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Old 27th September 2003, 07:39 PM   #1
MaXiZ is offline MaXiZ  Italy
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Question First attempt to build a Power amp!

Hi to all! I've build a Power amp based on the TDA7250 that i think is a good amp and economic amp!
I use a SMPS as Power Supply. From +14 to +/-42V@2.2A that i think should be enough for this amp.
OR not?
My problem is that i don't ear no sound from it.. what should be? I know that maybe a mistake on soldering but
What are the main things to check...?
As Q1 and Q2 i've used TIP142/147 that should be enough to have 70W+
Click the image to open in full size.
Thanx in advance for all the suggest and to all the ppl that will give an answer...
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Old 27th September 2003, 08:47 PM   #2
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I have no clue what the problem is, but next time, please don't post the same question in 3 different forums.
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Old 27th September 2003, 08:50 PM   #3
Rarkov is offline Rarkov  England
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Firstly, as I'm sure you're aware...you only need to post this in one forum. Since the heart of this circuit is an IC, it should go in either the Car Audio or Chip Amps forums. If it is for a car then you have a choice - otherwise it should be in the Chip Amps. People will answer you if they want to and spam won't change that.

Assuming that all is soldered correctly (check for dry solder joints) then you should check pinouts (especially for short circuits at input signal, power supply and output signal.

Have you measured the voltage in the power supply at the pins of the chip?

Gaz
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Old 28th September 2003, 01:39 AM   #4
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Pretty complicated for first amp... you should stick with something like the LM3886...that was my first high power amp. After I figured out it needs a split supply and not a single, it worked the first time. www.national.com
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Old 28th September 2003, 02:26 AM   #5
mcp is offline mcp  United States
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Default TDA7250 - nice chip

Hi MaXiZ

Nothing wrong with chip. The schematic you showed is not meant for TIP142/147.

You can find some info here:
schematics
TDA7250 Amp
TDA7250 in Pro Use
Cheers
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Old 28th September 2003, 07:22 AM   #6
MaXiZ is offline MaXiZ  Italy
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Quote:
The schematic you showed is not meant for TIP142/147.
At http://www.ampslab.com/ia502schema.htm is reported to use the 142/147 and u say to don't use them.. why?
And i saw "input sensitivity 1v".. This mean that if my car stereo give and output of 30mV@360mA i can't hear nothing. Right?
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Old 28th September 2003, 08:25 AM   #7
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check your rails for power...if there is...check for any obvious connecion problems and heating...
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Old 28th September 2003, 08:26 AM   #8
MaXiZ is offline MaXiZ  Italy
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I?ve made some test.. And i've discovered this...
The circuit take 0.95A.. Normal?
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Old 28th September 2003, 08:27 AM   #9
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Can you also post a few pcitures...had to imagine what you are building frm here...hehe
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Old 28th September 2003, 08:31 AM   #10
MaXiZ is offline MaXiZ  Italy
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Quote:
Rarkov

Have you measured the voltage in the power supply at the pins of the chip?
Sure and the power is less than 1v so if i'm not wrong this mean that all the power is take from the circuit right?

Quote:
li_gangyi

Can you also post a few pcitures...had to imagine what you are building frm here...hehe
I'll make some now.. if u'll be patient!
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