Pioneer RT-707 Restoration Guide
Capacitor Replacement + Mechanical Issues & Solutions
1. Power Supply Board (RWR-053 / AWR-054)
Most Critical Board - Start Here
| Capacitor |
Value |
Location |
Symptoms When Failing |
| C9, C10 |
1000µF, 25V |
Near transformer input |
Hum, low power, unstable voltage |
| C7, C8 |
100µF, 25V |
Near voltage regulators |
Noise in audio circuits |
| C13, C14 |
47µF, 25V |
Capstan motor control circuit |
ERRATIC MOTOR SPEED or RUNAWAY |
2. Mic / Line Amp Board (RWB-068 / AWB-068)
Affects Recording Quality
| Capacitor |
Value |
Location |
Symptoms When Failing |
| C1, C2 |
1µF, 50V |
Input jacks (left & right channels) |
Low/distorted record signal |
| C9, C10 |
100µF, 16V |
Op-amp power supply |
General audio issues |
3. Playback Amp Board (RWB-069 / AWB-069)
Affects Playback Quality
| Capacitor |
Value |
Location |
Symptoms When Failing |
| C1, C2 |
1µF, 50V |
Playback head input circuit |
WEAK or DEAD PLAYBACK |
4. Oscillator / Bias Board (RWB-070 / AWB-070)
Critical for Recording Function
| Capacitor |
Value |
Location |
Symptoms When Failing |
| C7, C8 |
4.7µF, 25V |
Bias output circuit |
Poor high-frequency response or NO RECORDING |
5. Relay / Control Board (RWB-072)
Affects Mechanical Operation
| Capacitor |
Value |
Location |
Symptoms When Failing |
| C1 |
100µF, 16V |
Near control relay |
LOUD THUMP in speakers when stopping |
🔧 Common Mechanical Issues & Solutions
Pinch Roller Assembly
| Problem |
Symptoms |
Solution |
| Dry/Stiff Bearing |
Squealing noise, poor tape transport |
Clean old grease, lubricate with synthetic grease |
| Hardened Rubber |
Poor tape grip, wow/flutter |
Replace pinch roller or rejuvenate with rubber restorer |
Brake System
| Problem |
Symptoms |
Solution |
| Sticking Brakes |
Tape spillage, uneven winding |
Clean brake mechanism, adjust tension |
| Worn Felt |
Slipping, poor braking |
Replace brake felt pads |
Transport Mechanism
| Problem |
Symptoms |
Solution |
| Old Hardened Grease |
Stiff operation, slow response |
Complete disassembly, clean old grease, re-lubricate |
| Worn Idler Wheels |
Slipping, poor torque |
Replace or resurface idler wheels |
Tape Counter & Belts
| Problem |
Symptoms |
Solution |
| Broken Counter Belt |
Tape counter not moving |
Replace with new rubber belt |
| Sticky Counter |
Counter jumps or sticks |
Clean and lubricate counter mechanism |
Auto-Shutoff Mechanism
| Problem |
Symptoms |
Solution |
| Failed Sensor |
No auto-stop at tape end |
Clean optical sensor or replace lamp |
| Mechanical Jam |
Shutoff doesn't engage |
Clean and free up mechanical linkage |
⚠️ Important Safety Notes
- DISCHARGE CAPACITORS before working - especially the large C9, C10 on power supply
- GET SERVICE MANUAL - Essential for schematics and board layouts
- CHECK ACTUAL VALUES - Verify capacitor values on your specific unit before replacement
- REPLACE TRANSISTORS Q301-Q304 - Known failure points causing channel dropouts
🛠️ Mechanical Service Tips
- Use proper lubricants - Synthetic grease for slow-moving parts, light oil for bearings
- Clean before lubricating - Remove all old grease completely
- Take photos during disassembly - Helps with reassembly
- Don't force mechanisms - If something sticks, find the cause
