Point 2 Point (no PCB) for TDA7293, TDA7294, TDA7295, TDA7296. - Page 8 - diyAudio
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Old 24th February 2013, 11:31 PM   #71
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In my psu ,one of the power supply LED goes off instantly, the other one few secs or minutes.Yes I agree with pot ,,the higher The noisier.I will try 1 u in parallel.
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Old 25th February 2013, 01:45 AM   #72
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Quote:
Originally Posted by simply14prem View Post
In my psu, one of the power supply LED goes off instantly, the other one few secs or minutes.
Fault detected!

Check amplifier for DC offset.
Check resistor values for standby and mute.
If no errors found at amp, then. . .
Check drainer resistors to see if one broke.
Transformer or bridge rectifier may have a fault.

(fault could be lopsided load or lopsided ac or bad bridge rectifier)

p.s.
It is also possible to have an "almost" failed shorted cap in the power supply board and/or amp power cap and in this case we'd have to swap caps one at a time until the bad cap is found. The very resistant, partially failed cap acts a lot like a backwards cap. We'd begin repairs by changing out whichever caps are the warmest, since erroneously shunting the power supply makes a little bit more heat.
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Last edited by danielwritesbac; 25th February 2013 at 01:55 AM.
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Old 25th February 2013, 06:04 AM   #73
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So ,,what should the LED function when off,,,should it go off instantly or a few seconds.
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Old 25th February 2013, 08:11 AM   #74
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Originally Posted by simply14prem View Post
So ,,what should the LED function when off, should it go off instantly or a few seconds.
They should not go off instantly except for when the amplifier is playing loud (high workload) at the time mains are disconnected.

More importantly, the LED's should turn off at approximately the same time.

You can create a 50/50 voltage divider with identical pair of resistors in series and that connects from V+ to V-, whereby centerpoint is virtual ground (perfectly half of the total) and then measure from virtual ground with your voltmeter to 0v to measure how many volts of asymmetry error.
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Old 25th February 2013, 08:16 AM   #75
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I just found out that my front speakers are causing the unequal discharging of the led...Must have done something wrong in wiring the co-axial speakers,
Without it the led turns off equally.

Last edited by simply14prem; 25th February 2013 at 08:18 AM.
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Old 25th February 2013, 08:58 AM   #76
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Originally Posted by simply14prem View Post
I just found out that my front speakers are causing the unequal discharging of the led...Must have done something wrong in wiring the co-axial speakers, Without it the led turns off equally.
SO, this information is that the asymmetry happens when there is a load attached to the amp, but not when the load is removed.

Asymmetry when loaded:
The bridge rectifiers and transformer need checked.
Also check the PI filters to see that the resistors are healthy and their bypass diodes are in useful orientation.
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Old 25th February 2013, 10:36 AM   #77
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Originally Posted by danielwritesbac View Post
SO, this information is that the asymmetry happens when there is a load attached to the amp, but not when the load is removed.

Asymmetry when loaded:
The bridge rectifiers and transformer need checked.
Also check the PI filters to see that the resistors are healthy and their bypass diodes are in useful orientation.
When there is load there is just 0.1 or .2 V difference.The diode is opposite to each other.I think everything is fine but..
My amp gives 12, or 11mv dc offset.
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Old 25th February 2013, 11:30 AM   #78
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My left front speaker is the problem.The other speaker doesn't give any problem.
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Old 25th February 2013, 02:58 PM   #79
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Originally Posted by simply14prem View Post
My left front speaker is the problem.The other speaker doesn't give any problem.
Interesting. I wonder why the front left speaker would resist far more in one direction than the other (asymmetric load). Perhaps it has a bad cap in the crossover? I do not know. But, you can find out by swapping parts from the left speaker to the right speaker until you find the one part that also relocates the problem, and then that part needs replaced.
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Last edited by danielwritesbac; 25th February 2013 at 03:01 PM.
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Old 25th February 2013, 03:52 PM   #80
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Originally Posted by danielwritesbac View Post
Interesting. I wonder why the front left speaker would resist far more in one direction than the other (asymmetric load). Perhaps it has a bad cap in the crossover? I do not know. But, you can find out by swapping parts from the left speaker to the right speaker until you find the one part that also relocates the problem, and then that part needs replaced.
I think my drivers are old needs replacing.I have remove the tweeter cap ,,but still the same problem..I will try change a speaker in the same cable,,,or i will change the cable..or swaping of the two drivers...every trick...but I think the speaker ,woofer is the trouble.
Anyway Im getting adapted to this tda7294 sound.I think i love the sound.
Edit; Now I know the uses of the LED

Last edited by simply14prem; 25th February 2013 at 03:56 PM.
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