Beryllia in my scope + weird trace glitch (Farnell DTC12 analogue) - Page 1
Forum section: electronics / testgear

author: walterharriman
author_rank: Newbie
timestamp: January 15, 2014, 09:35:59 pm
content: As a teenage hobbyist, I was delighted to acquire my first 'scope for free through a HAM friend (I also got a slightly odd PSU, an analogue meter and a transistor decade oscillator, but never mind those). Here it is running normally the day after I got it - the weird lines aren't the scope, that's my camera, since the waveform was rolling when I took the image.Shortly after putting it into the cupboard with holes and ventilation in it that qualifies as a rack for me, the thing started acting up. The first time was when I was trying to trigger off a perfectly normal sine wave when testing an oscillator - as I adjusted the trigger level, there was a loud arc noise and for a split second, the trace jumped over to form a dot on the left side of the graticule. I promptly turned the scope off, but shortly afterwards had to leave the lab for the day and forgot entirely about what had happened. On switching the scope on again a couple of days later, without anything plugged in, it began to do the same thing again, getting faster, at which point I was pretty sure I was about to release the magic smoke and shut it off again. After being distracted from electronics for a month by a mixture of schoolwork and the horrific weather we have been having in the UK, I finally decided that I'd pop the cover on it today and see if any magic smoke was escaping - which brings me to the main part of this post.On removing the cover from the scope (and being occasioned by an extremely inconveniently placed grounding wire!), I was greeted by this sight.Firstly, just as an aside, the classic curved traces on the boards:but, far more disconcertingly, this label:and the insulator washers it refers to (both of those large caps have two, one on each leg). I decided to consult the forum for advice, as I am honestly not sure of the best way to approach beryllium oxide. Should I leave it be and just be extremely careful not to scratch or smash the insulators, or is it worth attempting to replace them with a modern alternative? I can provide further pictures if necessary, and I will resume trying to diagnose the scope once I've got this beryllia issue sorted out.

author: DmitryL
author_rank: Regular Contributor
timestamp: January 15, 2014, 09:43:19 pm
content: Quote from: walterharriman on January 15, 2014, 09:35:59 pm1. Don't eat berillium oxide washers, it may cause constipation.2. Don't grind them into a powder and sniff it; If you do it for long enough time, it may cause some lungs problems.

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 15, 2014, 10:35:05 pm
content: The BeO is definitely NOT in those capacitor standoffs. Those look like glass filled phenolic or similar.BeO is used where electrical insulation AND high thermal conductivity is required. There is no need for thermal conductivity on those standoff insulators.Check the insulating washers between power semiconductors and heatsinks. A washer that is thicker than the usual greased mica or silicone type, and made of a white ceramic material, is likely BeO.They pose no serious hazard unless broken into particles small enough to be inhaled. Unless you need to replace one of the components they are used on, I wouldn't disturb them.Be VERY careful around those exposed CRT socket pins, and the power supply circuitry in general. CRTs run on hazardous voltages.

author: sync
author_rank: Frequent Contributor
timestamp: January 16, 2014, 12:31:27 am
content: From the manual.for using Beryllia.

author: bxs
author_rank: Regular Contributor
timestamp: January 16, 2014, 01:20:04 am
content: Quote from: sync on January 16, 2014, 12:31:27 amFrom the image in thesyncpost:"Note: The insulating washers used in the mounting of power transistors on the rear of the heat sink flange at the rear are of beryllia which can be highly toxic (...)"What are the aspect of those washers? Are they like a white ceramic?EDIT:I need to read things a little better, seems thatN2IXKalready answered it, ups...Quote from: N2IXK on January 15, 2014, 10:35:05 pmSo, it's physically something like this?

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 16, 2014, 02:20:54 am
content: Yes, that certainly looks like a BeO washer to me.

author: c4757p
author_rank: Super Contributor
timestamp: January 16, 2014, 02:24:59 am
content: That could just as easily be alumina, though - I just installed an alumina washer no less than twenty minutes ago that looked exactly like that.

