Marantz 1060 Stereo Integrated Amplifier Restoration

Unit: Stereo Integrated Amplifier

Manufacturer: Marantz

Model: 1060

SN: 13050

Today, I'm showcasing one of the most well-known, respected, and popular integrated amplifiers of the 70's. This amplifier is one of the most valuable among collectors, and its price only gets higher over time. As many of you might guess, this is a Marantz Model 1060.

Marantz 1060 was manufactured from 1971 to 1978. It produces 30 watts per channel into 8 ohms with no more than 0.5% total harmonic distortion. The optional walnut veneer cabinet for this model is WC-10.

Power Supply Board (P800)

The power supply unit provides +35V DC (pin J806) to the phono amplifier and +27V DC (pin J807) to the tone & pre-amplifier board. 

 

Four electrolytic capacitors (C803, C804, C805, and C806) installed on this board were replaced with low-impedance, high-reliability Nichicon UPW/UPM e-caps. The dried glue under each capacitor was carefully removed. The original e-caps were tested using an Atlas ESR70 capacitance meter. The capacitance of two out of the four capacitors was found to be outside the factory tolerance of ±20%.

Test results on original capacitors removed from the power supply board:

C803: rated capacitance – 470uF, measured – 549uF, ESR – 0.01Ω, deviation: +17%

C804: rated capacitance – 100uF, measured – 161uF, ESR – 0.06Ω, deviation: +61%

C805: rated capacitance – 330uF, measured – 353uF, ESR – 0.02Ω, deviation: +7%

C806: rated capacitance – 100uF, measured – 154uF, ESR – 0.03Ω, deviation: +54%

The original semiconductor devices on this board were also replaced to improve the reliability of the power supply. The regulating transistor 2SC1318, located at position H801, was replaced with a new Fairchild KSC2383YTA. The two SIB-01-02 diodes at positions H802 and H803 were upgraded to fast recovery rectifiers (UF4005).

Power supply board - before and after

Tone & Pre-Amplifier Board (P400)

The tone and pre-amplifier board contains eight low-leakage capacitors (C403, C404, C407, C408, C410, C411, C412, C413), two bipolar electrolytic capacitors (C414, C415), and three aluminum electrolytic capacitors (C405, C406, C409). The original low-leakage capacitors (except for C407 and C408) and both bipolar capacitors were replaced with high-quality WIMA polyester film capacitors. Capacitors C407 and C408 were replaced with low-leakage Nichicon UKL caps. The remaining aluminum electrolytic capacitors were replaced with low-impedance Nichicon UPW/UPM caps.

Test results on original capacitors removed from the tone & pre-amplifier board:

C403: rated capacitance – 1uF, measured – 1uF, ESR – 4.4Ω, deviation: 0%

C404: rated capacitance – 1uF, measured – 1uF, ESR – 4.2Ω, deviation: 0%

C405: rated capacitance – 10uF, measured – 10uF, ESR – 1.56Ω, deviation: 0%

C406: rated capacitance – 10uF, measured – 10uF, ESR – 1.63Ω, deviation: 0%

C407: rated capacitance – 3.3uF, measured – 3.5uF, ESR – 1.87, deviation: +6%

C408: rated capacitance – 3.3uF, measured – 3.4uF, ESR – 2.1Ω, deviation: +3%

C409: rated capacitance – 100uF, measured – 104uF, ESR – 0.09Ω, deviation: +4%

C410: rated capacitance – 3.3uF, measured – 3.5uF, ESR – 2.1Ω, deviation: +6%

C411: rated capacitance – 3.3uF, measured – 3.4uF, ESR – 2.6Ω, deviation: +3%

C412: rated capacitance – 0.47uF, measured – 0.48uF, ESR – N/A, deviation: +2%

C413: rated capacitance – 0.47uF, measured – 0.48uF, ESR – N/A, deviation: +2%

C414: rated capacitance – 1uF, measured – 1uF, ESR – 2.6Ω, deviation: 0%

C415: rated capacitance – 1uF, measured – 1uF, ESR – 2.8Ω, deviation: 0%

All original Toshiba 2SC1000 transistors installed on this board were replaced with modern low-noise Fairchild KSC1845s. The replacement transistors share the same pinout as the originals, ensuring a straightforward drop-in replacement.

According to the service manual, the PNP transistors in this circuit should be 2SA493. However, this board was populated with 2SA702 transistors instead. Although the failure modes of the 2SA702 are not well documented, they are known to be less reliable and have also been replaced. New Fairchild KSA992 transistors were installed in place of the 2SA702s to improve long-term reliability.

Tone & pre-amp board - before and after

Phono Amplifier Board (P900)

The phono amplifier board contains four low-leakage capacitors (C901, C902, C905, C906) and three aluminum electrolytic capacitors (C909, C910, C919). The original low-leakage capacitors at positions C901 and C902 were replaced with high-quality WIMA polyester film capacitors. The remaining two low-leakage capacitors (C905 and C906) were replaced with modern low-leakage Nichicon UKL types. The aluminum electrolytic capacitors were upgraded to low-impedance Nichicon UPW/UPM series.

