Marconi 2022C - Which component(s) contains Beryllium Oxide? - Page 1
Forum section: electronics / repair

author: nidlaX
author_rank: Frequent Contributor
timestamp: July 13, 2025, 09:08:16 am
content: I'm starting work on a 2022C and didn't realize until I opened the cover on AB1/1 that there's a BeO component inside. I thought the component would be under the can that has the warning stickers, but TR20 is actually in the middle of the board (Motorola MRF587, 8914 datecode).Wondering if anyone here knows for certain whether the component that contains BeO is in fact TR20, or could it be mis-marked somehow (doubtful, but I'm paranoid)? The only Motorola datasheet I've found for MRF587 is dated 1994 Rev 6 with no BeO warnings of any kind.

author: coppercone2
author_rank: Super Contributor
timestamp: July 13, 2025, 09:54:22 am
content: that's because its a solid piece of ceramic that won't do anything unless you start bashing it with a hammer and sniffing thatitsstable. This is a warning for people that might throw the PCB into a shredder for metals reclamation. Like a big shredder that pulverizes stuff for like burning and smeltingIts not a crumbly material that disintegrates over time. I think the beryllium model people seem to have is like a soft decomposing lime brick?if you take a rod of it and tap it on something it makes a metal like noise.For thermal reasons its sintered to maximum. The whole point is that it has good thermal conductivity. to have the best thermal conductivity you basically fire it to the maximum to get rid of as many voids as possible. Its sintered so hard it almost looks glazed.The biggest hazard is the dremel. You might be tempted to use a dremel to slightly grind certain ceramics to make them fit, because its difficult to replace heatsinks and stuff inside of a crowded chassis. If you don't do that you are fine.This material tends to cleave when you break it, meaning a extremely fine crack line, much like breaking glass. It should not powder easily. It should not have much residual stress in it, in case if you are wondering if it does what glass does, which it does not.As for thermal cycling, I found that with most engineering grade ceramics, if you say get it white hot, and cool it down too fast, too many times, it develops a invisible crack (which is visible when you heat it to red+ hot), and may eventually split or chip, into fairly large pieces.the stuff that gets 'nasty' is thermal insulation. That means puffy, but fortunately using beo as thermal insulation does not make any sense, because you want a LOW thermal conductivity, not a high one! BeO is more like a thermal SHUNTThermal insulation ceramics are the ones that get nasty, fall apart, etc.. because they are basically made to be as foam like as possible. That's why kilns are dirty. Unless you are getting red hot, ceramic insulators don't make sense anyway, save for maybe aerogel. Because something like polyisocyanutrate foam kills everything under maybe 100 degrees C and is cheap.

author: nidlaX
author_rank: Frequent Contributor
timestamp: July 13, 2025, 10:11:57 am
content: Thank you for the detailed reply! You reinforced most of my understanding of the properties and risks associated with the ceramic. Part of my increased caution is that I have no idea about the history of the device and any previous attempts at handling or repairing the component. Again, more paranoia than practical risk, but I really appreciate the info and guidance.

author: coppercone2
author_rank: Super Contributor
timestamp: July 16, 2025, 11:03:03 pm
content: And there is one sign you can look for, IMO its slightly brighter then alumina. Very slightly brighter. If you put them on top of each other the BeO might look a tiny bit whiter. If you deal with AlO2 alot and you notice a part that looks unusually bright, it could be it.For handling it, it feels more metallic then alumina. That is the best I can describe it. Alumina might feel like a very hard chalk, but the berylia will feel a tiny bit metallic (perhaps due to its much higher thermal conductivity). Even for a thin plate, it feels oddly metalic because of its thermal conductity.if it is more of a amber/grey color, then that is probably AlN.But I don't think I could reliably sort alumina and berylia by sight. The difference is so small that it feels like its in your head.But you can only do the tests on similar sized pieces if you touch it.Easy to tell difference between similar size AlN and Al2O3. Comparing a large Al2O3 sheet to a small BeO sheet.. both feel rather cold. I think its because of the larger sheet having more heat to distribute sideways.I have a rather large alumina block here, and it feels like a big chalk stick. I imagine if I had a big AlN block, it would feel like metal. BeO more so then that, but I don't think you will find one other then at Y12 or something