General > General Technical Chat
Magnetron insulators
(1/4) > >>
antenna:
I know this has been gone over a bunch of times but every thread warns me that it is an old thread, so starting new.

I remember hearing somewhere that its the red ceramic that is dangerous, then I heard they don't use beryllium anymore. Then, somewhere else, I read the white ceramic was dangerous too (and wikipedia shows it to be white), which confused me always hearing the red kind was bad.  The magnetron I took apart has both red and white ceramic. I would like to cut it open and see the cavities inside and how it failed so I am hoping someone can tell me which end is safest to use tools on.  Are both ends made of beryllium oxide?  Perhaps it is not worth looking inside...

Thanks!
T3sl4co1l:
AFAIK red is always chrome-tinted alumina, and white can be either (alumina or beryllia).

Only beryllia is toxic, and only when fractured or ground -- it's the dust.

Find a datasheet for it?

Anyway, you're cutting into metal right?  Just don't break the ceramics, you're fine.

Tim
richard.cs:
I did read somewhere that some beryllia is/was tinted red as an indicator/warning, but it was probably just on a forum somewhere. Certainly all the beryllia I have is white. In big pieces like a magnetron you can probably tell by thermal conductivity, it's a lot more conductive than alumina and should feel cool to the touch like a piece of metal.

If you have any doubts, cut the metal not the ceramic as Tim suggests.
antenna:
Thank you for the replies. I wonder how far into the metal the ceramics go, but regardless, I will cut into the larger cavity portion near one end and avoid the narrow sections that may contain the ceramic.  When the microwave failed, I tested the filament for continuity and for continuity between that and ground. There was still continuity between the filament connections, but also to ground. I expected that a failure would involve the filament breaking as I assumed it would be too heavy to simply stretch and short to ground, but that's the story my meter tells and the reason for my curiosity.  I will see if the thermal conductivity can provide a clue as to the materials, thanks again!

Gyro:

--- Quote ---I wonder how far into the metal the ceramics go, but regardless, I will cut into the larger cavity portion near one end and avoid the narrow sections that may contain the ceramic.
--- End quote ---

As a guide, here's my failed Panasonic magnetron (cracked magnet and anode structure melting)... https://www.eevblog.com/forum/chat/microwave-oven-pwm-frequency/msg3137762/#msg3137762 (See the image attachment)

First you need to pull off the sheet metal anode cap - it pulls off with pliers. Then saw through the copper pinch seal that you will find underneath. This breaks the vacuum (tiny hiss) and frees up the anode connection rod which is crimped in with it.

The easiest place to cut is between the top of the copper anode and the top steel plate - there is normally a groove. Rotate it while cutting to avoid damaging the internal structure and avoid excessive clamping pressure - the copper cylinder may look very solid but it is soft and easily distorts if squeezed too hard.

There is no Beryllium in either ceramic tube (as has been discussed at length in previous threads), but there is no need to cut or clamp them anyway and shattering ceramic won't do your eyes any good regardless!

Any device containing Beryllium will have a prominent warning label.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod