Thank you for your answer, it is a preassembled kit the power bridge and two cards with the LM3886, here attached the pics
Attachments
Many thanks for the advice, this was indeed my first thought but the Amp temperature remain stable low, you can easy keep in the fingers without feeling it warm, moreover in the datasheet is stating that the thermal protection enter when the chip reach 165C and it is actually really far from there....
I will try to add an heatsink and connect the ground to see if somenthing change....
I will try to add an heatsink and connect the ground to see if somenthing change....
Hi All,
Yesterday I performed a longer test and the problem is still present, the amp works fine for 90-120 seconds and then stops.
If the amp is completely cold it can sound for 150 seconds or more while if I wait only few seconds disconnected from the power supply it will last only 90. Not sure if is a thermal proble or is related to the capacitor charge, again I am a completely new in electronic.
Both chips are connected with the thermal grease to a pc heatsink and it does not seems to get warm while touching them, while it should not necessary I also added a small heatsink to the rectifier chip.
The strange thing is that both channel stop exactly at the same time so it makes me think the problem is in the power supply but measuring the voltage it seems stable.
So I am here without any clue to how solve the issue.
Any from you guys will be really appreciated.
Luca
Yesterday I performed a longer test and the problem is still present, the amp works fine for 90-120 seconds and then stops.
If the amp is completely cold it can sound for 150 seconds or more while if I wait only few seconds disconnected from the power supply it will last only 90. Not sure if is a thermal proble or is related to the capacitor charge, again I am a completely new in electronic.
Both chips are connected with the thermal grease to a pc heatsink and it does not seems to get warm while touching them, while it should not necessary I also added a small heatsink to the rectifier chip.
The strange thing is that both channel stop exactly at the same time so it makes me think the problem is in the power supply but measuring the voltage it seems stable.
So I am here without any clue to how solve the issue.
Any from you guys will be really appreciated.
Luca
Hi Luka.
The box you are using is a death trap. Use a closed metal box connected to safety ground so no one can touch live wiring. Even a biscuit tin with a lid would be safer than that.
The chips need fixing solidly to the heatsink either with a screw or bolt through the hole in the tab or a metal bar across the chip clamping it. Are your chips insulated types with plastic covered tab or is the back of your tab bare metal?
Your heatsink is way too small for 2 chips too.
John
The box you are using is a death trap. Use a closed metal box connected to safety ground so no one can touch live wiring. Even a biscuit tin with a lid would be safer than that.
The chips need fixing solidly to the heatsink either with a screw or bolt through the hole in the tab or a metal bar across the chip clamping it. Are your chips insulated types with plastic covered tab or is the back of your tab bare metal?
Your heatsink is way too small for 2 chips too.
John
Hi John,
Thanks for your suggestion, I am aware that is risky and is of course an absolutely temporary solution for testing purpose. I normally turn on the amp, execute test and then shutdown disconnecting the power supply.
I will look for a safer box, a bigger heatsink and of course to fix them solidily, however I am not sure this is the issue as both chips and heatsinks remains absolutely cold during the usage moreover I would be surprise considering that both channel stops at the same time.
The chips are insulated type.
I read also about grounding loop may can cause the problem... what do you think about that?
Thanks again for your advice.
Luca
Thanks for your suggestion, I am aware that is risky and is of course an absolutely temporary solution for testing purpose. I normally turn on the amp, execute test and then shutdown disconnecting the power supply.
I will look for a safer box, a bigger heatsink and of course to fix them solidily, however I am not sure this is the issue as both chips and heatsinks remains absolutely cold during the usage moreover I would be surprise considering that both channel stops at the same time.
The chips are insulated type.
I read also about grounding loop may can cause the problem... what do you think about that?
Thanks again for your advice.
Luca
Connect the two transformer together. The primaries parallel (220V) and the secondaries in serie (2x24V).
Connect the middle connection of the two secondaries to the "GND" connection on the PSU board. Connect the other two wires to the "26V" on the same board.
Best to post some photo's before testing.
Connect the middle connection of the two secondaries to the "GND" connection on the PSU board. Connect the other two wires to the "26V" on the same board.
Best to post some photo's before testing.
You should build a "bulb tester" and do you have a multimeter?
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html#post2200138
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html#post2200138
FINALLY IT WORKS!!
Yesterday night I put the two toroids in parallel, fixed the chips to a bigger heatsink and made some minor change on grounding configuration.
I am not sure what was the main contributor to fix the problem but now it is solved. I will look for a nice box to put everything in a definitive solution.
Thanks again you guys for the great support.
Luca
Yesterday night I put the two toroids in parallel, fixed the chips to a bigger heatsink and made some minor change on grounding configuration.
I am not sure what was the main contributor to fix the problem but now it is solved. I will look for a nice box to put everything in a definitive solution.
Thanks again you guys for the great support.
Luca
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