Hi everybody,
I have 2 Tannoy SFX5.1 subwoofers, one powered by a TDA7293 and the other one by a TDA7294.
Both subwoofers are "working", so sound is good at very low volume, but as soon as i rise up the volume more than 20% it starts to heavily distort .
I suspected the speakers at the beginning, and i tried to use other speaker that i know is good, but i get the same result.
Can a TDA IC be like semi-damaged, so it still kind-of-works, but distorts? (so changing it may solve the problem)...
Is there any other thing i should check? (i measured all the resistors and diodes in the circuit and all are fine, i cleaned the board of the glue(i read somewhere that this glue can became conductive over time), and i also visually inspected all the caps, and all are looking good, no leaks or deformation, i visually inspected the pre-amp area and everything looks fine)...
LE: I just checked it with an oscilloscope using a 40HZ signal, and the wave stays clean up to ~40% of the volume, then clips. Signal supplied from an Ipad.
Thanks for your help!
I have 2 Tannoy SFX5.1 subwoofers, one powered by a TDA7293 and the other one by a TDA7294.
Both subwoofers are "working", so sound is good at very low volume, but as soon as i rise up the volume more than 20% it starts to heavily distort .
I suspected the speakers at the beginning, and i tried to use other speaker that i know is good, but i get the same result.
Can a TDA IC be like semi-damaged, so it still kind-of-works, but distorts? (so changing it may solve the problem)...
Is there any other thing i should check? (i measured all the resistors and diodes in the circuit and all are fine, i cleaned the board of the glue(i read somewhere that this glue can became conductive over time), and i also visually inspected all the caps, and all are looking good, no leaks or deformation, i visually inspected the pre-amp area and everything looks fine)...
LE: I just checked it with an oscilloscope using a 40HZ signal, and the wave stays clean up to ~40% of the volume, then clips. Signal supplied from an Ipad.
Thanks for your help!
Last edited:
Have You checked the PSU rail voltages ?
It doesn't make sense testing components without checking the PSU first.
According to another board the IC should be a 7293 and not a 7294. Was it repaired before ? Check also Q151 and Q152 they say they get hot and discolored.
It doesn't make sense testing components without checking the PSU first.
According to another board the IC should be a 7293 and not a 7294. Was it repaired before ? Check also Q151 and Q152 they say they get hot and discolored.
Hi,
yes i checked, i have the right voltage, ~ +-43V (if i remember well) measured yesterday.
2SC1815 and 2SA1015 were changed (that was initial issue).
I also changed the IC (on the TDA7293board) with a new chip, and behavior is identical.
I've seen a bunch of capacitors on the board... can any of those possible cause the issue? I am talking specially about those on the input and output...
Yesterday when i measured with oscilloscope i had 25V measured when playing 20Hz sine wave before amp would go to clip. Is that OK, or i should have more?
Thanks!
yes i checked, i have the right voltage, ~ +-43V (if i remember well) measured yesterday.
2SC1815 and 2SA1015 were changed (that was initial issue).
I also changed the IC (on the TDA7293board) with a new chip, and behavior is identical.
I've seen a bunch of capacitors on the board... can any of those possible cause the issue? I am talking specially about those on the input and output...
Yesterday when i measured with oscilloscope i had 25V measured when playing 20Hz sine wave before amp would go to clip. Is that OK, or i should have more?
Thanks!
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