Curiosity

[Periproct]

Just curious here.

I managed to break the tiny coaxial connector on my express card TV tuner.
Decided to remove the connector from the PCB, cut the small coaxial plug off
the supplied lead and solder it directly to PCB.
Having got the connector off the PCB I checked for shorts with a multimeter
and got 1.1 ohms. Couldn't see any solder shorts so thought maybe I'd
overheated a component. Decided to connect up the lead anyway and the tuner
works fine.

Why do I see a short at DC but obviously not at UHF? Inductor?

 

[Michael Black]

On Tue, 22 Sep 2009, Periproct wrote:

Just curious here.

I managed to break the tiny coaxial connector on my express card TV tuner.
Decided to remove the connector from the PCB, cut the small coaxial plug off
the supplied lead and solder it directly to PCB.
Having got the connector off the PCB I checked for shorts with a multimeter
and got 1.1 ohms. Couldn't see any solder shorts so thought maybe I'd
overheated a component. Decided to connect up the lead anyway and the tuner
works fine.

Why do I see a short at DC but obviously not at UHF? Inductor?

You only interpret it as a short.

There is likely a coil there for coupling to the next bit of circuitry,
and of course when you measure it wiht an ohmmeter it will appear to be a
"short". But it doesn't take much of a coil at that frequency, and you'd
need much better equipment to see anything but a short, even though it's a
perfectly legitimate coil at the desired frequencies.

Michael

 

[Periproct]

"Michael Black" <et472@ncf.ca> wrote in message
newsine.LNX.4.64.0909221835500.28021@darkstar.example.net...

On Tue, 22 Sep 2009, Periproct wrote:

Just curious here.

I managed to break the tiny coaxial connector on my express card TV
tuner.
Decided to remove the connector from the PCB, cut the small coaxial plug
off
the supplied lead and solder it directly to PCB.
Having got the connector off the PCB I checked for shorts with a
multimeter
and got 1.1 ohms. Couldn't see any solder shorts so thought maybe I'd
overheated a component. Decided to connect up the lead anyway and the
tuner
works fine.

Why do I see a short at DC but obviously not at UHF? Inductor?

You only interpret it as a short.

There is likely a coil there for coupling to the next bit of circuitry,
and of course when you measure it wiht an ohmmeter it will appear to be a
"short". But it doesn't take much of a coil at that frequency, and you'd
need much better equipment to see anything but a short, even though it's a
perfectly legitimate coil at the desired frequencies.

Thanks for the reply.

I nearly binned the tuner thinking I'd killed it. Glad I went ahead with the
repair as it was an impulse purchase and I probably wouldn't have bothered
to replace it.