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Old 17th Aug 2016, 12:11 pm   #1
stuart_morgan_64
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Default IC polarity

I feel stupid asking, but I am struggling to get a fluorescent power meter to work on a amplifier.

Pin 1 is the one on the left? Pin 1 is the one marked on the board?

I have power to the IC. Signal to the IC. However voltage at power pin is full VCC, 45v, its dropped via a 1.8K which is fine. It seems the IC isn't drawing any current to drop the voltage.

This is the second IC.

Just making sure it is in correctly. Thanks
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Old 17th Aug 2016, 12:17 pm   #2
richrussell
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Default Re: IC polarity

Usually pin 1 is marked by a dot or a missing corner. So yes - I would assume that pin 1 is the one on the left in your photo.
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Old 17th Aug 2016, 12:28 pm   #3
'LIVEWIRE?'
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Default Re: IC polarity

DIL ICs, such as that one,have pin 1 to the front LH side when viewed from above. As richrussell says, there is usually an ident such as a dot close to pin1, or often a small notch between the two end pins at the pin 1 end.
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Old 17th Aug 2016, 12:48 pm   #4
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Default Re: IC polarity

But that looks like a SIL IC......
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Old 17th Aug 2016, 12:50 pm   #5
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Default Re: IC polarity

So it does, in which case pin one is the left hand end, with the corner clipped. Duff batch or counterfeit chips?
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Old 17th Aug 2016, 12:51 pm   #6
GeoffK
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Default Re: IC polarity

This might help.
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Old 17th Aug 2016, 12:52 pm   #7
Malcolm G6ANZ
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Default Re: IC polarity

Reading the number as TA7318. AllDatasheet.com gives this PDF
http://www.alldatasheet.com/datashee...A/TA7318P.html

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Old 17th Aug 2016, 12:59 pm   #8
stuart_morgan_64
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Default Re: IC polarity

Hya thanks all, yes it's a sil. I did look at the data sheet too, but thought maybe i was missing something.

Just wanted to make sure I hadn't woken up a bit more barking mad.

Thanks
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Old 17th Aug 2016, 1:38 pm   #9
Andrew B
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Default Re: IC polarity

I see pin 1 as ground and pin 9 as Vcc
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Old 17th Aug 2016, 4:50 pm   #10
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Default Re: IC polarity

Quote:
I see pin 1 as ground and pin 9 as Vcc
As most chips behave like a diode across the GND and VCC (diode conducting the wrong way round for more than 0.6V) an ohm meter may help in confirming the 'polarity'.

Last edited by Guest; 17th Aug 2016 at 4:52 pm. Reason: Using works keyboard for ages, different spacing from the laptop, this edit explanation took ages to get right too!
 
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