Leave older scopes on, or turn on/off more ? - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 26, 2019, 07:44:27 pm
content: I have a Tek2430A DSO and analog Tek2215, both from the 80's with CRTs. I'm playing with them today, and thinking the less I turn them on/off the better, so it's better just to leave them running rather than turning it on/off every 10 minutes or 1 minute.I'm worried they're going to blow up, I sure hope I'm in the room to unplug it and there's no fire.I should get a fire extinguisher, my bedroom is my LABWhat about turning down intensity on the CRTs, I keep them pretty low already, and on the tek2215 its just 1 knob to turn it right offOn the Tek2430A, I sometimes set the traces off screen, maybe that's good/bad too, I have 2 ideas each wayI can't wait to take these apart again when I get a 4ch Rigol scope this summer, I bet some caps in there should be checked at least. These need maintenance too, some switches acting up. And maybe a LV problem with the 2430A.

author: David Hess
author_rank: Super Contributor
timestamp: May 26, 2019, 09:06:45 pm
content: I turn mine off if I'm not using them for half an hour or so.Beware of leaving a CRO oscilloscope operating with the intensity turned to zero for long periods of time because this can result in premature aging of the cathode which is not designed to operate at zero current for extended periods of time. It is much better to leave the intensity low but visible and either defocus the beam or move it off of the screen if there is some reason to leave the oscilloscope on for days.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 27, 2019, 03:49:52 am
content: Back in the days of "all tube" devices, it was regarded as good practice to leave them running.This was mainly due to warm-up time affecting the stability of the equipment.With mainly solid state equipment, using SMPS (& CRTs), there are two major problems with this practice.(1) SMPS "start" circuitry often fails in a non destructive manner, so the power supply, once on, continues to operate happily, day after day, week after week.If a power failure happens, the SMPS will fail to restart.We had this happen with four Barco Picture Monitors, which were normally on 24/7 at my old job.After a power failure, the EPP took over, & everything came back, except these four Monitors.Picture Monitors are in great demand at TV Studios, so a major panic ensued to find replacements.After that, we turned them off from time to time, reasoning that at least we were prepared to fix one if it failed on our own "timetable".(2) Any device with a CRT, if left on continuously, will burn up filament hours, ultimately reducing its useful life.Apart from the above, & really a bit off topic, is when I was regularly called on to "degauss" a number of 27" Picture Monitors which lived in the various Studios.They were normally left on 24/7, by the Floor Manager & his team, & unlike the smaller rack mounted units, didn't have a "degauss" button, relying on the degaussing circuit operating at switch on.I started turning them off whenever I knew they weren't going to be used---- result:- No more " degaussing calls" plus longer CRT life.

author: tkamiya
author_rank: Super Contributor
timestamp: May 27, 2019, 04:24:35 pm
content: Fire extinguisher in lab is a good idea. I have two in my lab prominently mounted on wall. I also have two fire alarms. One in middle of ceiling and one near my work table. On top of it, I have it in my plan to install a big red emergency cut off switch to turn off everything at once.I usually keep my instruments off, especially scopes. Not that I'm afraid it's going to go up in flame but I don't like my CRT to have burn-in. I had capacitor pop but it never resulted in fire. Lots of smoke and they die in open. Keep in mind though, some stuff, especially precision equipment doesn't power off completely. They often keep oven or standard on.When I get used equipment, I open them up and clean and inspect in detail. If I think it's going to be a fire hazard, I either repair it, dispose of it, store it for parts, etc. I won't be using them, or worse, keep it on unattended.

author: Gyro
author_rank: Super Contributor
timestamp: May 27, 2019, 06:34:42 pm
content: I think this is more to do with keeping the internal components and insulation nice and dry from the heat of usage and keeping capacitors in good condition. Aluminium electrolytic caps like to be biased reasonably often to keep their dielectric films in good state. Tants seem to fail when equipment has been kept in cold / damp storage for long periods. Probably the same for Rifa caps but who knows when they will stop ticking.It's probably more important to make sure that the scopes get a decent warm-through when they are used (assuming that's at least every few weeks) but leaving them off the rest of the time to prevent deterioration of limited life components like the tube. Safer and greener too.

author: Ice-Tea
author_rank: Super Contributor
timestamp: May 27, 2019, 06:55:50 pm
content: My 0.02$: it's a choice between the PSU being at risk or the CRT wearinng out where the latter is a certainty, the first is not. If the PSU blows, there's a decent chance you'll be able to repair it. If the CRT goes, chances are you won't be able to replace it (at least not for a fair amount).

author: ogden
author_rank: Super Contributor
timestamp: May 27, 2019, 07:20:33 pm
content: Quote from: Ice-Tea on May 27, 2019, 06:55:50 pm^^^^^ this one. Obviously you leave it on during whole working day/session, in the end you turn it off. Modern test equipment requires warm-up as well. Usually 30 minutes. Keysight note: "Specifications are valid after a 30-minute warm-up period and ± 10 °C from firmware calibration temperature.". R&S note: "Three hours storage at ambient temperature followed by 30 minutes warm-up operation.".

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2019, 08:07:27 pm
content: I considered warm up time when I gave my answer of half an hour or more. I rarely find drift to be significant after 5 minutes.But I would not hesitate to leave one of my vector CRO oscilloscopes operating for hours at a time as required.