Power Supply spike

surfsup · Post by **surfsup** » Tue Jul 17, 2012 4:36 pm

I have this spike at 125kHz, I believe. does anyone know what that is? Whether I have the amp unplugged (off) or not, I get this on the probe. If I disconnect the probe, I get a small cycling sine wave.

VacuumVoodoo · Post by **VacuumVoodoo** » Tue Jul 17, 2012 5:51 pm

130kHz to be exact. Whether the amp is powered on or not doesn't matter. All the wiring is one big spider web antenna and picks up whatever electronic smog there is in the air. This looks like something leaking from a SMPS. There's one in your PC.
I had a similar problem come up after I installed a LED ramp above my work bench. Turned the LED lighting off and all these spikes went away.

surfsup · Post by **surfsup** » Tue Jul 17, 2012 6:26 pm

ok thank you. I'm sure the downstairs neighbor must have stuff on as well...

Firestorm · Post by **Firestorm** » Tue Jul 17, 2012 6:30 pm

You live near Ohare? That's an aviation frequency range.

alvarezh · Post by **alvarezh** » Tue Jul 17, 2012 10:52 pm

Firestorm, he's talking about 125 KHz, aviation freq's are in Mhz. (108 to 136).

I learn a lot from your troubleshooting posts, keep them coming!

All the best.

surfsup · Post by **surfsup** » Tue Jul 17, 2012 11:43 pm

Not living near o'hare but apparently I do live close to some hellish electronic beast that spews out 130kHz noise...!

Thanks for looking...

Firestorm · Post by **Firestorm** » Wed Jul 18, 2012 4:10 am

alvarezh wrote:Firestorm, he's talking about 125 KHz, aviation freq's are in Mhz. (108 to 136).

Kilohertz ... megahertz ... what's a few orders of magnitude among friends?

VacuumVoodoo · Post by **VacuumVoodoo** » Wed Jul 18, 2012 6:55 am

surfsup wrote:Not living near o'hare but apparently I do live close to some hellish electronic beast that spews out 130kHz noise...!

Thanks for looking...

But can you hear it?...

surfsup · Post by **surfsup** » Wed Jul 18, 2012 11:38 am

I don't recall seeing this last year scoping the amp. I think I would have noticed it. No I don't hear it, but I don't have a mosquito problem this year either!

alvarezh · Post by **alvarezh** » Wed Jul 18, 2012 3:08 pm

@Firestorm:

Absolutely!

Cheers!

Jana · Post by **Jana** » Wed Jul 18, 2012 3:10 pm

Isn't that in the Bluetooth or RFID frequency band?

vibratoking · Post by **vibratoking** » Wed Jul 18, 2012 4:07 pm

Isn't that in the Bluetooth or RFID frequency band?

Bluetooth is 2.4 GHz
RFID is normally 900MHz with some GHz applications. Low frequency RFID is in the 125kHz range, but that is animal ID type stuff and 125kHz is VERY short range.

I doubt it's any of the above.

Roe · Post by **Roe** » Wed Jul 18, 2012 4:19 pm

try installing some snubbers and grid resistors

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