet for any transistor that is. If you just type the part number into the search at Mouser or the like, they'll almost always have a spec sheet for the part.