Test results on original capacitors removed from the phono amplifier board:

C901: rated capacitance – 1uF, measured – 0.9uF, ESR – 4.2Ω, deviation: -10%

C902: rated capacitance – 1uF, measured – 1uF, ESR – 3.8Ω, deviation: 0%

C905: rated capacitance – 22uF, measured – 23uF, ESR – 0.31Ω, deviation: +5%

C906: rated capacitance – 22uF, measured – 23uF, ESR – 0.68Ω, deviation: +5%

C909: rated capacitance – 47uF, measured – 66uF, ESR – 0.32Ω, deviation: +40%

C910: rated capacitance – 47uF, measured – 57uF, ESR – 0.35Ω, deviation: +21%

C919: rated capacitance – 100uF, measured – 138uF, ESR – 0.12Ω, deviation: +38%

This board also contains two types of notoriously unreliable transistors: 2SC1000 and 2SC458. Both are known to become noisy over time and are common sources of audio issues. I replaced all of them with modern low-noise Fairchild KSC1845 transistors. Transistors H905 and H906 were gain-matched within 1% for optimal performance.

Pay close attention to pinout orientation when installing replacements. The original 2SC1000 shares the same ECB pinout as the KSC1845. However, the 2SC458 has a BCE pinout.

Phono amplifier board  - before and after

Power Amplifier Board (P700)

The power amplifier board in this unit had been previously serviced, but unfortunately, the work was done poorly. Low-quality electrolytic capacitors were installed in several positions, and the overall soldering quality is very unreliable. In one case, a resistor lead was bent through the PCB hole but left unsoldered, posing a risk of intermittent connection or failure. Due to these issues, all previous work needed to be redone to ensure proper function and long-term reliability.

Bad soldering, one lead was bent but not soldered to the PCB

The power amplifier board contains four low-leakage electrolytic capacitors (C701, C702, C711, C712) installed in the signal path, along with eight aluminum electrolytic capacitors (C703, C704, C707, C708, C709, C710, C717, C718). The original low-leakage capacitors at positions C701 and C702 were replaced with WIMA polyester film capacitors. The remaining low-leakage capacitors (C711 and C712) were replaced with modern low-leakage Nichicon UKL caps. All remaining aluminum electrolytic capacitors were upgraded to low-impedance Nichicon UPW/UPM series.

I tested all the electrolytic capacitors removed from this board using an Atlas ESR70 capacitance meter, and the results are as follows: the measured capacitance of C709 was only 13µF, representing a 72% deviation from the rated value. Additionally, capacitor C718 failed the test entirely, exhibiting either an open circuit or very low capacitance.

Test results on original capacitors removed from the power amplifier board:

C701: rated capacitance – 1uF, measured – 1uF, ESR – 4.1Ω, deviation: 0%

C702: rated capacitance – 1uF, measured – 0.9uF, ESR – 4.3Ω, deviation: -10%

C703: rated capacitance – 47uF, measured – 45uF, ESR – 0.52Ω, deviation: -4%

C704: rated capacitance – 47uF, measured – 55uF, ESR – 0.1Ω, deviation: +17%

C707: rated capacitance – 47uF, measured – 48uF, ESR – 0.32Ω, deviation: +2%

C708: rated capacitance – 47uF, measured – 57uF, ESR – 0.28Ω, deviation: +21%

C709: rated capacitance – 47uF, measured – 13uF, ESR – 0.85Ω, deviation: -72%

C710: rated capacitance – 47uF, measured – 46uF, ESR – 0.26Ω, deviation: -2%

C711: rated capacitance – 10uF, measured – 11uF, ESR – 1.43Ω, deviation: +10%

C712: rated capacitance – 10uF, measured – 11uF, ESR – 1.16Ω, deviation: +10%

C717: rated capacitance – 22uF, measured – 22uF, ESR – 2.5Ω, deviation: 0%

C718: rated capacitance – 22uF, measured – open circuit/low capacitance

Both original pre-driver transistors (H701 & H702) were upgraded to the new Fairchild KSC945CYTA.

The original trimming resistors R723/R724 (100 kΩ, clipping level) and R729/R730 (470 Ω, Bias) were replaced with new Bourns potentiometers.

Power amplifier board - before and after

Power Transistors

Two power transistors in the left channel of this unit had been previously replaced with Sylvania ECG280 transistors, while the two transistors in the right channel are original Marantz 2SC897D. I tested all power transistors using an Atlas DCA55 semiconductor analyzer, and all of them are still functioning properly. However, I am unfamiliar with the performance and quality of Sylvania power transistors, which raised concerns regarding their long-term reliability. As a precaution, I decided to replace all four power transistors with new ON Semiconductor MJ21194G transistors.

