Tda 2052 60w amplifier problem.

[artois]

Hi guys,
i build this amp it sounds great there is only one problem, after the amp heats up a bit the one channel goes high volume and the other seems to die a bit. I have changed both chips just to make sure its not the ic's but it still happens. Ive removed all traces of flux and there are no shorts. I added a fan and it helped a while but as soon as u push up the volume the same happens. The 2052's are on a large heatsink with paste and insulated. I know they have protection but they are deff not over heating. Ive changed the pre-amp (ins) around so to check if its not the pre-amp. Something is going cuckoo as it heats up a bit. All comp are as specs. I'll ad the pcb and schematic. I think it might be some cap malfunction. I re-soldered all points and the transformer is 160va and is not near the board and is cool. Please help needed.
Txs john

 

[alec_t]

All comp are as specs

Did you test all comps at room temperature or when heated? Does the tone change with volume?
Is it always the same amp which goes high volume?
If you've resoldered all joints I assume we can rule out dry joints. Try replacing C1, R3 and R4.

Ive changed the pre-amp (ins) around

Do you mean you swapped the inputs to the pre-amp, or the inputs to the power amps from the pre-amp output?

 

[artois]

Hi alec,
i changed the outputs around from the pre amp to the amp to see if it was the pre amp its not the pre amp.you ask if the tone changes when it goes cuckoo,yes it does a lot treble,and the other amp seems to decrease in volume.yes always only the one side.i have not checked the components when it gets hot, by the time i get to doing so it has already cooled off and healed itself again frustrating i suspect one cap.

 

[audioguru]

The TDA2052 produces 60 Whats of "music power" with horrible 10% clipping distortion for only one second when its load is 4 ohms and its supply is 45V. Its datasheet shows that it clips when its output is only 17 Watts continuously into 8 ohms with a 36V supply, or 32 Watts continuously into 4 ohms.
It clips at 33 Watts continuously into 8 ohms with a 44V supply.

We don't know what is your speaker impedance and we don't know what is your total power supply voltage.

 

[artois]

Hi scrooge
im using 4 ohm speakers and my power supply is 25v-o-25v rectified.

 

[audioguru]

Plus and minus 25VDC is its max allowed supply voltage. With a 4 ohm load then it will get extremely hot when playing fairly loudly.
The datasheet shows that with a plus and minus 18V supply and a 4 ohm load its output at clipping is 26 Watts and its heating is 15W.
It might produce 50 Watts in your circuit and it might heat with close to 50W so it needs a huge heatsink, a fan and maybe liquid nitrogen.

 

[artois]

hi scrooge and all,
the amp is on a very large heatsink and like i said does not get very hot even near to its level of thermol shutdown im trying to figure out why just the one channel mis-behaves. check pic attach and u will see the heatsink. thanks all for trying to help out i hope i can get this sorted out. suggestions pls.
yxs john

 

[alec_t]

If the treble increases (or the lower frequencies get lost) when things get hot then my guess would be C1 or C3 is changing capacitance, or has a dodgy internal connection, and should be replaced.