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Weird issue TDA7377 amplifier

Audioguru

Sep 24, 2016
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With a 12V supply and two 8 ohm speakers then the power output and heating are not much unless you play continuous tones instead of music. Maybe the Asian design causes the amplifier to continuously oscillate at a very high frequency that will overheat it.
 

Sidecar Bob

Dec 19, 2021
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I just connected it to a couple of "4-6Ω" speakers (ohmmeter says 4Ω and I'm not set up to measure impedance so I'll assume resistance = impedance) and played music through them louder than I'm likely to run the 8Ω speakers in the garage (that I'm sure are more efficient) for and let it run while I did something upstairs for 1/2 hr. (trying for a worst case test).
While it was still playing I checked the temperature with the IR thermometer and found 50c on the chip and, 47c on the opposite side of the heatsink and below 30 at the ends of the heatsink.

Conclusion: It definitely needs vents and a fan wouldn't hurt. I just ordered some 40mm fans for about $1.70 each.
 

Audioguru

Sep 24, 2016
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The heatsink should be on the open on the end of the circuit board with hot air rising from it and cool air from below replacing the air.
The circuit board blocks air motion.
 

Sidecar Bob

Dec 19, 2021
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I don't have a lot of choice with the heatsink in the middle of the board like that. Perhaps I could attach the fan to the heatsink, blowing into it and put vents on both ends and directly above the middle of the heatsink so that air will enter at the ends and exit upward.
 

bertus

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Nov 8, 2019
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Hello,

The heatsink ik shiny aluminium. That is not the best for radiation.
See this section of the posted article:
Radiation requires that the surface has the maximum emissivity of heat, and this means that its colour is important.
Shiny gold anodised heatsinks might look great (if you like that sort of thing), but are hopeless at radiating heat.
It's no accident that the radiator in a car, or the condenser on the back of a refrigerator is matte black - not chrome plated and shiny.
Matte black heatsinks are the best for radiation, and will have a significantly better thermal resistance than any other.
Use of paint is to be avoided however, unless kept thin and even.
A thick layer of paint acts as an insulator, reducing the ability of all those unwanted therms to get out into the air.

Bertus
 

Sidecar Bob

Dec 19, 2021
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They sell "high performance" car radiators in bare aluminum. I'm not sure how the emissivity of that works but I think it may have to do with avoiding the insulating effect of the paint, although standard radiators are usually painted.

At any rate, it is nice to talk about black heatsinks being more efficient but I'm sure most of us are not equipped to anodize aluminum and lots of much higher powered devices have plain aluminum heatsinks.
If the heatsink is big enough a plain aluminum one will be adequate and I expect that is the case for this one.

I am far more concerned about moving the heat it does radiate out of the plastic project box it will be mounted inside and I think adding a fan and vents as I described will probably accomplish that.
 

ramussons

Jun 10, 2014
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I think not. Since adding the missing cap fixed the issue, it's good now, isn't it?

Or do you refer to the discussion about power output? In that case I agree.
I was referring to the initial discussions being hijacked to power output.
 

Audioguru

Sep 24, 2016
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I hijacked the original muting problem because nobody explained how adding a missing capacitor to ground fixed the DC muting.
The amplifier output power was low due to the low supply voltage and speakers being a home's 8 ohms instead of a car's 4 ohms.
The Taiwan amplifier IC that had the heatsink lying down in the middle of the circuit board get hot because the heatsink had no air flow.

The datasheet for the amplifier IC shows a 2.1 amplifier with the left and right channels out-of-phase without mentioning it.
 

Harald Kapp

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nobody explained how adding a missing capacitor to ground fixed the DC muting.
This capacitor is required acc. to the datasheet. I think it is not explained why it is needed there either. Possibly to suppress stray noise which causes muting.
 

bertus

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Hello,

As said, page 6 of the attached UTC datasheet shows the signal at the standby and diagnostic pins.
(see post #14).

Bertus
 
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