What are these?

[Andrew Holme]

Does anyone recognise these:
http://www.holmea.demon.co.uk/Misc/0001.jpg

This is the inside of one:
http://www.holmea.demon.co.uk/Misc/0002.jpg

Some of them have tuning-slugs. I picked them up in a box of assorted junk
at a radio rally.

The markings are two letters (AA, PA, PM, FD, VR ... etc) followed by three
digits always beginning with an 8 i.e. 8xx, sometimes with a siffix e.g.
803a. The date codes are 1979 or 1980.

I'm a little concerned that the white substrate material might be BeO -
especially after prising one open (!)

 

[John Woodgate]

I read in sci.electronics.design that Andrew Holme <andrew@nospam.com>
wrote (in <de9rgm$oqi$1$8300dec7@news.demon.co.uk&gt about 'What are
these?', on Sun, 21 Aug 2005:

I'm a little concerned that the white substrate material might be BeO -
especially after prising one open (!)

If it's solid, it won't matter too much health-wise, as long as you wash
your hands, any more than if they were emeralds. But you will have a job
disposing of them legally.
--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Pooh Bear]

Andrew Holme wrote:

Does anyone recognise these:
http://www.holmea.demon.co.uk/Misc/0001.jpg

This is the inside of one:
http://www.holmea.demon.co.uk/Misc/0002.jpg

Some of them have tuning-slugs. I picked them up in a box of assorted junk
at a radio rally.

The markings are two letters (AA, PA, PM, FD, VR ... etc) followed by three
digits always beginning with an 8 i.e. 8xx, sometimes with a siffix e.g.
803a. The date codes are 1979 or 1980.

I'm a little concerned that the white substrate material might be BeO -
especially after prising one open (!)

Probably just alumina.

Graham

 

[Spehro Pefhany]

On Sun, 21 Aug 2005 13:15:58 +0100, the renowned "Andrew Holme"
<andrew@nospam.com> wrote:

Does anyone recognise these:
http://www.holmea.demon.co.uk/Misc/0001.jpg

This is the inside of one:
http://www.holmea.demon.co.uk/Misc/0002.jpg

Some of them have tuning-slugs. I picked them up in a box of assorted junk
at a radio rally.

The markings are two letters (AA, PA, PM, FD, VR ... etc) followed by three
digits always beginning with an 8 i.e. 8xx, sometimes with a siffix e.g.
803a. The date codes are 1979 or 1980.

I'm a little concerned that the white substrate material might be BeO -
especially after prising one open (!)

Looks like an unremarkable hybrid circuit. Very unlikely to be BeO, as
someone else said, most likely plain old alumina.

They used alumina rather than, say, FR4, partly because it will
withstand the firing temperatures for the screened-on resistors you
see. Unless there was some heat dissipation requirement, that circuit
would probably be built today on a bit of FR4 with chip resistors.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com