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 16, 2014, 02:39:27 am
content: Yes, Al2O3 looks pretty much the same. But the thermal conductivity of BeO is significantly better.http://www.makeitfrom.com/compare-materials/?A=Alumina-Aluminum-Oxide-Al2O3&B=Beryllia-Beryllium-Oxide-BeO

author: bxs
author_rank: Regular Contributor
timestamp: January 16, 2014, 03:38:13 am
content: @ N2IXK, c4757pThanks, just what I needed to know.A bit off -topic:I heard that the main dangerous in old stuff are mainly PCBs and Beryllium-Oxide. (Edit: also radiation...)For PCBs I have an idea in how old a device need to be to have them and how to identify them (at least I think...)For BeO I don't know very wheel, I know that in old stuff any hard white ceramic for things like valve bases, heat-sinks can be made of BeO; some power stuff like a power Transistor also can have BeO, some even have BeO inside their package; and for RF stuff BeO seems to be everywhere...But how old need a device to be to have BeO and no warning sticker?Seems that BeO was/is also use in thermal paste, do you know how old need a device to be to have BeO thermal paste?Man, so many dangers...Thanks

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 16, 2014, 04:01:23 am
content: As far as PCBs, suspect any oil-filled capacitor or transformer that isn't specifically marked "non-PCB". Specific tradenames to look for would include "Chlorinol", "Pyranol", "Dykanol", "Inerteen", "Hyvol", "Arochlor", or "Askarel". PCB fluids often have a faint chlorine odor.White ceramic valve bases are harmless steatite or similar porcelain. BeO is only used where heat needs to be carried from a hot surface to a heatsink, while maintaining electrical insulation. In valves, it is used as a "thermal link" between a metal anode (at high voltage) and a grounded cold plate, radiator, or heat sink. A few tubes (mostly exotic microwave stuff like large klystrons) incorporate BeO internal parts or RF windows.A little-known use of BeO was in very early fluorescent lamp phosphors, as well as phosphors used in early projection CRTs. These are particularly hazardous, because the phosphors are very fine powders, which get airborne once the tube is broken open.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 16, 2014, 06:37:51 am
content: I remember seeing a box containing an RF transistor with a BeO substrate, that had a printed warning "DO NOT DISPOSE OF".Huh. So what are you supposed to do with it?As I recall, the toxicity of BeO was discovered when there was a huge rise in cancers all around some factory that made BeO. It's apparently something will give you cancer for sure, with even incredibly amounts absorbed into the body. Typically by breathing it as dust. With the factory, people were getting cancers from the dust on worker's clothes being carried outside the factory.http://en.wikipedia.org/wiki/BerylliumI have an X-ray tube out of an X-ray fluorescence analyzer, that has a beryllium end window. You should see the safety warnings in the tube specs. Basically, never touch or clean the window. Under any circumstances.Anyway, BeO is a white or pinkish ceramic. Originally used as electrically insulating shims under power transistors, or the bodies of RF transistors and valves. Avoid handling.

author: walterharriman
author_rank: Newbie
timestamp: January 16, 2014, 08:31:21 am
content: Thanks so much for all the quick responses guys! I guess I should have known that it would be too easy if the label was near the things that actually contained the BeO... I've looked at my photos again (no time to get down to the lab now, it's just before school) and of the three power transistors I can see, only one has a visible insulator, which doesn't look very BeO to me... There are some small white washers around the legs of a couple of resistors, visible in this photo - will they be it?There also seems to be some white debris on the board, like corrosion of some sort. Hmmmm. Age? Or crystallised magic smoke?

author: lowimpedance
author_rank: Super Contributor
timestamp: January 16, 2014, 11:38:48 am
content: Quote from: walterharriman on January 16, 2014, 08:31:21 amThe 'beads' on the resistors are not BeO, just a ceramic standoff.Might be a good idea to remove the 'dust' (carefully outside with a brush). and make sure no components around it have been affected physically. Also check the power components still have sound solder joints.AS N2IXK said - do be careful, particularly of stored charge in the tube etc (it does have the 'OTHER' warning sticker too!)

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 16, 2014, 12:48:24 pm
content: The transistor on the right in the last pic looks to have a standard mica washer under it.The other 3 aren't as obvious, so check them carefully for washers that resemble the one above. It is always possible that the BeO washers were replaced previously, but the warning label wasn't removed.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 16, 2014, 02:06:54 pm
content: Speaking of Berrylium:http://www.theverge.com/2014/1/14/5307582/james-webb-space-telescope-NASAImages of the James Webb Telescope, soon to be Hubble's successor.So far, no one has dropped it.

author: electronics man
author_rank: Frequent Contributor
timestamp: January 16, 2014, 09:25:26 pm
content: I think it is best to wear gloves and a face mask when handling this stuff and do not handle it around food. The other word to say is if you are not sure if it is BeO or not then treat it as if it was BeO. Better safe than sorry.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 17, 2014, 01:46:08 am
content: Quote from: N2IXK on January 16, 2014, 12:48:24 pmOr that they were never fitted!---Sometimes Management go into panic mode & everything has to have a "warning" sticker.whether it is used in that particular unit or not!There seems to be an increasing trend to portray Electronics as a very hazardous occupation,somewhere between lion taming & GP racing,whereas you are more likely to meet your end from a heart attack,or any of the the other ailments common to sedentary occupations.If you want to be a thrillseeker,take up bungee jumping!Unless you take to the Beryllium with a grindstone,it can be handled with impunity---just wash your hands afterwards,as you would anyway.Some old equipment is alleged to use heatsinkcompoundcontaining beryllium.I have found some blue-green coloured stuff which I am a bit wary of,so maybe a few more precautions may be in order there.Some very old equipment,& automotive parts use cadmium plated screws--when it gets old the plating becomes powdery & may be a hazard.It doesn't get as much publicity as beryllium,though---probably because it doesn't have such a fancy name!Again,though,in most cases---just wash your hands!

author: electronics man
author_rank: Frequent Contributor
timestamp: January 17, 2014, 09:43:12 pm
content: What age of equipment contained BeO?

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 18, 2014, 04:38:38 am
content: 1940s to present.Warning labels from maybe late 60s onward....

author: SeanB
author_rank: Super Contributor
timestamp: January 18, 2014, 05:32:41 am
content: Microwve oven magnetrons may also contain Beryllia. If the ceramic end insulator is pink it is likely BeO. Just do not break it if you take it apart.

author: bxs
author_rank: Regular Contributor
timestamp: January 18, 2014, 01:18:31 pm
content: Quote from: N2IXK on January 18, 2014, 04:38:38 amThanks, now I can have an idea of the dates and since when Warning labels started being applied.Those figures also apply to beryllium in thermal paste/grease?

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 18, 2014, 03:59:45 pm
content: Quote from: SeanB on January 18, 2014, 05:32:41 amPink ceramic is likely alumina with a chromium impurity that provides the color (and increases strength). Chromium doped aluminum oxide in single crystal form is better known as the gemstone ruby. RCA/Burle and Svetlana ceramic power tubes used lots of this stuff. Perfectly harmless.Not sure how prevalent the use of BeO in heatsink grease was, or when/where it was likely to have been used. Would be harder to identify in that form, though.

author: bxs
author_rank: Regular Contributor
timestamp: January 18, 2014, 06:12:56 pm
content: Quote from: N2IXK on January 18, 2014, 03:59:45 pmI remembered of this video:watch from 21:50 to 23:30Seems that the change from Beryllium to Zinc Oxide in thermal paste was around 1992

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 18, 2014, 06:38:36 pm
content: I've got an old tube of heat sink grease from the '70s that is labeled as zinc oxide.Like BeO washers, I suspect the BeO grease was mainly used in high performance applications, where the considerable price premium was justifiable.Kind of surprising to see it used in a low-end scope like this Farnell, actually....