These new transistors are specifically designed for high-power audio output and offer excellent gain linearity. According to the datasheet, the total harmonic distortion (THD) for two matched pairs of MJ21194G transistors can be as low as 0.08%, making them an ideal replacement for the original 2SC897D. To ensure optimal thermal management, new mica pads and fresh thermal compound were applied between each power transistor and the heat sink. Additionally, fresh thermal compound was also applied to the thermal tracking diodes H005 and H006 to maintain proper temperature regulation.

Old power transistors (Sylvania ECG280 and Marantz 2SC897D)

New power transistors are installed (ON Semiconductor MJ21194G)

Missing Pre-OUT/Main IN terminal

For some unknown reason, the Pre-OUT/Main IN terminal, along with both jumper plugs, was missing from this unit. It appears that someone previously serviced the unit, removed the terminal from the rear panel, cut out the wires, and bypassed the Pre-OUT/Main IN terminal directly to the power amplifier board. This was not only an ineffective solution but also a disrespectful modification to such a fine amplifier.

To restore the unit to its original design, I installed a new terminal from my stock of spare parts and rewired all connections according to the schematic. Additionally, two resistors (R007 and R008, 220 kΩ, 1/4 W) were soldered between the input and ground as specified in the schematic diagram.

Missing Pre-OUT/Main IN terminal and jumper plugs

New Pre-OUT/Main IN terminal and jumper plugs are installed

Power Amplifier Adjustment

The Bias is measured across the emitter resistors R747 (jacks 713 & 715) and R748 (jacks 714 & 716). It was adjusted to ~7.5mV on each channel according to the service manual with trimming resistors R729 and R730.

The other two trimming resistors (R723 & R724) are used to adjust an equal and symmetrical clipping of the 1 kHz sine-wave signal.

Bias on the left and right channels after restoration

Output Power Test

The final output power test was performed at the end of my restoration. The amplifier was loaded with a low inductance 8Ω/100W dummy resistor for each channel. The oscilloscope was connected across the speaker terminals and a sine-wave signal of 1kHz was applied to the AUX jacks. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 16.54 VRMS (left channel) and 16.48 VRMS (right channel). It corresponds to the output power of 34.2W on the left channel and 33.9W on the right channel.

Output power test

As usual, all the knobs and the face plate were gently cleaned in warm water with dish soap. All controls have been cleaned with DeoxIT 5% contact cleaner and lubricated with DeoxIT FaderLube 5% spray.

The final result can be seen in the photos below. The amplifier looks brand new again and sounds awesome. Please watch a short demo video at the end of this post. Thank you for reading.

Marantz 1060 - before and after restoration, inside view

Marantz 1060 - after restoration

Demo video after repair & restoration

Sansui 2000X Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Sansui

Model: 2000X

SN: 812030260

Today I'm showcasing a Sansui 2000X receiver that came in for restoration. It was manufactured from 1971 to 1973 and produces 39 watts per channel into 8 ohms with no more than 0.8% total harmonic distortion. The frequency response is pretty impressive from 20Hz to 40kHz. The damping factor is 24.

According to the Sansui database, this particular unit was manufactured in March 1972.

Ripple Filter Block (F-1195-1)

This board has four aluminum electrolytic capacitors: C005, C006, C007, and C015. All of them were replaced with low impedance Nichicon UPW caps. The voltage rating was increased one step up on all capacitors.

Test results on original capacitors removed from the ripple filter block:

C005: rated capacitance – 220uF, measured – 248uF, ESR – 0.09Ω, deviation: +13%

C006: rated capacitance – 330uF, measured – 393uF, ESR – 0.08Ω, deviation: +19%

C007: rated capacitance – 330uF, measured – 376uF, ESR – 0.11Ω, deviation: +14%

C015: rated capacitance – 220uF, measured – 243uF, ESR – 0.08Ω, deviation: +11%

Ripple filter block - before and after

Rectifier Block (F-1197)

This board has only two aluminum electrolytic capacitors: C001 and C002. Both of them were replaced with low impedance UPW/UPM caps.

Test results on original capacitors removed from the rectifier block:

C001: rated capacitance – 220uF, measured – 218uF, ESR – 0.02Ω, deviation: -1%

C002: rated capacitance – 4.7uF, measured – 5.5uF, ESR – 1.11Ω, deviation: +17%

Rectifier block - before and after

Driver Amplifier Board (F-1180)

The driver amplifier board has twelve aluminum electrolytic capacitors (C802 thru C807, C812 thru C817). Two of them (C804 & C814) are installed in the signal path. I replaced them with high-quality film polyester WIMA caps to improve the signal-to-noise ratio. The remaining aluminum e-caps were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the driver amplifier board:

