Olympus BH-2 BHT - Common Problems with BHT;BHTU Electronics; Lamp House Contact Issues; Intensity Control Problems; Obtaining Replacement Components

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OlympusBH‐2(BHT/BHTU)Electronics   Revision2    Page9of24
CommonProblemswiththeBHT/BHTUElectronics
The electronics in the BHT/BHTU microscopes have proven to be remarkably reliable over the years, but with heavy
usage,failure s  do occur.The mostlikely problems  in the electronics will be bad orintermittentcontacts in the lamp
houseanderraticlampintensityduetodust,dirt,andoxidationwithinthe
intensitycontrol.
Wornoroxidizedcontactsinthesocketinthelamphousewillcausethehalogenbulbtonotilluminate,toflicker,orto
illuminate only intermittently.If a replacement lamp house is not available, the troublesome lamp socket may be
replacedwithanewone,asdescribedlater
inthisdocument.Itmayalsobepossibletoeffectatemporaryrepairby
disassemblingtheexistinglampsocketandcleaningtheoxidizedcontactswithemerypaper,butthisshouldbeviewed
asatemporaryfixonly.
Dust, dirt, and oxidation within the intensity  control can cause erratic lamp intensity as
 the control slider is moved
throughout its adjustment range.This can usually be corrected  by spraying a short blast of volume control/contact
cleaner(afterunpluggingtheAClinecord)intotheintensitycontrolandmovingthesliderthroughoutitsfullrangeof
motionafewtimestodistributethecleaner
(seeAppendix1ofthisdocumentforasuggestedcleaner).Exercisecaution
whensprayingthe cleaner into the control so as tominimize overspray and blow‐backonto nearby components.Be
sure to allow the contact cleaner sufficient time to evaporate out of the control before re‐applying power to the
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electricalbase.
ObtainingReplacementComponents
TheBHT/BHTUmicroscopesarenolongersupportedbyOlympus,andwithfewexceptions,factoryreplacementparts
arenotavailable.Someelectri calparts(orsuitablesubstitutes)areavailablefromthirdpartysources,andtheseparts
arelistedinAppendix1ofthisdocument,alongwithsourcesandpricing.
TheBHT/BHTUmicroscopeswere
verypopularintheirday,andusedstandsandtheirvariousbitsandpiecesfrequently
showupforsaleonebay.Ifnecessary,replacementelectricalcomponentscanbesalvagedfromaspareelectricalbase.
Ifexactreplacementscannotbefound,makesurethatanysubstitu tepartschosenforrepairshave
suitableelectrical
andmechanicalspecificationsandthattheyareinstalledinsuchawaythatitisnotpossiblefortheoperatortocontact
anylivevoltagepointswhileusingthemicroscope.
PowerTransformer
Thegoodnewshereisthatthepowertransformer(showninFigure7)rarelyfails.Thebadnewsisitmaybedifficultto 
locateasuitablesubstituteforitifiteverdoesfail,duetotheuniqueformfactorwhichallowsittofitintothebaseof
theBHT/BHTUstand.Ifasuitablesubstitutecannotbefoundforthetransformer,this maybeagoodtimetostarton
thatLEDconversionproject,whilelookingforanotherelectricalbase.
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Figure7–PowerTransformerMountedtoBHT/BHTUElectricalBase(100/115VVersion)