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I need advice on a project im building

rob_croxford

Aug 3, 2010
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Ok firstly is their power gettin to the circuit?? have you checked all the solder joints for shorts and dry solder? is it a possiblity that you have miss handled the IC and sussepted it to static discharge??

can you please give some more information on the symptoms of this fault?

Pictures of your work would be nice too :)
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Take pictures of the board, from both sides. Preferably in natural light and detailed enough to read all the markings on the board.

Scans or photos of the circuit diagram may also be useful.

Also a description of exactly what it does and does not do would be great.

If it appears to do nothing, then please measure the current drawn by it.

edit: Looks like the device published in Silicon Chip Apr 2001
 
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jacob88

Apr 13, 2011
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ok ill post pictures 2moro cos its night where i am and ive checked the soldering and thats fine i was very careful when handling the components so i dont think its that ive also checked the circuit with a voltmeter and its fine my only issue is tuning and i cant describe it very well so ill explain more when i post pics 2moro

oh and ill scan the instructions i got with the circuit too
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Is this the circuit?

attachment.php


You should expect it to draw about 10mA.

If it is wired up as in this diagram, a mistake around the DC input jack could short out the battery.

Also it doesn't tune all the way down to 88MHz, or all the way up to 108MHz, so if your receiver is set near one of these extremes it won't find it.

Does your receiver have auto tuning, or is it manual?
 

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jacob88

Apr 13, 2011
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it is the circuit but its an older diagram so a couple of things are different ill post the diagram i got 2moro cos im going 2 bed
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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OK, some of those are seriously out of focus, but I can see enough to suggest a few things.

Firstly it appears that your joints use a little too much solder as some of them appear more as balls than a meniscus from the pad to the lead. This can mask poor joints.

The one thing I recommend you do first is measure the current drawn from the battery when the device is switched on and off.

Then measure the voltage between the -ve terminal of the battery and pins 7, 10, and 15 of the IC (with the power applied).

Then measure the resistance (with the battery removed) between the -ve terminal of the battery holder and pins 3, 8, and 12 if the IC.
 

jacob88

Apr 13, 2011
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Ok i've done that but what should the voltages be?
got a rough estimate?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Perhaps you should tell us what you get.

I would be expecting 10mA, 1.5, 0.7?, 0.7?, 0, 0, and 0.

However I'm looking for reasonable values. I can probably judge reasonable from what you measure more easily than you can from some vague estimate of what I may expect.
 
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