The Brenell Mini 8 is an 8-track tape recorder designed for professional audio recording and playback. It consists of two main units: the tape deck with its associated record/replay electronics, and a separate Power Supply Unit (PSU). This two-unit design minimizes magnetic induction from the PSU's transformers and bias/erase oscillator, ensuring cleaner audio.
Important Technical Specifications:
- Tape Speed: Selectable between HI (15 inches/second or 38 cm/s) and LO (7½ inches/second or 19 cm/s).
- Reel Size: Accepts up to 10½ inch (260 mm) NAB reels.
- Input Impedance: 10K ohm, accepting unbalanced inputs up to 10K ohms impedance.
- Input Sensitivity: Adjustable from -10dBm to +20dBm for optimum record level.
- Output Impedance: Less than 100 Ohms, suitable for balanced or unbalanced loads of 600 ohms or greater.
- Output Level: Adjustable up to +10dBm for OVU.
- Fuses (240V. operation):
- Main fuse: 2.5 A (anti-surge)
- Deck power: 2.5 A (anti-surge)
- Electronics 40V. rail: 5 A (semi-delay protection)
- Fuses (110V. operation):
- Main fuse: 5 A (anti-surge)
- Deck power: 5 A (anti-surge)
- Electronics 40V. rail: 5 A (semi-delay protection)
- Record/Replay Delay: Approximately 0.15 seconds between line and replay signals due to head spacing (45 mm).
- Calibration Tape: BASF Calibration Tape No. 15 (or equivalent) for 15 ips tape speed, with equalization corresponding to 50 + 3,180 µs.
Function Description:
The Brenell Mini 8 is designed for multi-track recording and playback. It features eight input and eight output single-pole jacks on the rear panel, corresponding to channels one to eight on the tape. The unit includes a three-head assembly (erase, record/sync replay, and replay) protected by a removable cover. A manually operated replay head shield is provided to minimize hum induction during mixdown operations.
The tape path includes a reel carrier with threaded hubs for securing reels, a tape tension arm that maintains steady tension and operates an auto-stop mechanism, a pinch roller that holds the tape against the capstan during PLAY, and a motion sensing roller. The motion sensing roller detects tape direction and rate, feeding data to logic elements for deck control and providing a real-time output for the tape counter.
Usage Features:
- Installation: The PSU connects to the tape recorder via a 15-way plug and socket. The tape recorder can be mounted vertically or horizontally, requiring adequate space at the rear for ventilation.
- Power: A RED indicator on the PSU front panel (or on the tape recorder itself for later models) lights when power is available/switched on.
- Tape Loading/Unloading:
- Reel retainers are unscrewed anti-clockwise.
- A full reel is placed on the left carrier, an empty reel on the right.
- Reel adjusting shims (0.7 mm thick) are provided to compensate for different reel thicknesses.
- Tape path: over tension arm, across heads (between mu-metal shield and replay head), between pinch roller and capstan, around motion-sensing roller, onto take-up reel.
- Unloading is achieved by pressing REWIND or WIND, which winds all tape onto one reel and operates the auto-stop.
- Controls and Indicators:
- Speed Selector: Toggle switch for HI (15 ips) or LO (7½ ips). Should preferably only be changed when the capstan is stopped.
- Deck Mode Selector Switches: Five colored push-buttons:
- REWIND (BLUE): Tape fast rewind.
- WIND (BLUE): Tape fast wind.
- PLAY (GREEN): Tape replay, or with REC for recording.
- STOP (YELLOW): Stops tape movement.
- REC (RED): Used with PLAY to select record mode.
- Channel Units: Each channel has preset controls for alignment, but normal user controls include:
- Record (ON/OFF): Selects record mode for the channel. A flashing red REC indicator means standby; continuous illumination means recording is active.
- Line-in-Level: Rotary control for input level.
- Line-out-Level: Rotary control for overall output level.
- Line-out-Selector: Three-position switch for monitoring:
- SYNC: Synchronized output from the record head (or input signal in record mode).
