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Old Feb 25, 2012, 06:05 PM
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Austria
Joined Jan 2010
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Help!
Racewood 900MHz video tx - need to identify damaged SMD component

I have a Racewood 900MHz 500mW video transmitter (possibly the same as Range Video and LawMate units of the same spec?) which I have damaged in a botched attempt to replace the SMA connector. In trying to desolder the connector from the PCB I appear to have used too much heat and inadvertently damaged a nearby SMD component. I believe the component is a capacitor however it has no markings and I have no way to measure the value even if it were functioning correctly.

The attached images are of an identical unit found via Google, my camera couldn't get a clear shot that close. The circled component is what I'm looking to identify. Does anyone know what I need here? Maybe someone is able to calculate the value of a replacement? Thanks in advance!

Similar transmitter: http://www.dronesvision.com/racewood...r-green-label/
Image source: http://esquinaelectronica.blogspot.c...ansmitter.html
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Old Feb 26, 2012, 10:20 AM
The Fixer
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Canada, ON, Milton
Joined Jan 2009
3,854 Posts
That is a capicator and value would be 100pf.
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Old Feb 26, 2012, 11:03 AM
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Austria
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Thanks Martin! I saw that value on a 900MHz amplifier schematic but was unsure if it was relevant.

I've taken your word for it and already have a pack of replacements on the way, but as I'm still curious could you please tell me how you worked it out?
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Old Feb 26, 2012, 02:35 PM
Dave the Rave
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In my (humble, and often wrong) opinion, that SMD cap would be rather difficult to destroy just trying to de-solder the jack, even if you did use a lot of heat. They're pretty rugged. Check for something else, like a trace that lifted from the PCB and is broken, or a solder bridge, something like that. If the new cap doesn't fix it, post some info on exactly what the radio is or isn't doing, and one of the "gurus" on here might be able to point you in the right direction.

Now that I've said all that, the new cap is almost certain to fix it.
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Old Feb 26, 2012, 03:03 PM
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Thanks for the input Dave. Unfortunately there is no question about the cap being destroyed, I just didn't specify how I know because of how embarrassing it is! The contact on one side of the cap is physically missing, presumably in the middle of a glob of solder in the trash, and all that is visible on that side is ceramic and a little circle of something dark and conductive.

Fortunately I have made two very important upgrades since this mishap: I now have a proper temperature controlled soldering station instead of my previous $10 iron, and perhaps even more critically my first pair of much needed reading glasses.

Just as a quick note, I measured the damaged cap and it appears to be 0603 size (1608 metric). The replacements I ordered are here.
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Old Feb 26, 2012, 06:06 PM
The Fixer
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That will work.
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Old Feb 27, 2012, 11:46 PM
"Simplify, then add lightness"
Raleigh,NC
Joined Nov 2000
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Quote:
In my (humble, and often wrong) opinion, that SMD cap would be rather difficult to destroy just trying to de-solder the jack, even if you did use a lot of heat. They're pretty rugged.
They are fairly rugged after they are soldered on and cooled properly. However, the ends can crack fairly easily due to stresses from soldering especially if cooled too quickly or heated unevenly. I have done quite a lot of commercial PCB bringup and repair and have found very many that were bad with no external signs of a crack. However when replacing the caps one or the other end would fall right off.
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Last edited by jeffs555; Feb 27, 2012 at 11:52 PM.
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