Problem with very low volume

[SuperGeo]

hello guys

i've done a GT2 so, now i was testing and the sound was very very low... well then I saw that the volume pot was not working, I turned it and nothing happens... I think that the only pot that is working is the Drive, because I see no changes in the sound when turning the High and low pots... maybe because the sound is low...

i was not able to find the 3 position switch here, so I connected all 1 and 4 wires to get the Hot wired, off axis california sound

another thing, it is noisy, there's HUMMMMMM in there :/

sometimes when i put my fingers in the copper side on the board, the sound gets more louder... I checked the components, the wiring and the board and it looked Ok

so, i don't know what is happening  :cry:

[BIGROCKSHOW]

anyway you could take pics or scan the board?

[R.G.]

The simplest explanation for what you describe is that signal ground is not connected to the volume pot, and is possible not connected other places, either.

I think you have a wiring problem.

Is this your first build?

[SuperGeo]

sorry I can't take pictures of my board because I don't have a digital cam here...

I fixed that problem about the volume pot... it was an path that's didn't appear in the PCB maybe there wasn't toner enough

well, but now i have more 2 problems :/

first the 'high' pot, when is totally down, there's no sound... same thing with the drive pot.

second is that if i put every pot totally up, the overall volume is still low then the bypassed!


R.G well, I built a Mxr, an orange squeezer and a mixer, before this GT2

[R.G.]

I fixed that problem about the volume pot... it was an path that's didn't appear in the PCB maybe there wasn't toner enough

Great! Did that help the hum, as well?

first the 'high' pot, when is totally down, there's no sound... same thing with the drive pot.

The high pot thing sounds like a short in or around a capacitor. Drive pot may or may not be supposed to act that way; I'm not familiar with the schematic.

R.G well, I built a Mxr, an orange squeezer and a mixer, before this GT2

No problem. I was just trying to gauge your skill level. We get all levels.
[/quote]

[SuperGeo]

Great! Did that help the hum, as well?

yes

well, now my only problem is about the volume... it still low :/ I tried to change the OpAmps (i'm using4558 and tl072 in mine) but it had no effect

[RDV]

well, now my only problem is about the volume... it still low :/ I tried to change the OpAmps (i'm using4558 and tl072 in mine) but it had no effect

I believe that TLC2262 are the only OA for this circuit. Use the search function of this forum and put in GT2 and you can look at a bunch of threads about this circuit.

RDV

[SuperGeo]

hey, I was checking the board, and I saw that i changed two resistors, an 2k2 with 22k


well, I put they in the correct places and now the sound came up higher! \o/    now all the pots are working as it should but the volume is still low than the bypassed :/

i checked all the capacitors and they are all correct

any ideas? ^^ bye

[SuperGeo]

I recorded an mp3 file

first part, bypassed
then, with pedal ON

http://cifraclub.terra.com.br/palcomp3/mp3/2269_1091134163.mp3

[SuperGeo]

hey, i forgot to say this

6k2 isn't a commercial value, i don't know, but here in my city is
so i'm using a 6k8 resistor, there's any problem by using that? or should I try to combinate other values to get there?

[SuperGeo]

and I used an BC549B in place of the 2N5088... i think that the problem is about the transistor...  

there's any another substitute that can i try here?

I measured the voltage of ICs transistors and it looks Ok

[SuperGeo]

values:

+V 11.17

ICs (all 4558)

IC1

1 5.9
2 6.0
3 3.02
4 0.00
5 3.04
6 6.01
7 5.99
8 11.19

IC2

1 5.56
2 6.08
3 4.92
4 0.00
5 5.54
6 5.92
7 5.59
8 11.18

IC3

1 5.60
2 5.59
3 5.29
4 0.00
5 5.21
6 5.58
7 5.58
8 11.15

IC4

1 5.57
2 5.58
3 5.56
4 0.00
5 5.57
6 5.58
7 5.51
8 11.18

Transistor (2N3904)

c 11.19
b 5.58
e 4.94

[petemoore]

Pins 3 and 5 of oa 1
 also pin 3 of OA 2..
 These voltages look low, I just reread biasing at GEO, the + and - inputs should be within 10mv of the output of that Opamp...if memory serves [Read that section for more reliable info]
 I like when all the + and - inputs, and the output of an OA is close to 1/2v...they just seem to work fine that way...please correct me if I'm missing something, this is just IMExperience typing...

[SuperGeo]

hey guys

i used a socket for the  transistors... well i  was swapping 2N3904 and BC459B and nothing changes do i think the problem is not in there

i've checked all the values of capacitors and resistors many and many times, and everything looks in the right place...

I checked the board and all the 'paths' twice and i've didn't found any missing paths or shorts

I swapped IC's, they are working so the problem is not in there


So i now think that there are a bad Resistor or a bad capacitor in the board... but how can I know if it is working? should I desolder and test every one? it sux, but i'll try this if there are no other possibilities...

Well, i'm using a DPDT rele, but the all the wiring looks correct.

well, thanks for your time   :lol:

[SuperGeo]

i got an capacitor for the 560pf but in there is write

"TRW
560M
X5F"

is that 560pf?