It is not common for using a rheostat for regulating the lamp output, the
current is too high. A 20W bulb at 6V means over 3Amp. I have an olympus
microscope lamp transformer, the secondary (output) contains a winding with
variable tapping point so that you can adjust the output from 0-12V. I
believe you better search for a similar used one from ebay, in your case you
just need one up to 6V.
C.H.Ling
----- Original Message -----
From: "Charles Geilfuss" <charles.geilfuss@xxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Saturday, November 22, 2008 12:58 AM
Subject: Re: [OM] [OT] Electrical Part Help
> Frank,
> The one in the Wiki photo is *very* similar to the one in my scope. I
> tested mine still wired in place. The line current goes through a box that
> allows adjustment for different wall voltage (220/110) then through what
> looks to be a transformer, then to the rheostat which is in series with
> the
> bulb.
>
> Charlie
>
> On Fri, Nov 21, 2008 at 11:23 AM, Frank van Lindert
> <Frank@xxxxxxxxxxxxx>wrote:
>
>> Charlie,
>>
>> It is a bit weird. Normally the resistance of a rheostat is zero ohms
>> when the wiper is to one of the ends of the wire...
>>
>> Is the rheostat connected in series with the lightbulb or in series
>> with the wall outlet (and the primary coil of the transformer (if
>> there is any)?
>>
>> And did you disconnect the existing wiring when you took the
>> measurement?
>>
>> BTW, this is exactly what the rheostat in my own contraption I
>> described yesterday looks like:
>> http://en.wikipedia.org/wiki/Image:Pot1.jpg
>>
>> Frank van Lindert
>> Utrecht NL.
>>
>> Fri, 21 Nov 2008 09:46:38 -0500, "Charles Geilfuss"
>> <charles.geilfuss@xxxxxxxxx> wrote:
>>
>> >Greetings,
>> > Alright I have a little more infomation about my microscope rheostat:
>> > Firstly to correct my bogus information, it controls a 6 volt, 20
>> Watt
>> >halogen bulb.
>> >
>> > Secondly, I removed the bottom and put a multimeter on the two leads
>> >going into the body of the rheostat. I get no reading unless I set the
>> >multimeter to the 200 ohm range. At the rheostat's lowest range I get a
>> >reading of 0.3 and at the highest range a reading of 0.6. So if I'm
>> >using
>> my
>> >4th grade math correctly, the range of the rheostat is 60 ohms to 120
>> ohms.
>> >Do these figures make sense to those of you out there who know what you
>> are
>> >doing?
>> >
>> >Thanks,
>> >Charlie
>> >
>> >PS Boris I have taken some photos of the part and will e-mail to you
>> >off-List.
>> >
>> >On Wed, Nov 19, 2008 at 1:13 PM, Charles Geilfuss <
>> >charles.geilfuss@xxxxxxxxx> wrote:
>> >
>> >> Greetings All,
>> >> I know there are a few people on the List knowledgable about all
>> things
>> >> electrical, so I am hoping I can get some advice. I have a 15 year old
>> Leitz
>> >> Laborlux S microscope that I use daily. The rheostat (potentiometer)
>> >> controling the light source is going bad. The light will flicker and
>> does
>> >> not adjust smothly in some of its range. Visual inspection of the part
>> shows
>> >> wear on the surface of the coil. Cleaning with De-Oxit did not help.
>> >> I'm
>> >> planning to replace the part but Leitz no longer carries parts for
>> >> this
>> >> model and my efforts to find an original part have been fruitless.
>> >> There
>> are
>> >> plenty of potentiometers available form electrical parts companies,
>> >> but
>> how
>> >> do I determine what specifications I need. The scope uses a 6 Watt, 20
>> Volt
>> >> bulb and of course plugs into a 110 Volt wall outlet. Any advice?
>> >>
>> >> Thanks,
>> >> Charlie
>> >>
>> --
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