Tests to help predict that failure is near  - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 23, 2015, 12:36:58 pm
content: Hi,I'm sure the very helpful bunch here can helpI just bought 4x the amount of switches I need for a project, the switches are all well used, no doubt running 24/7 for most of the last decade.They are Nortel switches, I am going to use them in pairs so that a failed switch won't cause an outage.I will power them on and look and listen for issues.How would I go about figuring out which ones to use initially (the ones with the best chance of surviving the longest), open them up, use a DMM on fans and PSU's, oscilloscope, should I go as far as trying to get new fans and/or PSU's?Thank for looking.CheersRichard

author: Simon
author_rank: Unknown
timestamp: April 23, 2015, 12:38:58 pm
content: Wear on a switched will be caused by operating them more than just passing current, that I'm aware unless they rattle or feel ropy when operating there is no way to tell.

author: BradC
author_rank: Super Contributor
timestamp: April 23, 2015, 12:43:56 pm
content: Quote from: Simon on April 23, 2015, 12:38:58 pmI don't think you are talking about the same kind of switchThe biggest failure points of any gear like that are the PSU's and the fans. Have a visual inspection of the PSU's, and replace the fans. Most quality gear (and I do count Nortel there) is/was made to last, so you'll probably be ok. I've used loads of second hand switches / routers, and the only failure I've had was the PSU in a Cisco 3550 getting iffy on startup when cold. Easy to fix. I look for gear with low speed blowers rather than axial fans, but you have to take what you can get sometimes.Put 'em in and use them. Just keep a spare handy.

author: Simon
author_rank: Unknown
timestamp: April 23, 2015, 01:30:02 pm
content: oh that sort......

author: Kjelt
author_rank: Super Contributor
timestamp: April 23, 2015, 02:58:52 pm
content: Yes better to call it a network switch or ethernet switch.Indeed as suggested replacing the fans would be a good precaution although most modern switches detect and report failures by measuring the pwm of the fan.If you use them for personal home use, try replacing the fans with one from Noctua from Austria which will reduce the sound with tens of dB's (did this myself last week for a few 10Gbe Dlink switches).Look at the internal powersupply and pcb for visual signs like discolorization (to hot) and preventive replacing the critical electrolytic capacitors with an A-brand.Also check if the coolingplates are still stuck and clean out any dust.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 23, 2015, 04:07:41 pm
content: I'm not aware of any tests for determining that, unless you are HAL9000 and you grow tired of your co-workers.You can look into the various reliability predictors.http://www.reliasoft.com/newsletter/v9i1/prediction_methods.htm

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 24, 2015, 05:28:57 am
content: Thanks everyone!

author: babysitter
author_rank: Frequent Contributor
timestamp: April 24, 2015, 05:38:33 am
content: First, put a buttload of traffic thru them, from as many clients as possible, and get them close to maximum ambient temperature with the help of a oven. Watch traffic for degrading, resets, blinking power LEDs.If they are manageable see if there are signs of problems visible on the web interface - unstable supply voltages, Fan RPM rates, permanent error flags if such things are available.If you want to crack them open, look for brownish coloring or other signs of heating, I would replace the fans only if slow, starting up bad or dusty as hell. You might consider cleaning heatsinks etc. as preventative measure.

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 24, 2015, 07:54:17 am
content: Thanks babysitter, I will do some of that