Question About the LM317 temperature

[LucaVilla]

Dear All, I completed the AMP10 and I am very surprised about its power and quality of the sound, amazing stereo effects, dynamics! My question is about the temperature in LM317 regulator, the metal heat is at 100°C fixed the TA2022 is about 60°C my power trasformer is a 24+24 VAC 160VA. I am quite bit worried about the 100°c on the LM317. I didnt find a 22+22VC trasfo. I read the LM317 technical specifications and they tell it can run with voltage input of 40VDc. I am using the AMP since 2 weeks and for many hours continuosly (need to discover all my music tracks again with this super AMP :-) ). Do you think I am going into trouble to have this high temperature on LM317? I think for the TA2022 60°c is not so bad, also I noticed it plays better when it is in temperature... . Thanks to everybody!
Best Regards!

[FFF]

60 and 100'C seems pretty hot to me in any case!
I personally would not use it before I got that fixed.
Better give a description of the heatsinks used??

[V-bro]

It's waaay too hot!!

Indeed don't use it until this is fixed!

And indeed post us some pics wil you?

Did you copy that 24-0-24 from the specs or did you measure that? If it is from the specs it is even more worrying!!

[Scratchy]

Are you using a heatsink on the TA2022? 60°C is far too hot for this chip.
Mine runs stone cold. The heatsink is at room temperature.

[LucaVilla]

Hi to everybody here! I am not using any heatsink for both the chips. 24-0-24 I misured with no load on the trasfo. I have about 33-34 V DC on the big capacitors. I am going to mount a heatsink on the LM317 and TA2022, but anyway I am using the AMP since 3 weeks and no problem, it sounds fantastic!!. I will post soon some Pics of it! thanks a lot for your answers and I will update you. REGARDS!

[V-bro]

Hmmm, I'm sure the assembly instructions mention something like needing a heatsink... well it's amazing it still works! Speaks for the parts quality!

[LucaVilla]

Hmmm, I'm sure the assembly instructions mention something like needing a heatsink... well it's amazing it still works! Speaks for the parts quality!

Yes for sure I will add an heatsink for both, anyway the OPERATING CONDITIONS for TA2022 from their datasheet is max +/- 36VDC , normal voltage is +/- 31VDC and for LM317 is 40VDC. In the mounting manual there is a section about the heatsink but not about max temp it can reach. Thanks for the reply. REGARDS

[V-bro]

Make sure you mount the heatsinks isolated! So use mica+paste or silicone pads!

[flitgus]

The temperature of the TA2022 depends also on how loud your listening to your music. The more power you're drawing from the amplifier, the more heat the chip will need to dissipate. Look a the datasheet for determining how warm the chip casing can be for safe operation, with or without heatsink. If it's 60 deg celsius when you're playing loud, i think it's safe.

Regarding the regulator. If i'm remembering right, the regulator is expected to output up to 80 mA at 5V. If there was no resistor in front of the regulator, it would have to dissipate (34-5)*80*10e-3 = 2.3 W in the worst case (neglecting here the diode effect).

Now, there's a thick resistor in front of the regulator, which is going to lower the input voltage that the regulator sees. This resistor is 47 ohms, so that the voltage seen by the regulator is 34 - 47 * 80*10e-3 ~= 30 V, hence the power to be dissipated is lowered to 2 W.

Given that your power supply is at the limit of the specifications, you might want to raise the value of this resistor in order to decrease further the voltage seen by the regulator. Take care however that the same resistor is also part of a RC lowpass filter in combination with the capacitor that's following (220 uF). Indeed, if you change the resistor without changing also the capacitor, you'll alter the cutoff frequency of the filter.

Hope that helps.