Studer A807

Overview

The Studer A807, produced from approximately 1985 to 1993, represents the final evolution of Studer's professional analog tape recorders . Designed for broadcast and studio applications, the A807 features microprocessor-controlled transport, sophisticated tape tension control, and excellent audio performance in a compact package . It was available in various configurations including 1/4" stereo, 1/2" two-track, and even multi-track versions .

The A807 was designed as a more affordable alternative to the larger A80 and A820, while maintaining Studer's legendary build quality . It became extremely popular in broadcast stations and project studios due to its compact size and reliable operation . The machine features extensive use of plug-in cards, making servicing relatively straightforward compared to earlier point-to-point wired designs .

Current Market Value (2024)

A807 values reflect its professional heritage, versatility, and continued demand in studios:

Note: The A807 is more affordable than the larger A820 but shares much of the same technology. Machines with complete documentation, original manuals, and professional restoration command premium prices. The 1/2" two-track version is particularly sought after for mastering applications .

Common Failure Modes

#1 Frako Electrolytic Capacitor Failure (The #1 Killer)

Symptom: Missing power rails, blown fuses, dead channels, intermittent operation, microprocessor glitches, display issues . One technician noted: "The biggest issue is the Frako caps - they WILL fail and cause all sorts of weird problems" .

Cause: The A807 uses numerous Frako electrolytic capacitors throughout the power supplies, audio cards, and transport control boards . These capacitors are infamous for drying out, leaking electrolyte, and shorting catastrophically after 30+ years .

Repair: Replace ALL Frako electrolytic capacitors on sight . This includes power supply boards, audio cards, and transport control boards . Use high-quality 105°C rated capacitors from reputable brands (Nichicon, Panasonic, Vishay) .

#2 RIFA "Exploding" Capacitor Failure

Symptom: Smoke, burning smell, loud cracking, blown fuses, tripped breakers. One user reported: "The RIFA caps on the mains input had exploded, leaving soot everywhere" .

Cause: Paper dielectric RIFA capacitors absorb moisture over decades and short catastrophically .

Repair: Replace ALL RIFA capacitors on sight before applying power. Found on mains input, power supply boards, and across motor run capacitors . Replace with X2 class safety capacitors .

#3 "DSC" Error or Transport Not Responding

Symptom: Machine powers on but displays "DSC" error, transport buttons don't work, or transport behaves erratically .

Cause: Failed capacitors on the DSC (Digital Servo Control) board . The DSC board uses many small electrolytics that dry out, causing servo control issues .

Repair: Replace all electrolytic capacitors on the DSC board (1.807.450) . Pay special attention to capacitors in the servo feedback circuits .

#4 Tension Sensor Board Issues

Symptom: Erratic tape tension, tape spillage, oscillation in fast wind, "Tension Error" messages .

Cause: The tension sensor board (1.807.416) uses opto-electronic sensors that can drift or fail . The associated capacitors also degrade .

Repair: Clean the opto-interrupters, check for proper alignment, replace capacitors on the tension sensor board .

#5 Power Supply Capacitor Failure (1.807.400 Series)

Symptom: Voltage fluctuations, intermittent operation, blown fuses, display flicker .

Cause: The A807 uses multiple power supply boards (often 1.807.400 series) with numerous Frako electrolytics that fail .

Repair: Replace all electrolytic capacitors on all power supply boards . Use low-ESR, 105°C rated capacitors for switching power supply sections .

#6 Audio Channel Capacitor Failure

Symptom: Distorted audio, low output, one channel dead, noise, hum .

Cause: The audio boards (record and playback) contain many small electrolytics that dry out . Coupling capacitors lose capacitance, causing low output and poor frequency response .

Repair: Replace all electrolytic capacitors on audio boards . For best results, use audio-grade capacitors (Nichicon FG, Elna Silmic II) in the signal path .

#7 Microprocessor Reset Issues

Symptom: Machine doesn't boot, freezes randomly, buttons unresponsive .

Cause: Failed capacitors in the microprocessor reset circuit . The reset circuit relies on a capacitor that can leak or lose capacitance, preventing proper startup .

Repair: Check reset circuit voltages, replace capacitors in the reset circuit even if they test good for capacitance - they may leak .

#8 Motor Run Capacitor Failure

Symptom: Capstan motor runs hot, won't start, speed instability, reel motors weak .

Cause: Motor run capacitors (typically 4µF and 8µF values) degrade over time . The A807 uses separate capacitors for capstan and reel motors .

Repair: Replace with modern polypropylene motor run capacitors . Verify correct values for your configuration (50Hz vs 60Hz) .

#9 Capstan Motor Bearing Wear

Symptom: Grinding noise, wow and flutter, speed instability .

Cause: The direct-drive capstan motor bearings can wear over decades of use .

Repair: Capstan motor rebuild by specialist (requires disassembly, bearing replacement, and reassembly) .

#10 Pinch Roller Solenoid Issues

Symptom: Pinch roller doesn't engage properly, tape slips, squealing .

Cause: The pinch roller solenoid may be weak, or its pivot points may be dry and sticky .

Repair: Clean and lubricate solenoid pivot points . Check solenoid voltage . Replace solenoid if weak .

