Questions

What do you do to when you refurbish my unit ?

Here is an example of a repair and restore Pioneer RT-707

Restoring a Pioneer RT-707 reel-to-reel tape recorder to full working condition involves mechanical, electrical, and cosmetic steps. The RT-707 is a well-regarded machine known for its robust build, auto-reverse feature, and direct-drive capstan motor, but like any vintage audio equipment, it requires careful attention to bring it back to factory spec. Below is a detailed guide based on common practices for restoring reel-to-reel decks, tailored to the RT-707’s design and known issues. This assumes you have basic electronics skills, tools (e.g., multimeter, oscilloscope, soldering iron), and access to replacement parts.

Initial Assessment

• Power On Safely: Use a variac to slowly raise the voltage (start at 50V, gradually increase to 120V or your local voltage) to avoid damaging old capacitors. Check for signs of life, such as lights, motor movement, etc.
• Visual Inspection: Look for obvious damage—burnt components, cracked belts, sticky residue from degraded rubber, or corrosion on connectors.
• Listen for Problems: Use headphones to check for hum, hiss, or channel imbalance during playback.
• Test Basic Functions: Try playback, fast forward, rewind, and record (with a test tape). Note issues like speed variation, no sound, or mechanical binding.

Mechanical Restoration

The RT-707’s transport relies on a direct-drive capstan motor and two reel motors, with pinch rollers and brakes that often need attention after decades of use.

• Clean and Lubricate:
• Pinch Rollers: Remove the pinch rollers (one screw each) and clean with isopropyl alcohol (90% or higher) to remove tape oxide buildup. If they’re hardened, shiny, or cracked, replace them (available from specialty audio suppliers like Vintage Electronics or eBay). Lubricate the pivot shaft with light machine oil (e.g., sewing machine oil) if it’s sticky.
• Capstan Shaft: Clean the capstan with alcohol and a lint-free cloth. Do not lubricate—it’s a direct-drive system and should run dry
• Reel Motors: Remove dust and debris with compressed air. Lubricate bearings sparingly with synthetic oil if they’re noisy or sluggish (check the manual for access points).
• Brakes: Inspect brake pads for wear. Clean with alcohol if sticky; replace if worn out (custom pads may need to be sourced or fabricated).
• Check Belts: The RT-707 has no main drive belt (direct-drive capstan), but the counter uses a small belt. If it’s stretched, cracked, or gooey, replace it (PRB or Marrs Communications sells compatible belts).
• Demagnetize: Use a handheld demagnetizer (e.g., Akai or RadioShack model) on the heads and metal tape path parts to remove residual magnetism. Keep it away from tapes and electronics during use.
• Tape Path: Clean the heads, guides, and tension arms with alcohol and cotton swabs. Use a rubber cleaner (e.g., Craig CaiKleen) for stubborn residue
• Adjust Tape Tension: Test with a 7-inch reel. If the tape slips or skews, adjust the reel motor torque or brake tension (refer to the service manual—available on HiFi Engine—for exact procedures).
• Demagnetize: Use a handheld demagnetizer (e.g., Akai or RadioShack model) on the heads and metal tape path parts to remove residual magnetism. Keep it away from tapes and electronics during use.

Electrical Restoration

The RT-707’s electronics include power supply, audio circuits, and control logic, all of which can degrade over time.

• Replace Capacitors:
• Power Supply: Recap the power board (RNP-370) with new electrolytic capacitors. Common values include 1000µF 35V, 470µF 25V, etc. (check schematic). Use high-quality brands like Nichicon or Panasonic, matching voltage and capacitance.
• Audio Boards: Replace electrolytes on the record/playback amps (e.g., 10µF 25V, 47µF 16V). Tantalum caps (if present) may need swapping for modern equivalents if they’re shorted.
• Transport Control: Recap the logic board if speed or switching is erratic (small values like 1µF 50V are common). Test old caps with a meter for leakage or capacitance loss before replacing, but at 40+ years old, proactive replacement is safer.

Clean Switches and Pots

• Use DeoxIT D5 on all switches (tape monitor, rec on/off, speed select) and potentiometers (input/output levels, bias/EQ). Spray, work them through their range, and repeat. Avoid over-spraying onto nearby components.
• If scratchy audio persists, disassemble and clean contacts with alcohol, then apply DeoxIT FaderLube.

Check Transistors:

• Test key transistors (e.g., 2SC945, 2SA733) in the audio and motor control circuits with a multimeter. Replace noisy or failed ones with modern equivalents (e.g., KSC1845, KSA733). The direct-drive servo circuit is critical—erratic speed often points here.

Inspect Solder Joints

• Reflow cracked or cold joints, especially on the power supply and head preamp boards

Replace bulbs

• Swap burnt-out VU meter or transport lamps with LEDs or exact incandescent replacements (8V 200mA, available online). LEDs need a resistor (e.g., 470Ω) in series.

