How to test with a multimeter (diode mode):
| Test | Red Probe | Black Probe | Expected Reading | | :--- | :--- | :--- | :--- | | NPN (D998) B-E | Base | Emitter | 0.5–0.7V | | NPN (D998) B-C | Base | Collector | 0.5–0.7V | | PNP (B778) E-B | Emitter | Base | 0.5–0.7V | | PNP (B778) C-B | Collector | Base | 0.5–0.7V |
Common failures:
Lepaskan kedua transistor final (driver dan final) dari heatsink. Bersihkan pasta thermal lama. Persamaan Transistor D998 B778
These values determine the performance of the transistor in a circuit.
Most D998 and B778 transistors use the TO-220 package with the following pinout (looking at the front face):
(Note: Always verify the datasheet of the specific manufacturer, as Japanese transistor pinouts can sometimes vary, though B-C-E is standard for this series). How to test with a multimeter (diode mode):
Kasus: Amplifier 400W Polytron, output DC offset +45V. D998 dan B778 short semua. Tindakan:
Sebelum mencari pengganti, Anda harus memahami karakteristik asli komponen ini. D998 dan B778 adalah sepasang transistor bipolar (BJT) komplementer.
The 2SD998 and 2SB778 are a complementary pair of bipolar junction transistors (BJTs). They are designed primarily for audio frequency power amplifier applications and general-purpose switching. Transition Frequency ($f_T$):
These transistors were widely used in older audio equipment (stereo amplifiers, receivers) and are now often found in electronics repair scenarios. While they are robust, they are considered "legacy" components, meaning modern equivalents are often used for replacements.
Fakta: Meskipun lebih bagus (MT-200 casing besar), ukuran fisiknya lebih besar. Kemungkinan tidak muat di PCB asli D998/B778. Jika ingin upgrade, Anda harus mengebor ulang lubang PCB dan mengganti mika isolator.