Olympus BH-2 BHT - Main Board Replacement

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OlympusBH‐2(BHT/BHTU)Electronics   Revision2    Page13of24
MainBoard
A replacement for the UYPC48 main printed circuit board (see Figure 13) is rarely needed, since the circuitry on this
boardisquitesimpleandcanusuallyberepairedwhennecessary.Suitablereplacementsformostcomponentscanbe
readilyfound.The5‐LEDmodulewouldbethehardestpartto
find,butcouldbereplacedwithfiveseparaterectangular
LEDsifnecessary.TheuPC324C op‐ampcanbereplacedwiththeLM324C,intheDIPpackage.TransistorsQ201and
Q202maybereplacedwith2N3906PNPdevices(besuretoaccountfordifferencesinpinoutwheninstallingtheseas
replacements).Diode
D201canbereplacedwitha1N4002or1N4004rectifierdiode, anddiodesD202,D203,andD204
canbereplaced with 1N916 or 1N4148 small‐signal diodes.The 0.1Ω5Wpowerresistor,R201,runs very hotduring
normaloperation,andbecauseofthisthesolderjointscansometimesgobad.
ResolderingtheleadsofR201maybe
enough to fix an inoperative lamp dimmer. Resistor R201 can be replaced with a Vishay CP0005R1000JE14 part,
availablefromMouserElectronics.
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Figure13–OlympusUYPC48MainBoardMountedtoBHT/BHTUElectricalBase(100/115VVersion)
Intherarecasethatthemainboard
isdamagedbeyondrepair,anaftermarketreplacementfortheOlympusUYPC48
mainboardisavailablefromJ.C.RitcheyCompany,LLC(seeFigure14).Thisboard,whichisadrop‐inreplacementfor
the original Olympus board, comes complete with a replacement power transistor and the necessary transistor
mountinginsulator.No
solderingisrequiredforthisoptionifonly thecircuitboardneedstobereplaced,butsoldering
isrequiredifthepowertransistoristo be replaced atthesametime.This looks to be a faithful repr oduction of the
originalOlympusboardandshouldperformwell.
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Figure14–
BHT/BHTUMainBoardReplacementKitfromJ.C.RitcheyCompany(photocourtesyJamesRitchey)