C802: rated capacitance – 100uF, measured – 120uF, ESR – 0.26Ω, deviation: +20%

C803: rated capacitance – 220uF, measured – 255uF, ESR – 0.25Ω, deviation: +16%

C804: rated capacitance – 1uF, measured – 1.1uF, ESR – 2.4Ω, deviation: +10%

C805: rated capacitance – 33uF, measured – 36uF, ESR – 0.32Ω, deviation: +9%

C806: rated capacitance – 100uF, measured – 114uF, ESR – 0.22Ω, deviation: +14%

C807: rated capacitance – 10uF, measured – 13uF, ESR – 0.81Ω, deviation: +30%

C812: rated capacitance – 100uF, measured – 129uF, ESR – 0.24Ω, deviation: +29%

C813: rated capacitance – 220uF, measured – 249uF, ESR – 0.24Ω, deviation: +13%

C814: rated capacitance – 1uF, measured – 1uF, ESR – 3.6Ω, deviation: 0%

C815: rated capacitance – 33uF, measured – 36uF, ESR – 0.33Ω, deviation: +9%

C816: rated capacitance – 100uF, measured – 117uF, ESR – 0.21Ω, deviation: +17%

C817: rated capacitance – 10uF, measured – 14uF, ESR – 0.92Ω, deviation: +40%

Two NPN transistors (TR801 & TR806) installed on this board are the notorious 2SC458LG. This transistor is prone to noise and I replaced both 2SC458LG with new Fairchild KSC1845. The new KSC1845 is a low-noise AF amplifier and is commonly used to replace noisy 2SC458LG transistor. Watch the pinout on replacement transistors if you need to service this board. The original transistor is BCE and the new is ECB.

Driver amplifier board (F-1180) - before and after

Tone Control Board (F-1222-1)

The tone control board has four low leakage e-caps (C707, C715, C721, C729) installed in the signal path, two axial aluminum e-caps (C712, C726), and seven radial aluminum e-caps (C703, C704, C706, CC714, C718, C720, C728). The original low leakage capacitors were replaced with film polyester WIMA caps. Two axial e-caps were replaced with new axial Vishay (138 AML series) capacitors. And, the remaining aluminum e-caps were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the tone control board:

C703: rated capacitance – 220uF, measured – 244uF, ESR – 0.15Ω, deviation: +11%

C704: rated capacitance – 33uF, measured – 37uF, ESR – 1.28Ω, deviation: +12%

C706: rated capacitance – 33uF, measured – 37uF, ESR – 0.76Ω, deviation: +12%

C707: rated capacitance – 1uF, measured – 1uF, ESR – 1.75Ω, deviation: 0%

C712: rated capacitance – 10uF, measured – 12uF, ESR – 1.21Ω, deviation: +20%

C714: rated capacitance – 47uF, measured – 61uF, ESR – 1.32Ω, deviation: +30%

C715: rated capacitance – 1uF, measured – 1uF, ESR – 2.6Ω, deviation: 0%

C718: rated capacitance – 33uF, measured – 36uF, ESR – 1.31Ω, deviation: +9%

C720: rated capacitance – 33uF, measured – 38uF, ESR – 0.77Ω, deviation: +15%

C721: rated capacitance – 1uF, measured – 1uF, ESR – 2.2Ω, deviation: 0%

C726: rated capacitance – 10uF, measured – 14uF, ESR – 1.06Ω, deviation: +40%

C728: rated capacitance – 47uF, measured – 68uF, ESR – 1.31Ω, deviation: +45%

C729: rated capacitance – 1uF, measured – 1uF, ESR – 2.6Ω, deviation: 0%

Six NPN transistors (TR701 thru TR706) installed on this board are the notorious 2SC458LG. I replaced them with a new Fairchild KSC1845. The new transistors were gain matched within 1%. Again, watch the pinout on replacement transistors if you need to service this board.

Tone control board - before and after

Equalizer Amplifier Board (F-1253)

The equalizer amplifier board has eleven aluminum electrolytic capacitors: C601, C603, C604, C606, C607, C611, C613, C614, C616, C617, and C626. Two of them (C601 & C611) are solid aluminum e-caps installed in the input signal path. I replaced them with film polyester WIMA caps. The other two capacitors (C607 & C617) installed in the output signal path are just ordinary aluminum e-caps. These were replaced with low leakage Nichicon UKL caps. The remaining aluminum capacitors were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the equalizer amplifier board:

C601: rated capacitance – 1.5uF, measured – 1.7uF, ESR – 4.4Ω, deviation: +13%

C603: rated capacitance – 33uF, measured – 36uF, ESR – 1.32Ω, deviation: +9%

C604: rated capacitance – 33uF, measured – 35uF, ESR – 1.35Ω, deviation: +6%

C606: rated capacitance – 47uF, measured – 59uF, ESR – 1.36Ω, deviation: +26%

C607: rated capacitance – 10uF, measured – 13uF, ESR – 1.86Ω, deviation: +30%

C611: rated capacitance – 1.5uF, measured – 1.4uF, ESR – 2.6Ω, deviation: -7%

C613: rated capacitance – 33uF, measured – 36uF, ESR – 1.33Ω, deviation: +9%

C614: rated capacitance – 33uF, measured – 36uF, ESR – 1.38Ω, deviation: +9%

C616: rated capacitance – 47uF, measured – 56uF, ESR – 1.57Ω, deviation: +19%

C617: rated capacitance – 10uF, measured – 11uF, ESR – 2.3Ω, deviation: +10%

C626: rated capacitance – 100uF, measured – 122uF, ESR – 0.51Ω, deviation: +22%

Four NPN transistors installed on this board are prone to noise 2SC871. I replaced them with a new Fairchild KSC1845. The new transistors were gain matched within 1%. Watch the pinout on replacement transistors if you need to service this board. The original transistor is BCE and the new is ECB.

