Heatsink seems too warm ? Need help Please

[ppcblaster]

I built my first amp, a BrianGT Stereo. Avel 250VA 25 dual P & S.


Before I read the manual, I installed a 250K dual, cheap pot for a

volume control, (I could not get any PEC samples). . I found if I

turn the pot to zero ohms (full volume), and use my walkman

as a preamp the sound is better than anything I have heard in a

long time. I am worried about the heatsink temperature, it

seems too warm. I bought my heatsink from BOSS on ebay,

(I discovered him searching in this forum). 10mm plate big fins,

5 3/4" X 3". I am wondering if I goofed the star ground.

I searched here a long time, I will post pictures when I find a

camera. No hum, sounds good to me, Please explain the ground

star.

AC and DC, are they tied together?

35VDC on each rail, no DC at outputs.

Thank You...............

[Nordic]

You omitted to say if you are driveing 8 ohm loads or trying to kill something with 4 ohms. As you are not mentioning smoke I assume you have an 8R load.

Is it getting hot with no signal?
If so it may be oscillating

What is your concept of hot... how long can you keep your finger on it?

If you have no hum, you don't have to worry about the ground further I think.. ground star is used to give multiple parts of the circuit refference to the same ground point....

You will still go through a couple of stages in all likelyhood of understanding the subtleties of layout VS schematic design... I know I am still learning...

If it sounds good, its time to congratulate yourself... 250k pot is probaly way to big, and yes I think almost anything is better than a cheap pot...a source with its own volume control is ideal as the amp in all likelyhood sees a fixed impendance.

[ppcblaster]

Originally posted by Nordic
You omitted to say if you are driveing 8 ohm loads or trying to kill something with 4 ohms. As you are not mentioning smoke I assume you have an 8R load.

Is it getting hot with no signal?
If so it may be oscillating

What is your concept of hot... how long can you keep your finger on it?

If you have no hum, you don't have to worry about the ground further I think.. ground star is used to give multiple parts of the circuit refference to the same ground point....

You will still go through a couple of stages in all likelyhood of understanding the subtleties of layout VS schematic design... I know I am still learning...

If it sounds good, its time to congratulate yourself... 250k pot is probaly way to big, and yes I think almost anything is better than a cheap pot...a source with its own volume control is ideal as the amp in all likelyhood sees a fixed impendance.

100 F after 3 songs

[peranders]

100 deg F (38 deg C) is nothing, perfectly safe but you may check how hot the IC is. 10-15 deg C more is OK. Less is better of course.

[Nordic]

Dead on, don't think anything is wrong with it...

You will still learn the finger thermometer... pretty accurate for these kind of things...

[ppcblaster]

Thank you All

[AndrewT]

I found if I turn the pot to zero ohms (full volume)

Hi,
I don't understand this.
How have you wired the pot?

[jaycee]

my guess would be zero ohms between the wiper and the end of the track that's connected to the input.

[ppcblaster]

Originally posted by AndrewT
Hi,
I don't understand this.
How have you wired the pot?

I removed the pot 250K too much, I will replace it with something

else. Pot worked, not much adjustment...

[AndrewT]

Hi PPC,
did you wire up the pot as a variable series resistor or as a volume control?
Please tell us how you wired it up.