Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!portal!cup.portal.com!ISW
From: ISW@cup.portal.com (Isaac S Wingfield)
Newsgroups: sci.electronics
Subject: Re: Whatizzit?  ("Battery Booster")
Message-ID: <17076@cup.portal.com>
Date: 12 Apr 89 20:00:43 GMT
References: <27792@cci632.UUCP>
Distribution: na
Organization: The Portal System (TM)
Lines: 10

Your mysterious "brass disk" is a single junction Selenium
rectifier (if it's still any good). The reason you see AC under
no load is because those things had, by today's standards, terrible
reverse leakage.

Check out the waveform under load; if it rectifies, it's OK.
IF IT SMELLS LIKE ROTTEN EGGS, LOOK OUT. Selenium sulfide (I think)
is toxic.

Regards, Isaac     isw@cup.portal.com