Equalizer amplifier board - before and after

AM Meter Block (F-1220-1)

The AM meter block has two aluminum electrolytic capacitors: C335 and C345. The C345 is soldered on the foil side between the wiper terminal and the ground. The original capacitor C335 was replaced with a low impedance Nichicon UPW cap. The original capacitor C345 was replaced with a film polyester WIMA cap.

Test results on original capacitors removed from the AM meter block:

C335: rated capacitance – 4.7uF, measured – 7.3uF, ESR – 1.82Ω, deviation: +55%

C345: rated capacitance – 1uF, measured – 1.1uF, ESR – 2.8Ω, deviation: +10%

AM meter block - before servicing

AM meter block - after servicing

Accessories Block (F-1254-1)

The accessories block has only two aluminum electrolytic capacitors: C739 and C740. It is possible to replace these capacitors without disassembling the board from the chassis. I replaced them with film polyester WIMA caps. Sorry, I didn't take a picture of this board.

Test results on original capacitors removed from the accessories block:

C739: rated capacitance – 0.47uF, measured – 0.45uF, ESR – N/A, deviation: -4%

C740: rated capacitance – 0.47uF, measured – 0.51uF, ESR – N/A, deviation: +9%

Dial and Meter Lamps

The dial and meter lamps in this unit were replaced with new incandescent lamps (6V, 0.25A, screw base). The dial lamps can be accessed from the front panel when the scale is removed.

The stereo indicator and one function indicator lamp were blown out in this unit. I replaced them with new incandescent lamps as well. Access to these lamps is very limited and additional disassembling is required (at least the cover plate should be removed).

The cover plate removed to access the stereo indicator and function indicator lamps

New Stereo and AUX indicator lamps were installed

Idling Current and Symmetrical Clipping Adjustments

The idling current was adjusted to ~15mA on each channel according to the service manual. Two large trimming resistors (VR802 & VR804, 1kΩ each) are used for idling current adjustment.

Two small trimming resistors (VR801 & VR803, 200kΩ each) are used to adjust an equal clipping of the 1 kHz sine-wave signal.

Idling current on the left and right channels after restoration

Output Power Test

The final output power test was performed at the end of my restoration. The amplifier was loaded with a low inductance 8Ω/100W dummy resistor for each channel. The oscilloscope was connected across the speaker terminals and a sine-wave signal of 1kHz was applied to the AUX jacks. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 16.23 VRMS (left channel) and 16.13 VRMS (right channel). It corresponds to the output power of  32.9W on the left channel and 32.5W on the right channel.

Output power test

As usual, all the knobs and the front panel were gently cleaned in warm water with dish soap. All controls have been cleaned with DeoxIT 5% contact cleaner and lubricated with DeoxIT FaderLube 5% spray. The wood case was stained with Howard's Restor-A-Finish.

The final result can be seen in the photos below. The receiver looks brand new again and sounds fantastic! Classic Sansui receiver from the 70's! Please watch a short demo video at the end of this post. Thank you for reading.

Sansui 2000X - after restoration

Demo video after repair & restoration

Yamaha CR-1020 Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Yamaha

Model: CR-1020

SN: 01592

Another classic receiver from the 70's came on my bench for a full restoration. The Yamaha CR-1020 natural sound AM/FM receiver is the younger brother of the CR-2020 and CR-3020. It was manufactured from 1977 to 1980. It produces 70 watts per channel into 8 ohms with no more than 0.05% total harmonic distortion. This particular unit is from a private collection and came in excellent cosmetic condition. The wood case, front panel, and knobs are almost flawless.

Electrolytic Cap Board (NA 06903)

The electrolytic cap board has one low leakage e-cap (C813) and three aluminum electrolytic capacitors (C805, C806, C817). The original low leakage e-cap was replaced with modern low leakage Nichicon UKL cap. The remaining aluminum capacitors were replaced with low impedance Nichicon UPW/UPM caps. The original electronic capacitors removed from this board have been tested with an Atlas ESR70 capacitance meter and the results are shown below. Only one capacitor is out of factory tolerance spec. 

