Persamaan Transistor D998 B778
Technical Report: D998 (NPN) and B778 (PNP) Transistor Pair
5. Important Substitution Guidelines
-
Check Supply Voltage: Original D998/B778 are rated for 160V (Vceo). If your amplifier runs on ±70V DC rails or less, you can safely use 140V-rated transistors like 2SC5200/2SA1943. If rails are ±75V to ±80V, choose 200V+ types (MJL4281A/4302A or 2SC3858/2SA1494).
-
Package Compatibility: The original TO-3P (also called TO-247 or TO-3PL) has the same pinout as modern TO-247/TO-264. Pinout: B-C-E (left to right when facing flat side with pins down). Most equivalents match this.
-
Heat Sinking: Equivalent transistors often have higher power ratings (e.g., 150W–230W vs 100W). This is safe, but ensure the mica insulator and thermal paste are properly applied. Persamaan Transistor D998 B778
-
hFE Matching: For audio quality, buy matched pairs or measure hFE. Original parts had hFE range 40–140. Modern equivalents (e.g., 2SC5200) are typically 55–160. Close matching between NPN and PNP reduces distortion.
-
Bias Adjustment: After replacement, always re-adjust the quiescent current (idle bias) per the amplifier’s service manual to prevent thermal runaway. Technical Report: D998 (NPN) and B778 (PNP) Transistor
Persamaan Transistor D998 dan B778: Panduan Teknis dan Aplikasi
6. Typical Applications
1. General Description
The 2SD998 and 2SB778 are a complementary pair of silicon epitaxial planar transistors designed specifically for high-power audio amplification. They are manufactured by Sanken Electric Co., Ltd. (often marked as D998 and B778).
They are commonly found in high-fidelity (Hi-Fi) stereo amplifiers, PA systems, and high-end car audio amplifiers from the 1990s–2000s (e.g., brands like Technics, Kenwood, JVC, Pioneer). Check Supply Voltage: Original D998/B778 are rated for
Langkah 3: Perhatikan Pembagian Kerja (Matched Pair)
Jika Anda membaca datasheet, hFE original D998 adalah R(55-110), O(70-140), Y(110-220). Untuk C5200, pilih yang kode O atau Y. Saran: Beli 5 pasang sekaligus, lalu ukur hFE dengan multimeter transistor. Pasangkan yang nilai hFE nya paling dekat (beda maksimal 5%).
Spesifikasi Teknis Utama:
| Parameter | Nilai | Satuan | | :--- | :--- | :--- | | Tegangan Kolektor-Emitor (Vceo) | 120 | Volt | | Arus Kolektor (Ic) | 10 (Maks 15) | Ampere | | Disipasi Daya (Pc) | 80 (dengan heatsink) | Watt | | Frekuensi Transisi (ft) | 30 | MHz | | Kemasan (Package) | TO-3P (Isolated) | - |
Karakteristik Penting:
- Gain (hFE): Rata-rata 55 hingga 180. Memiliki linearitas yang baik untuk audio.
- VCE(sat): Rendah, sehingga efisien untuk daya tinggi.
Karena Vceo hanya 120V, transistor ini sebenarnya dikategorikan sebagai transistor tegangan menengah, bukan tegangan tinggi. Ini penting karena jika Anda menggantinya dengan transistor tegangan terlalu tinggi (misal 250V) tanpa penyesuaian bias, suara bisa menjadi kasar.