#11 Display Dimming or Missing Segments

Symptom: Vacuum fluorescent display dim, missing digits, flickering .

Cause: Aging VFD, or failed capacitors in the display power supply .

Repair: Replace capacitors on display power supply board . If display itself is failing, replacement VFDs are available from specialist suppliers .

#12 Toggle Switch and Potentiometer Noise

Symptom: Crackling when adjusting controls, intermittent operation .

Cause: Oxidation on switch contacts and potentiometer tracks after 30+ years .

Repair: Clean with DeOxit or appropriate contact cleaner . For stubborn cases, replace switches/pots .

⚠️ CRITICAL: A807 Error Codes

The A807 microprocessor can display error codes that help diagnose problems :

Note: Error codes can be triggered by capacitor failures in the associated circuits. Always check power supply voltages and capacitor health when troubleshooting errors .

Critical Board Identification

Systematic Restoration Process

Pro Tip: One restorer notes: "The A807 is very sensitive to capacitor health. A single bad cap can cause the entire transport to behave erratically. Don't skip the DSC board - it's often the culprit for DSC errors."

Complete Capacitor Replacement Guide

Note: Values may vary based on specific configuration (50Hz vs 60Hz). Verify with your machine's documentation .

• Use high-quality capacitors: Nichicon, Panasonic, Vishay, WIMA
• For audio path, consider audio-grade capacitors (Nichicon FG, Elna Silmic II)
• Use 105°C rated capacitors for power supply and high-temperature areas
• Increase voltage ratings where physically possible for safety margin
• Confirm polarity during installation
• Clean boards thoroughly after removing old caps (Frako electrolyte is corrosive)

Microprocessor and Memory Issues

Backup Battery:

• The A807 uses a battery to maintain calibration data and setup parameters
• Original batteries may leak and corrode the board
• Replace with new lithium battery (CR2032 or similar with holder)
• After battery replacement, calibration data may be lost - machine may display "no CAL"
• Full recalibration required after battery replacement

EEPROM Failure:

• The A807 stores calibration data in EEPROM
• EEPROM can fail or become corrupted
• Symptoms: "PAr" error, incorrect operation, lost settings
• Replacement EEPROMs available from Studer specialists
• Must be programmed with correct data for your configuration

Reset Circuit:

• Capacitors in the reset circuit can leak, preventing proper microprocessor startup
• Symptoms: machine doesn't boot, freezes randomly
• Replace all electrolytics in reset circuit even if they test good for capacitance

Complete Troubleshooting Guide

Real Restoration Cases:

Calibration and Alignment

Required Tools:

• MRL test tape (appropriate for track configuration and EQ curve)
• Oscilloscope (for azimuth and bias adjustment)
• Audio signal generator
• AC millivoltmeter
• Distortion analyzer (optional)
• Tension gauge
• Non-magnetic screwdrivers
• Frequency counter (for speed calibration)

Alignment Sequence :

1. Mechanical alignment: Tape path, head height, zenith
2. Playback alignment: Level and EQ using test tape
3. Record alignment: Bias adjustment, record level, EQ
4. Azimuth adjustment: Using test tape for playback, then record/playback loop
5. Speed calibration: Adjust capstan speed using frequency counter
6. Tension adjustment: Set tape tension per service manual

Setup Mode:

The A807 has a setup mode accessible via front panel buttons that allows adjustment of various parameters including:

• Speed settings
• Tape tension values
• Display brightness
• Remote control configuration
• Bias and EQ settings

Mechanical Maintenance Guide

Capstan Motor Service:

• Listen for bearing noise (grinding, rumbling)
• If noisy, motor may need professional rebuild
• Some motors have lubrication ports - use appropriate oil (PDP65) sparingly

Pinch Roller Solenoid:

• Check for smooth operation, no binding
• Clean pivot points and lubricate lightly
• Check solenoid voltage when engaged

Tape Path Cleaning:

• Clean heads, guides, and rollers with isopropyl alcohol
• Check for oxide buildup on all tape contact points
• Clean capstan shaft thoroughly

Tension Sensor Adjustment:

• Clean opto-interrupters with compressed air or alcohol
• Check alignment of light barriers
• Adjust per service manual if tension errors persist

Brake Adjustment:

• Check brake pads for wear
• Adjust brake tension to stop reels without excessive slack

Head Inspection:

• Visually inspect for wear groove
• If groove is visible (>0.5mm), relapping may be needed
• Studer heads typically last longer than most, but eventually wear
• JRF Magnetic Sciences offers relapping services

Restoration Kits & Resources

Specialist Suppliers:

Service Documentation:

• Studer FTP Archive: ftp://ftp.studer.ch/Public/Products/A807/ - Service manuals, schematics, bulletins
• HiFi Engine: User and service manuals
• Manualslib.com: A807 documentation

Online Communities:

• Tapeheads.net: Active Studer A807 discussions, many restoration threads
• GroupDIY: Technical discussions on Studer restoration
• Studer List (recordist.com): Email list for Studer enthusiasts
• Prodigy-Pro: Professional audio forum with A807 discussions

Technical Specifications

Common Mistakes to Avoid