Olympus BH-2 BHTU Manuel - Page 14

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Power Transistor

Power transistor Q101 is a Toshiba 2SD867 NPN power transistor in the old TO‐3 metal package (see Figure 15). This

part, although obsolete, can still occasionally be found, but expect to pay $20 or more for it when you find it. If the

2SD867 cannot be found, this part can be replaced with the STMicroelectronics BUX10 part, which is the same package

style and is also obsolete. The NTE36 part in the TO‐3P insulated case is a good substitute that is available from Allied

Electronics and from Amazon.

Whichever approach is taken, the replacement transistor must be installed using suitable mounting hardware which

provides electrical isolation of the collector tab from the equipment chassis, and thermal paste must be used on both

sides of the insulator to enhance thermal conduction. If none of the parts listed above can be found, look for an NPN

part with a collector current rating of at least 15A, a collector‐to‐emitter voltage rating of at least 100V, and a current

gain of at least 40, in a suitable power package.

Figure 15 ‐ Power Transistor Mounted to BHT/BHTU Electrical Base (100/115V Version)

AC Inlet Jack

For safety, always replace the AC inlet jack with an equivalent part, when available (see Figure 16). Make sure that the

chassis‐bonding screw for the ground (middle) terminal of the jack is present and secure and that the grounding wire is

undamaged before operating the equipment. This connection keeps the chassis at a safe potential in the event of any

electrical faults within the equipment.

If a suitable replacement jack cannot be located, a filler plate could be fabricated to take the place of the AC inlet jack,

with a suitable hole drilled to allow an AC line cord to be installed with a strain‐relief grommet. If this approach is

chosen, be sure to securely bond the ground conductor of the power cord to the unit chassis to maintain equipment

safety.

Olympus BH‐2 (BHT/BHTU) Electronics

Revision 2

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