Test results on original capacitors removed from the electrolytic cap board:

C805: rated capacitance – 1000uF, measured – 824uF, ESR – 0.01Ω, deviation: -18%

C806: rated capacitance – 1000uF, measured – 753uF, ESR – 0.01Ω, deviation: -25%

C813: rated capacitance – 100uF, measured – 107uF, ESR – 0.08Ω, deviation: +7%

C817: rated capacitance – 220uF, measured – 189uF, ESR – 0.04Ω, deviation: -14%

Two large filter capacitors (C811/C812, 15000uF/63V) are also located on this board. I tested them in-circuit with a capacitance meter and they both are still in spec. So, I didn't change them. In general, the filter capacitors rarely fail in vintage gears, and I usually don't replace them unless their ESR is high.

In-circuit test on two filter capacitors - both are still in spec

C811: rated capacitance – 15000uF, measured – 13360uF, ESR – 0.01Ω, deviation: -11%

C812: rated capacitance – 15000uF, measured – 14200uF, ESR – 0.01Ω, deviation: -5%

The original fusible resistors FR801 & FR802 change the resistance value over time. It might result in intermittent power supply failure. I replaced them with Ohmite 22Ω 3 1/4 watt resistors according to the service bulletin for CR-2020.

The transformer was disassembled from the chassis to access the foil side of the PCB

Electrolytic cap board - before and after

Power Supply Board - 1 (NA 06899-1)

Two regulator transistors (TR712 and TR715) on the power supply board are running very hot under normal operating conditions. Eventually, these transistors often break down due to overheating. The original transistors installed in these positions are 2SD234. I replaced them with Fairchild MJE15030G and refresh the thermal paste between each transistor and heat sink. The collector power dissipation of the new Fairchild transistor is 50W whereas the original 2SD234 can dissipate only 25W. It will improve the reliability of the power supply circuit in this unit.

PCB under the heat sink with transistor TR712 - original transistor suffers from overheating

PCB under the heat sink with transistor TR712 - after cleaning

There are 31 aluminum electrolytic capacitors on the power supply board. All of them were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the power supply board:

C701: rated capacitance – 10uF, measured – 13uF, ESR – 2.01Ω, deviation: +30%

C702: rated capacitance – 10uF, measured – 13uF, ESR – 2.11Ω, deviation: +30%

C703: rated capacitance – 10uF, measured – 11uF, ESR – 2.2Ω, deviation: +10%

C704: rated capacitance – 10uF, measured – 11uF, ESR – 1.71Ω, deviation: +10%

C705: rated capacitance – 10uF, measured – 13uF, ESR – 1.85Ω, deviation: +30%

C706: rated capacitance – 10uF, measured – 13uF, ESR – 1.97Ω, deviation: +30%

C707: rated capacitance – 3.3uF, measured – 4.0uF, ESR – 2.4Ω, deviation: +21%

C708: rated capacitance – 3.3uF, measured – 3.8uF, ESR – 2.01Ω, deviation: +15%

C709: rated capacitance – 100uF, measured – 93uF, ESR – 0.61Ω, deviation: -7%

C710: rated capacitance – 100uF, measured – 95uF, ESR – 0.57Ω, deviation: -5%

C711: rated capacitance – 47uF, measured – 52uF, ESR – 1.04Ω, deviation: +11%

C712: rated capacitance – 47uF, measured – 53uF, ESR – 1.42Ω, deviation: +13%

C713: rated capacitance – 100uF, measured – 118uF, ESR – 0.71Ω, deviation: +18%

C714: rated capacitance – 100uF, measured – 108uF, ESR – 0.51Ω, deviation: +8%

C717: rated capacitance – 100uF, measured – 104uF, ESR – 3.4Ω, deviation: +4%

C718: rated capacitance – 10uF, measured – 11uF, ESR – 1.73Ω, deviation: +10%

C719: rated capacitance – 10uF, measured – 11uF, ESR – 1.52Ω, deviation: +10%

C720: rated capacitance – 10uF, measured – 11uF, ESR – 1.45Ω, deviation: +10%

C721: rated capacitance – 10uF, measured – 11uF, ESR – 1.21Ω, deviation: +10%

C722: rated capacitance – 10uF, measured – 11uF, ESR – 2.8Ω, deviation: +10%

C728: rated capacitance – 220uF, measured – 237uF, ESR – 0.24Ω, deviation: +8%

C729: rated capacitance – 1000uF, measured – 1196uF, ESR – 0.02Ω, deviation: +20%

C730: rated capacitance – 100uF, measured – 102uF, ESR – 0.42Ω, deviation: +2%

C732: rated capacitance – 220uF, measured – 251uF, ESR – 0.31Ω, deviation: +14%

C733: rated capacitance – 10uF, measured – 11uF, ESR – 3.4Ω, deviation: +10%

C734: rated capacitance – 47uF, measured – 50uF, ESR – 3.1Ω, deviation: +6%

C735: rated capacitance – 22uF, measured – 26uF, ESR – 0.98Ω, deviation: +18%

C736: rated capacitance – 22uF, measured – 26uF, ESR – 1.02Ω, deviation: +18%

C737: rated capacitance – 4.7uF, measured – 5.5uF, ESR – 2.5Ω, deviation: +17%

C738: rated capacitance – 47uF, measured – 28uF, ESR – 1.21Ω, deviation: -40%

C740: rated capacitance – 47uF, measured – 51uF, ESR – 0.78Ω, deviation: +9%

Power supply board - before and after

Pre Module Boards: A, B, C, D, and E

Five pre module boards (A, B, C, D, and E) are vertically mounted on the tone control board. All pre module boards can be easily removed from the tone control board for servicing if unsolder seven pins from each board.

