----- Original Message -----
From: "Nils Petter Pedersen" <la7sl@online.no>
To: <amps@contesting.com>
Sent: Saturday, November 17, 2007 3:47 PM
Subject: [Amps] more dangers in our shack
> While I am at it... there are more dangers in our shack:
> Apart from the more obvious danger of electromagnetic overexposure
> using our 3cx 15 000's and the likes...:-)
> A lot of power tubes and other devices contain Berryllium oxide.
> I have seen amps for the ham market that used conduction cooling
> by means of big blocks of Berryllium oxide (BeO) making thermal
> connectors to a back panel heatsink.
Heath SB-230 and a Henry VHF amp come to mind that use the 8873.
Also some Motorola VHF FM amps that use a conduction cooled 4CX250.
And GE VHF/UHF repeaters using the 8072.
I have also seen a fellow ham
> grinding and sanding these blocks to make a tight fit..
Dumb and Dumber!
> That process left a cover of fine dust on his workbench. He blew that
> away using an air hose....
> Well... I evacuated that room immediately and left him alone with the
> problem..
> Here is what I told him BEFORE he started on his project :
> Beryllium oxide (Beryllia):
>
> BeO is most often used as an electronic substrate, exploiting its high
> thermal conductivity and good electrical resistivity to give an effective
> heat sink. The material is found particularly in high power devices or
> high density electronic circuits for high speed computers.
>
>
> Extremely toxic by inhalation and ingestion. Typical LD50s for beryllium
> compounds are between 0.5 and 5 mg kg-1. Probable human carcinogen.
> Serious respiratory irritant. May be harmful by skin contact.
>
> Use only under properly controlled conditions. Avoid breathing dust or
> powder. Use safety glasses, gloves, good ventilation. Treat as a probable
> carcinogen. Prepare a full risk assessment before starting work.
What you neglected to mention is that inhalation of the dust is often fatal.
Carl
KM1H
>
> Have a nice weekend :-)
> Peter
> LA7SL
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