Oscilloscope audible whine, common? - Page 1
Forum section: electronics / beginners

author: Yej
author_rank: Newbie
timestamp: March 18, 2024, 06:34:22 pm
content: Hi, I've got a Tek MSO4 scope, is it common for the scope to have an audible whine while powered on? The whine is always there even with no probe connected and no matter what setting.I've never noticed it before but lately, I've been hearing it and it's getting pretty annoying.There is also a chirping noise when the power is on but the scope is turned-off, the chirp turns into a whine as soon as the scope is powered on.I tried to plug the scope into an entirely different electrical circuit ( not just a different outlet ), and it's almost as if the whine shifts to someplace else, this time there isn't any chirping. but a few seconds after Power-on the whine starts and it's as if the whine is noisy ( still continuous, but the frequency is all over the place )Could this be because of a wiring issue?

author: m k
author_rank: Super Contributor
timestamp: March 22, 2024, 06:05:16 pm
content: Maybe a choke and capacitor combined.Targeting by hearing can be tricky.

author: jwet
author_rank: Frequent Contributor
timestamp: March 22, 2024, 11:52:26 pm
content: Its not normal, it could be the line AC input but it would have to be way out of whack- like 25% low, etc. Find a known good outlet, and eliminate this. Something is failing in the power supply. There are some good Tek Repair groups online and it might be a known weakness and someone can lead you right to it. As the last poster said, likely an output filter cap or choke. Switching power supplies operate above hearing normally much much higher (100KHz).One of the problems with later model Tek scopes (and even HP Equipment) is that they farmed out the power supplies as an assembly from large PS OEM's like Delta, etc. Its usually a custom and though you'll find similar ones, you find the same on easily available. The service info can be scarce but there are people out there that have solutions.Good luck.

author: aliarifat794
author_rank: Regular Contributor
timestamp: March 23, 2024, 10:30:45 am
content: External factors such as nearby electronic devices, electromagnetic interference (EMI), or radio frequency interference (RFI) can create noise.

author: p.larner
author_rank: Frequent Contributor
timestamp: March 23, 2024, 10:44:22 am
content: maybe an inductor or transfo core cracked or loose?.

author: aliarifat794
author_rank: Regular Contributor
timestamp: March 24, 2024, 02:26:06 pm
content: Also, if you're comfortable with it, you could open up the scope (if it's out of warranty) and visually inspect the internal components for any signs of damage or loose connections.

author: Yej
author_rank: Newbie
timestamp: March 27, 2024, 06:51:59 pm
content: Hmmmmm.......guys. There is a full 240 between neutral and earth....

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 27, 2024, 08:20:41 pm
content: Quote from: Yej on March 27, 2024, 06:51:59 pmThat can be not good if you are talkng about a wall socket. But inside a device this can be ok.Wall socket types of most countries offer a possibility to insert a plug into a socket both ways.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 27, 2024, 09:14:16 pm
content: Quote from: m k on March 22, 2024, 06:05:16 pmHello, is there any other methodology in order to localize a magnetostriction noise source ?

author: Jwillis
author_rank: Super Contributor
timestamp: March 28, 2024, 04:00:56 am
content: Quote from: Coordonnée_chromatique on March 27, 2024, 09:14:16 pmI've used a wooded dowel like a doctors stethoscope. Hold one end to the ear and the other to a transformer or choke. But the noise can come from cracked varistors and ceramic caps as well. Even loose transistor on heat sinks. In any case, it's most likely to be in the switching power supply.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: March 28, 2024, 07:47:54 pm
content: Quote from: Jwillis on March 28, 2024, 04:00:56 amThe common practice is the use a array of microphones in the near field, we need a nano array of microphones ?