Calibration

• Speed Adjustment: Play a 3kHz test tone and tweak the capstan motor pot (VR1 on the servo board) until the frequency is stable at 3000Hz ±10Hz. Wow/flutter should be below 0.05% WRMS (spec).
• Azimuth: Play a 10kHz test tone and adjust the playback head screw until both channels peak equally on the scope.
• Tilt: Height and Use a mirror tape or visual check to ensure the tape runs centered over the heads. Adjust as needed.
• Bias and EQ:Record a 1kHz tone at 0VU, adjust bias pots (VR3/VR4) for max output, then back off slightly past the peak (per manual). Record 10k

Common issues

When you hit "play" on a Unit , the expected behavior is that the pinch roller engages the capstan, the take-up reel starts turning, and the tape begins to move across the heads for playback. If this isn’t happening, there could be several issues:

1. Pinch Roller Not Engaging: If the pinch roller doesn’t move toward the capstan or only engages briefly before disengaging, it could be due to a gummed-up solenoid or hardened grease in the pinch roller mechanism. Manually moving the roller up and down repeatedly might free it up by softening old grease, or it may need cleaning and lubrication

2.Capstan Not Spinning:: If the capstan shaft (the metal rod next to the heads) isn’t turning, the issue might be a stretched, slipped, or broken capstan belt. This is a common failure in older units, especially after long storage. A loose or missing belt would prevent the tape from moving even if the reels spin.

If the take-up reel doesn’t rotate in play mode, it could indicate a problem with the reel motor, a blown fuse, or a tension arm microswitch failure. The right tension arm must be raised for the deck to function; if its microswitch is faulty, the play function might not activate fully.

3. Reels Not Turning: If the take-up reel doesn’t rotate in play mode, it could indicate a problem with the reel motor, a blown fuse, or a tension arm microswitch failure. The right tension arm must be raised for the deck to function; if its microswitch is faulty, the play function might not activate fully.

Clicking or Stopping: Some users report a clicking sound or the deck stopping shortly after pressing play. This could point to a brake relay issue, a solenoid problem, or even a tape tension issue causing the deck to shut off as a safety feature.

5. No Response at All: If nothing happens when you press play (no movement, no sound), it might be an electrical issue—check the fuses, power supply, or control circuitry. The deck’s transport relies on relays and switches that can fail over time.

What to Check:

• Tape Threading: Ensure the tape is threaded correctly—shiny side against the heads, following the path over the left tension arm, under the guides, and below the right tension arm.
• Capstan Belt: Open the back and inspect the belt. If it’s loose, sticky, or off the pulley, it needs replacing.
• Pinch Roller Condition: Check if it’s hard, gooey, or stuck. A sluggish roller can often be freed up manually or may need cleaning (use

• Clean and Lubricate:
• Capstan Shaft: Clean the capstan with alcohol and a lint-free cloth. Do not lubricate—it’s a direct-drive system and should run dry.
• Pinch Rollers: Remove the pinch rollers (one screw each) and clean with isopropyl alcohol (90% or higher) to remove tape oxide buildup. If they’re hardened, shiny, or cracked, replace them (available from specialty audio suppliers like Vintage Electronics or eBay). Lubricate the pivot shaft with light machine oil (e.g., sewing machine oil) if it’s sticky.
• Reel Motors: Remove dust and debris with compressed air. Lubricate bearings sparingly with synthetic oil if they’re noisy or sluggish (check the manual for access points).
• Brakes: Inspect brake pads for wear. Clean with alcohol if sticky; replace if worn out (custom pads may need to be sourced or fabricated).
• Check Belts: The RT-707 has no main drive belt (direct-drive capstan), but the counter uses a small belt. If it’s stretched, cracked, or gooey, replace it (PRB or Marrs Communications sells compatible belts).
• Tape Path: Clean the heads, guides, and tension arms with alcohol and cotton swabs. Use a rubber cleaner (e.g., Craig CaiKleen) for stubborn residue.
• Demagnetize: Use a handheld demagnetizer (e.g., Akai or RadioShack model) on the heads and metal tape path parts to remove residual magnetism. Keep it away from tapes and electronics during use.
• Adjust Tape Tension: Test with a 7-inch reel. If the tape slips or skews, adjust the reel motor torque or brake tension (refer to the service manual—available on HiFi Engine—for exact procedures).