- LINE: Input signal available at the line-output.
- REPLAY: Signal from the replay head.
- VU Meters: Eight standard VU meters provide visual indication of input, sync replay, or replay levels, switched automatically by the line, sync, replay selectors.
- Recording:
- Adjust line-in level so modulation peaks do not exceed OVU (red area).
- Set channel record switch to ON.
- Start recorder by pressing PLAY and RECORD simultaneously.
- Input signal can be monitored via the line-out switch in the LINE position; recorded signal in the REPLAY position.
- Recording can be stopped by pressing STOP or switching the channel record switch to OFF.
- "Dropping in" (starting recording on an already playing tape) is possible by selecting RECORD ON on the appropriate channel(s) after the deck is in record mode. This avoids wow and flutter during start-up.
- Playback:
- Load tape.
- Select tracks by setting record switch(es) to OFF and line-out switch to REPLAY.
- Press PLAY.
- Replay signal is available at channel jacks, with level adjustable via the output level control.
- Remote Control and Vari-speed:
- Remote Counter: Digital tape counter driven by a photo-electric sensor, providing real-time indication (minutes and hundredths of minutes) at 15 ips (half real-time at 7½ ips). Connects via a multi-pin socket. Includes a zero setting button.
- Remote Control Unit: Available for interfacing all deck and channel functions via the multi-pin socket.
- Vari-speed: A remote drive socket allows connection of a 240V. signal at varying frequency to control capstan speed.
Maintenance Features:
- Basic Maintenance: Bearings are lubricated for life. User maintenance is limited to keeping the tape path clean and demagnetized.
- Cleaning: Use proprietary head cleaning fluid. Avoid hard or metallic tools to prevent stray magnetism and scratches. Use soft cloths or cotton-tipped sticks.
- De-Magnetizing: Regularly demagnetize the tape path (guides, heads, lifters, capstan, motion sensing roller). Never demagnetize while the machine is switched on.
- Fault Finding (User Checks):
- Check connectors and fuses if no power.
- For single channel failure, check input/output cables/jacks. An unused channel can be substituted.
- If recording fails on all channels, check bias/erase oscillator connection in the PSU.
- Mechanical Fault Finding:
- Lack of capstan drive (other functions O.K.): Check drive belts.
- Excessive wow and flutter: One drive belt broken.
- Slippage or running slow: Pinch roller pressure too low or broken drive belt.
- Relay Failure: All deck relays are 430-600 ohm 4 pole change-over. Record-on relay is miniature, low profile 24V. D.C. 2 pole change-over. Line, sync, replay relay are ITT (MZ).
- Channel Module Removal/Replacement:
- Removal: Undo two screws, insert screwdriver under top edge, gently ease out until edge connectors release.
- Replacement: Engage top and bottom edges in guides, slide home, replace screws. Alignment should be checked.
- Alignment Procedures (Competent Engineer Only):
- Preparation: Requires AC Millivoltmeter (e.g., Levell TM3B), Audio Signal Generator (e.g., Levell 200DM), and calibration tape (BASF 38/15). Heads, guides, capstan, and tools must be demagnetized. Head cover (3.3) may need removal. Calibration tape is for 15 ips only; ensure RECORD is OFF on all channels to prevent accidental erasure.
- Adjustments:
- Replay Gain and Sync Gain
- Record Head Azimuth
- Replay Head Azimuth
- Record Head Rotation
- Replay Head Rotation
- Replay Frequency Response Top Adjustment
- Record Bias Adjustment (most frequent adjustment for different tapes)
- Record/Replay Top Frequency Adjustment
- Record Level Adjustment
- Pinch Wheel 'Lock On' Adjustment (Appendix C): Ensures correct pressure between pinch wheel and capstan for constant tape speed. Involves adjusting the pinch solenoid plunger's 'Spring Tension Travel' to approximately 1.5 mm.
- Drive Belt Change Procedure (Appendix D): Detailed instructions for replacing drive belts.
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