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Problem with amplifier built on TDA7250 chip

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jzaghal

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Problem TDA7250 ??

Hi Everybody,

I have built an amplifier around this chip.
It uses BDW93C and BDW94C Darlington output.

The Power Supply is arround +/- 30 Volts.
The design works beautifully, very clean output that goes
in the 200KHz range.

However .....

One little annoying problem, which I could not solve:

Only CH1 quiescent current is high at arround 130 mA.
CH2 is perfectly alright.

I measure the voltage between the -ve Supply and the Collector
of the PNP, on CH1 measures 0.013V (across the 0.1 Ohm ).
CH2 voltage is 0.00V which is as it should be.

Of course CH1 gets warm after a while, but waste of power.
I changed the TDA, but same problem.

Finally I used the same circuit that Gulson has used.
Any help appreciated.

Thanks 8O 8O
 

sounds like your zobial network coil is wound the wrong way {in the wrong direction}

or the tollerance of the resistors used is not 1% all round .5w carbon

always use carbon film with audio it is far more stable {the blue ones}

also maybe your load isnt quite right and check for ground problems

it can be as simple as the orientations of the resistors

also dont forget to isolate the chip form the heatsink
and connect the heatsink to gnd using a .1uf ceramic cap
 

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