The tone control board has only two low leakage e-caps C405 and C406 installed in the signal path. I replaced them with modern low leakage Nichicon UKL caps.

The pre module boards A and B are identical (NA 06898-1) and have three low leakage e-caps (C502, C509, C510) installed in the signal path and three aluminum e-caps (C504, C505, C508). All original low leakage e-caps were replaced with modern low leakage Nichicon UKL caps. The remaining aluminum capacitors were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the pre module boards A and B:

C502: rated capacitance – 10uF, measured – 8uF, ESR – 2.4Ω, deviation: -10%

C504: rated capacitance – 100uF, measured – 114uF, ESR – 0.33Ω, deviation: +14%

C505: rated capacitance – 220uF, measured – 279uF, ESR – 0.22Ω, deviation: +27%

C508: rated capacitance – 100uF, measured – 106uF, ESR – 0.28Ω, deviation: +6%

C509: rated capacitance – 22uF, measured – 20uF, ESR – 0.66Ω, deviation: -9%

C510: rated capacitance – 100uF, measured – 122uF, ESR – 0.18Ω, deviation: +22%

C502: rated capacitance – 10uF, measured – 9uF, ESR – 2.2Ω, deviation: -10%

C504: rated capacitance – 100uF, measured – 131uF, ESR – 0.46Ω, deviation: +31%

C505: rated capacitance – 220uF, measured – 213uF, ESR – 0.55Ω, deviation: -3%

C508: rated capacitance – 100uF, measured – 105uF, ESR – 0.22Ω, deviation: +5%

C509: rated capacitance – 22uF, measured – 22uF, ESR – 0.21Ω, deviation: 0%

C510: rated capacitance – 100uF, measured – 130uF, ESR – 0.23Ω, deviation: +30%

Pre module boards: A and B - mounted vertically on the tone control board

Pre module boards A and B (NA 06898-1) - before and after

The pre module board C has no electrolytic capacitors or noisy/trouble transistors. 

The pre module boards D and E are identical (NA 06898-3) and have six low leakage e-caps (C571 thru C574, C579, C580) installed in the signal path. All of them were replaced with modern low leakage Nichicon UKL caps.

Test results on original capacitors removed from the pre module boards D and E:

C571: rated capacitance – 10uF, measured – 8uF, ESR – 2.4Ω, deviation: -20%

C572: rated capacitance – 10uF, measured – 8uF, ESR – 2.2Ω, deviation: -20%

C573: rated capacitance – 10uF, measured – 8uF, ESR – 2.2Ω, deviation: -20%

C574: rated capacitance – 10uF, measured – 9uF, ESR – 2.2Ω, deviation: -10%

C579: rated capacitance – 22uF, measured – 21uF, ESR – 0.29Ω, deviation: -5%

C580: rated capacitance – 22uF, measured – 21uF, ESR – 0.71Ω, deviation: -5%

C571: rated capacitance – 10uF, measured – 8uF, ESR – 2.7Ω, deviation: -20%

C572: rated capacitance – 10uF, measured – 8uF, ESR – 2.6Ω, deviation: -20%

C573: rated capacitance – 10uF, measured – 9uF, ESR – 2.9Ω, deviation: -10%

C574: rated capacitance – 10uF, measured – 9uF, ESR – 2.6Ω, deviation: -10%

C579: rated capacitance – 22uF, measured – 20uF, ESR – 0.41Ω, deviation: -9%

C580: rated capacitance – 22uF, measured – 24uF, ESR – 0.42Ω, deviation: +9%

Pre module boards: C, D, and E - mounted vertically on the tone control board

Pre module boards D and E (NA 06898-3) - before and after

Tuner Board - 1

The phono equalizer circuit is a part of the tuner board - 1. This circuit has four low leakage e-caps installed in the input (C303, C304) and output (C327, C328) signal path, and eight aluminum electrolytic capacitors (C305, C306, C309, C310, C317, C318, C321, C322). All original low leakage e-caps were replaced with modern low leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with low impedance Nichicon UPW caps.