Cleaning Supplies: For cleaning reel heads, you'll need cotton swabs and a specialized cleaning solution. These can often be found at electronic or audio equipment stores, or ordered online. Regular cleaning can resolve many common issues with reel-to-reel machines. Lubrication and Maintenance Tools: To maintain the mechanical parts like motors, capstan shafts, and pinch roller bearings, you'll need light sewing machine oil or similar lubricants. The service manual might specify the exact type of lubricant needed for your model. For example, the TEAC A-3340S requires lubrication through oiling tubes on each end of the motor. Magnetic Head Care: For heads that might need reconditioning, you could look into companies like Fluxmagnetics for head fabrication or relapping services. These services are crucial for maintaining or enhancing the audio quality of your recordings. Replacement Parts: Depending on the specific issue, you might need to replace components like belts, pulleys, or even electronic parts. Websites like eBay offer a range of parts, from vintage to modern, but for specialized reel-to-reel parts, you might have to look at niche forums or contact specialized repair services. Service Manuals: Having access to the service manual for your specific model is invaluable. These manuals guide you through disassembly, repair, and reassembly processes for reel-to-reel machines. Service manuals can often be found through online archives, forums, or directly from manufacturers if they still exist. Test Equipment: Professional repair might require test equipment like tape deck analyzers for calibration and ensuring the machine's performance post-repair. Companies like Reel-to-Reel Tech mention using tools like the Nakamichi T-100 for such purposes. Specialty Tools: For more intricate repairs, you might need specialty tools like Allen and hex keys, which are specifically sized to not strip screws in audio equipment. These can be sourced from hardware stores or online retailers specializing in audio repair tools. Software and Digital Tools: While not a physical tool, understanding software for audio restoration or digital transfer can be crucial if you're dealing with tape issues like sticky shed syndrome or if you're looking to digitize your reels. Services like Audio Conservation provide insights into these processes.

Step-by-Step Restoration Process

1.Initial Assessment

• Inspect the Player: Check for visible damage—cracked belts, worn rollers, rust, or broken parts. Plug it in (briefly) to see if it powers on, and listen for unusual noises (grinding, squeaking).
• Gather Info: If possible, find the service manual for your specific reel-to-reel model (e.g., Teac, Akai, Revox Pineer). These often include schematics and calibration instructions.

2.Cleaning

• Unplug the Machine: Safety first—never work on it while powered.
• Exterior: Wipe the case with a damp cloth (no harsh chemicals). Avoid getting water inside.
• Tape Path: Use isopropyl alcohol and cotton swabs to clean the tape heads, capstan, pinch roller, and guides. Remove dust, oxide buildup, or sticky residue from old tape.
• Pinch Roller: If it’s hard or shiny (glazed), clean it with rubber cleaner. Replace it if it’s cracked or doesn’t grip properly.
• Controls: Use contact cleaner on potentiometers (volume/tone knobs) and switches if they’re scratchy or unresponsive.

3. Mechanical Restoration

• Belts: Check the rubber belts driving the motors and reels. If they’re stretched, cracked, or gooey, replace them. Measure the old belts (circumference and width) to order exact replacements.
• Idler Wheels: Inspect the rubber idler wheel (if present). Clean with rubber conditioner or replace if it’s worn or hardened
• Lubrication: Apply a small amount of appropriate oil or grease to bearings, motor shafts, and moving parts (refer to the manual—over-lubrication can attract dust)
• Brakes: Test the brake mechanism (if applicable). Clean and adjust tension so reels stop smoothly without jerking.
• Capstan and Motor: Ensure the capstan spins freely. Clean the shaft with alcohol if it’s gummed up. Check motor noise and lubricate if needed

4.Electrical Restoration

• Grounding: Ensure all grounding points are secure to avoid hum or noise
• Transistors/Tubes: If it’s a tube-based machine, test the tubes. For solid-state models, check transistors for shorts or failures.
• Switches and Pots: Spray contact cleaner into noisy or sticky controls, working them back and forth to distribute it.
• Power Supply: Check the power cord and plug for damage. Use a multimeter to test voltage at key points (refer to the manual).
• Capacitors: Old electrolytic capacitors (especially in machines from the ‘60s or ‘70s) may be dried out or leaking. Replace them if they look bulging or test bad with a multimeter.

5.Tape Head Maintenance

• Cleaning: Use isopropyl alcohol and a swab to clean the heads thoroughly.
• Demagnetizing: Run a demagnetizer over the heads and metal parts of the tape path to remove residual magnetism (do this with the machine off).
• Alignment: Use a test tape (with calibration tones) to check head alignment. Adjust azimuth (head angle) with a small screwdriver until the playback sound is crisp and clear, maximizing high frequencies.

6.Calibration

• Speed Check: Use a test tape or a strobe disc to verify tape speed (e.g., 7.5 ips or 3.75 ips). Adjust the motor speed control (if adjustable) with a trim pot.
• Bias and EQ: Adjust recording bias and equalization settings per the manual, using a test tape and an oscilloscope or audio analyzer if possible.
• Playback Levels: Set playback gain so the VU meters read accurately with a standard test signal.

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