Olympus BH-2 BHT, Manual

Page: 13 / 24

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 0.1 Ω 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.
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 reproduction of the
original Olympus board and should perform well.
Figure 14 – BHT/BHTU Main Board Replacement Kit from J.C. Ritchey Company (photo courtesy James Ritchey)