Test results on original capacitors removed from the phono equalizer circuit:

C303: rated capacitance – 10uF, measured – 8uF, ESR – 2.7Ω, deviation: -20%

C304: rated capacitance – 10uF, measured – 9uF, ESR – 2.4Ω, deviation: -10%

C305: rated capacitance – 2.2uF, measured – 2.1uF, ESR – 2.4Ω, deviation: -5%

C306: rated capacitance – 2.2uF, measured – 2.3uF, ESR – 1.9Ω, deviation: +5%

C309: rated capacitance – 220uF, measured – 218uF, ESR – 0.59Ω, deviation: -1%

C310: rated capacitance – 220uF, measured – 212uF, ESR – 0.62Ω, deviation: -4%

C317: rated capacitance – 470uF, measured – 531uF, ESR – 0.25Ω, deviation: +13%

C318: rated capacitance – 470uF, measured – 554uF, ESR – 0.32Ω, deviation: +18%

C321: rated capacitance – 100uF, measured – 103uF, ESR – 0.36Ω, deviation: +3%

C322: rated capacitance – 100uF, measured – 108uF, ESR – 0.52Ω, deviation: +8%

C327: rated capacitance – 10uF, measured – 9uF, ESR – 2.2Ω, deviation: -10%

C328: rated capacitance – 10uF, measured – 9uF, ESR – 2.6Ω, deviation: -10%

Phono equalizer circuit - before and after

Main Board

The main board has one low leakage capacitor (C601) installed in the signal path and four aluminum e-caps (C605, C613, C614, C615). The original low leakage e-cap was replaced with modern low leakage Nichicon UKL cap. The remaining aluminum e-caps were replaced with low impedance Nichicon UPW/UPM caps.

Test results on original capacitors removed from the main board:

Left channel:

C601: rated capacitance – 10uF, measured – 8uF, ESR – 2.1Ω, deviation: -20%

C605: rated capacitance – 220uF, measured – 227uF, ESR – 0.32Ω, deviation: +3%

C613: rated capacitance – 10uF, measured – 12uF, ESR – 1.62Ω, deviation: +20%

C614: rated capacitance – 47uF, measured – 52uF, ESR – 0.11Ω, deviation: +11%

C615: rated capacitance – 100uF, measured – 109uF, ESR – 0.18Ω, deviation: +9%

Right channel:

C601: rated capacitance – 10uF, measured – 9uF, ESR – 2.7Ω, deviation: -10%

C605: rated capacitance – 220uF, measured – 221uF, ESR – 0.54Ω, deviation: 0%

C613: rated capacitance – 10uF, measured – 13uF, ESR – 1.55Ω, deviation: +30%

C614: rated capacitance – 47uF, measured – 54uF, ESR – 0.32Ω, deviation: +15%

C615: rated capacitance – 100uF, measured – 107uF, ESR – 0.13Ω, deviation: +7%

The original trimming resistors VR601 (4.7Ω/0.5W, x2) were replaced with new Bourns potentiometers.

All power transistors were removed from the heat sink, cleaned, and tested. The measured DC current gain was in spec according to the datasheet. I applied a fresh thermal compound and replaced the old thermal pads with new Mica ones.

Main board - before and after (left and right boards are identical)

Dial and Meter Lamps

Three meters in the CR-1020 are illuminated with four incandescent lamps. Two of them were burned out. I replaced all of them with new incandescent lamps.

There is no backlit to the dial scale in CR-1020 but the dial pointer is illuminated. And unlike many other vintage receivers, it's relatively easy to replace the burned pointer bulb on this model. One just needs to unscrew two small screws on the top of the dial pointer unit and the lamp will be released.

Original dial pointer lamp - disassembled from the holder

A new lamp was installed

Bias Adjustment

The Bias is measured across the emitter resistor R631 (0.47Ω, 5W). The voltmeter should be connected between pins TP1 and 0 on the main board. The Bias should be adjusted to ~10mV with the trimming resistor VR601. It corresponds to the idling current of ~21mA (=10mV/0.47Ω).

Bias on the left and right channels after restoration

Power Meter Adjustment

An AC voltmeter and function generator are required to adjust power meters. A sine-wave signal of 1 kHz should be applied to the AUX terminals and the level of this signal should be adjusted so that the voltage on the SPEAKERS terminals read 20 VRMS. Then, the trimming resistors VR701 and VR702 should be adjusted so that the power meters read 50W.

Output Power Test

The final output power test was performed at the end of my restoration. The amplifier was loaded with a low inductance 8Ω/100W dummy resistor for each channel. The oscilloscope was connected across the speaker terminals and a sine-wave signal of 1kHz was applied to the AUX jacks. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 23.96 VRMS (left channel) and 24.17 VRMS (right channel). It corresponds to the output power of 71.8W on the left channel and 73.0W on the right channel.

Output power test

As usual, all the knobs and the front panel were gently cleaned in warm water with dish soap. All controls have been cleaned with DeoxIT 5% contact cleaner and lubricated with DeoxIT FaderLube 5% spray. The wood case was stained with Howard's Restor-A-Finish.

The final result can be seen in the photos below. The receiver looks brand new again and sounds fantastic! Please watch a short demo video at the end of this post. Thank you for reading.

Yamaha CR-1020 - after restoration

Demo video after repair & restoration