the rails of the tda circuit, it have a little damaged...for other hand, i remember that the person that checked the amp for the first time, replaced the tda, and when he was checking with he multimeter (with the power on) he created a spark...maybe the new tda is defective.
the capacitors seems to be ok, but again, i dont know how to check it. I put one side of the meter (red) in the positive and the other on the negative, and for less the a second it gave me the sound of continuity and then give me a lecture, followed by the "1" of open circuit...
the capacitors seems to be ok, but again, i dont know how to check it. I put one side of the meter (red) in the positive and the other on the negative, and for less the a second it gave me the sound of continuity and then give me a lecture, followed by the "1" of open circuit...
SOunds like the power amp is now cured. If the power amp had the noise issue, it would make noise no matter what channel was selected.
The lead channel will naturally have more hiss than the clean, due to the much higher gain. But if it is excessive, even considering that, then you probably have a noisy op amp.
Do this. Select the lead channel so you hear the noise. Now turn the lead channel controls up and down. WHich ones have ANY effect on the noise? Gain control, tone controls, contour control, volume control. WHich ones do and do not make a difference in the sound or its volume? That will help locate the area of the problem.
The lead channel will naturally have more hiss than the clean, due to the much higher gain. But if it is excessive, even considering that, then you probably have a noisy op amp.
Do this. Select the lead channel so you hear the noise. Now turn the lead channel controls up and down. WHich ones have ANY effect on the noise? Gain control, tone controls, contour control, volume control. WHich ones do and do not make a difference in the sound or its volume? That will help locate the area of the problem.
ok I tested all the channels, and the treble knob have a lot to do with the noise overall
1) the clean channel doesn't have a noticeable problem with the noise, until i get it to the top...well, middle actually (gain 7, MasterVol 7, and treble 10)...almost intolerable noise.
2) the crunch channel: doesn't have too much trouble, until i get it to more than 5 in treble (Gain 10, volume and MasterVol not so high actually more or less than 5)...almost intolerable.
3) OD1 doesn't have too much noise, even gain and volume doesn't have much to do, but then, the treble make the noise almost intolerable past the 5 o'clock.
4) in the OD2 is the unacepptable noise. past the 4 o'clock. it gets it veeeery noisy, and the volume in overall is low (3 or 4 o'clock in volume and mastervol)
1) the clean channel doesn't have a noticeable problem with the noise, until i get it to the top...well, middle actually (gain 7, MasterVol 7, and treble 10)...almost intolerable noise.
2) the crunch channel: doesn't have too much trouble, until i get it to more than 5 in treble (Gain 10, volume and MasterVol not so high actually more or less than 5)...almost intolerable.
3) OD1 doesn't have too much noise, even gain and volume doesn't have much to do, but then, the treble make the noise almost intolerable past the 5 o'clock.
4) in the OD2 is the unacepptable noise. past the 4 o'clock. it gets it veeeery noisy, and the volume in overall is low (3 or 4 o'clock in volume and mastervol)
Here is where I was trying to go. The OD channel path is:
input
IC4a
IC6a gain control stage
tone controls
IC6b buffer
contour control and volume control
IC7a
after that, the clean channel mixes in and they feed teh master volume.
IC4b is the input buffer for the clean channel
ANy control that affects the volume or tone of the noise is after the source of the noise, so if the tone controls affect it, then it is coming from before them. If the tone controls have an effect on the noise, then obviously everything later in the circuit will too, the master volume for example.
But back to those tone controls. The gain control is on IC6a. If it affects th amount of noise, then either UC6a is noist or something earlier. And pretty much the only thing earlier is IC4.
In the shop, I use a scope to look at noise on the signal path. But considering these are common 4558 op amps and they are very inexpensive, I would probably just replace IC4 and IC6 and find out if that was the solution.
input
IC4a
IC6a gain control stage
tone controls
IC6b buffer
contour control and volume control
IC7a
after that, the clean channel mixes in and they feed teh master volume.
IC4b is the input buffer for the clean channel
ANy control that affects the volume or tone of the noise is after the source of the noise, so if the tone controls affect it, then it is coming from before them. If the tone controls have an effect on the noise, then obviously everything later in the circuit will too, the master volume for example.
But back to those tone controls. The gain control is on IC6a. If it affects th amount of noise, then either UC6a is noist or something earlier. And pretty much the only thing earlier is IC4.
In the shop, I use a scope to look at noise on the signal path. But considering these are common 4558 op amps and they are very inexpensive, I would probably just replace IC4 and IC6 and find out if that was the solution.
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