⚙️ FOSTEX G16
16‑track · 1/2" tape · analog multitrack · Dolby C/S versions
Field‑collected data from technician forums and service manual excerpts. Two main variants: early Dolby C (cards with daughterboard) and later Dolby S (single‑chip cards PN 8251897).
Common complaint & field‑issue analysis
🔹 Erase failure (all tracks)
Insufficient erasure (should be ≥70dB) usually caused by low erase current. Measure at TP‑6: spec 85mVp‑p (30mV rms) at peak core adjustment. If voltage can't reach spec, suspect main erase/bias PCB or power supply [citation:2].
🔸 Intermittent channels / crackling
Symptoms: level drops, noise, meter issues. Problem moves with card → bad SMD electrolytics or cracked solder joints at edge connector. G16 with Dolby S cards (PN 8251897) have 36 electrolytics per channel; all must be replaced [citation:3][citation:6].
🧪 Motor driver confusion (schematics errors)
Service manual sometimes mislabels motor outputs. Users report chasing wrong circuit because "motor outputs labeled opposite on the schematic" [citation:1]. Always verify by tracing; transistors (2SD1047) fail in motor drive section.
🧪 Input normalling (1‑8 mirror to 9‑16)
Factory configuration: inputs 1‑8 are normalled to 9‑16. Plugging any RCA into channels 9‑16 breaks the normalling and disconnects the corresponding lower channel. This is normal, not a fault [citation:10].
Mechanical & transport system
TAPE LIFTER ADJUST
critical for head contact
Lifter must fully retract after FF/rewind; if it stays slightly engaged, tape‑to‑head contact is reduced, causing poor erase and weak record/playback [citation:2]. Check for mechanical binding or solenoid issues.
TENSION ROLLER HEIGHT Lateral tape motion should be observed between FF and RW; friction noise indicates misalignment. Adjust screws per service manual section (often loose from factory) [citation:4].
Calibration & alignment data
🎚️ Reference level:Align to MRL tape (e.g., 31J329 @ 320 nWb/m) for 0 VU = -10dBV [citation:8].
📼 Erase current adj:Adjust core T‑1 for peak at TP‑6, then ERASE LVL (R207) for 85mVp‑p [citation:2].
🎛️ Bias procedure:Find peak with BIAS ADJUST, then increase bias until 10kHz drops 3‑4dB from peak (for +6 tape) [citation:8].
🧲 Test points:Use TP‑6 for ground — never use TP‑5 (erase current test point) as ground reference [citation:6].
⚡ Daisy‑chain recording:Signal into ch1 routes to ch1‑8 automatically; arming all tracks records same tone across all 16 at once [citation:6].
Tape selection & compatibility
Original formulation: Ampex 456 (equivalent to RMGI SM911). Using modern high‑output tapes like SM900 or ATR requires careful recalibration [citation:4].
SM900 warning: Needs significantly lower bias than 456 — trimpot ranges are wide but adjustment is tedious. Erase current can remain at nominal spec [citation:4]. Old Ampex/Quantegy tapes may shed sticky residue; SM911 recommended for reliability [citation:4].
Speed: 15 ips only, 1/2" tape width.
Parts sourcing & service notes
🔧 Capacitor plague: Dolby S cards (PN 8251897) contain 36 SMD electrolytics per card. G16 total: 16 cards × 36 = 576 capacitors [citation:3]. Early Dolby C cards have fewer, but still need recap.
📘 Service manuals: Dolby C version available via miroslav's scan (link in forums). Dolby S manual covers G16S/G24S [citation:2][citation:3].
⚡ Cap replacement guide: Use bi‑polar electrolytics for audio path (Panasonic ECA series). Sub‑µF values (0.1, 0.15, 0.22, 0.47) best as WIMA film (polypropylene). See table below for 8251897 card [citation:3].
🎛️ R/P card capacitor guide (PN 8251897 — Dolby S)
Per‑card count: 36 electrolytics · G16S total: 576 caps · Use bi‑polar/film types as noted.
| Designator | Value | Designator | Value | Designator | Value |
|---|
| C12 | 10µF 16V | C39 | 1µF 50V | C74 | 10µF 16V |
| C13 | 10µF 16V | C43 | 0.1µF 50V | C75 | 10µF 16V |
| C16 | 10µF 16V | C46 | 0.1µF 50V | C77 | 10µF 16V |
| C17 | 10µF 16V | C48 | 10µF 16V | C80 | 0.15µF 50V |
| C18 | 10µF 16V | C52 | 0.1µF 50V | C81 | 10µF 16V (yellow) |
| C21 | 10µF 16V | C56 | 1µF 50V | C83 | 10µF 16V |
| C24 | 4.7µF 25V | C68 | 0.47µF 50V | C84 | 10µF 16V |
| C29 | 0.22µF 50V | C72 | 10µF 16V | C86 | 10µF 16V |
| C33 | 0.22µF 50V | C73 | 10µF 16V | C87 | 0.47µF 50V |
| | | | C89,91,92,97,105 | 1µF 50V |
C81 is a pre‑installed radial electrolytic (yellow). C24/C99/C107 are 4.7µF/25V. Values verified by multiple techs [citation:3]. Always verify against your card revision.
Synchronizer option (Model 8330)
📡 Function:Installs inside G16; adds LTC generation, 2x LTC readers, MIDI interface [citation:9].
🎛️ 2nd mode commands:2nd [9][0] sync on/off; 2nd [2][0] lock mode; 2nd [1][4] slave park area [citation:9].
⚙️ Chase/lock:After learning tach pulse rate, G16 can chase LTC from external ATR/VTR [citation:9].
Bias adjustment tips
⚠️ DUAL PEAK PHENOMENON Some G16s exhibit two peaks when sweeping BIAS ADJUST. Use the first peak (lower inductance) and then increase bias to drop 10kHz by 3‑4dB for +6 tape like SM911 [citation:8].
BIAS LEVEL pot After setting BIAS ADJUST (multi‑turn), use BIAS LEVEL to achieve desired overbias. Fully clockwise = minimum bias; counter‑clockwise increases bias [citation:8].
Safety & service notes
⚠️ high voltages, sensitive Dolby chips
Dolby S chips (Sony CXA14150/14160) are unobtainable; if dead, card loses NR. Handle cards carefully to avoid static discharge [citation:6].
🔒 Power supply caps also age — check rails. Motor driver transistors (2SD1047) known to fail; verify by swapping with known‑good channel [citation:1].
📏 Erasure spec: ≥70dB down; if not met, increase erase current ~10% or check mechanical tape contact [citation:2].
Key specifications
📻 Tracks:16 tracks on 1/2" tape
🎛️ Speed:15 ips (38 cm/sec)
📏 Reel size:10.5" or 12" (NAB)
🔌 I/O:16x RCA in/out, punch jacks, remote port
🎤 Noise reduction:Dolby C (early) or Dolby S (later cards)
📐 Dimensions:19" rack mount, deep chassis
* Capacitor counts approximate; always verify card revision. Donor machines are best source for spare mechanics and Dolby S cards.
