Pioneer SX-880 Receiver Restoration

Unit: AM/FM Stereo Receiver

Manufacturer: Pioneer

Model: SX-880

SN: YE3608705S

After restoring another Pioneer SX-880, I decided to update this post with improved photos and more detailed information about the restoration process for this classic receiver. These additions offer a more comprehensive overview of the work required to restore the unit to its original specifications and appearance.

The SX-880 model is the "big brother" of the Pioneer SX-780. The unit delivers 60 watts per channel into an 8-ohm load with a total harmonic distortion of no more than 0.05%. It was manufactured between 1978 and 1979. In 1978, its retail price was $425.

According to the Pioneer database, this specific unit was manufactured in May 1978.

AF Amplifier Board GWK-119

Power Supply Circuit

The power supply circuit has 10 aluminum electrolytic capacitors: C407, C408, C409, C410, C413, C414, C420, C421, C422, and C423.

All of them were replaced with Nichicon UPW/UPM low-impedance capacitors. Those e-caps are designed for switching power supplies and can operate in the temperature range from -55 to +105 C.

I discovered an error in the schematic related to electrolytic capacitor C410. The schematic specifies a 100uF/16V capacitor, while the original component installed on the board is actually 220uF/16V. This discrepancy was most likely the result of a design revision that was not reflected in the published documentation. I replaced the original capacitor with a Nichicon UPM low-impedance 220uF/25V capacitor.

The original e-caps were tested with an Atlas ESR70 capacitance meter; the results are below.

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

C407: rated capacitance – 470uF, measured – 379uF, ESR – 2.2Ω, deviation: -19%

C408: rated capacitance – 330uF, measured – 309uF, ESR – 1.1Ω, deviation: -6%

C409: rated capacitance – 100uF, measured – 106uF, ESR – 4.2Ω, deviation: +6%

C410: rated capacitance – 220uF, measured – 141uF, ESR – 1.6Ω, deviation: -36%

C413: rated capacitance – 3.3uF, measured – 4.1uF, ESR – 2.6Ω, deviation: +24%

C414: rated capacitance – 3.3uF, measured – 4.3uF, ESR – 3.5Ω, deviation: +30%

C420: rated capacitance – 47uF, measured – 37uF, ESR – 5.6Ω, deviation: -21%

C421: rated capacitance – 47uF, measured – 38uF, ESR – 3.5Ω, deviation: -19%

C422: rated capacitance – 100uF, measured – 100uF, ESR – 0.9Ω, deviation: 0%

C423: rated capacitance – 100uF, measured – 91uF, ESR – 0.8Ω, deviation: -9%

Three transistors (Q26, Q27, Q30) in the power supply circuit are running very hot under normal working conditions. Those transistors are mounted on heat sinks, but the size of each heat sink is not enough to efficiently dissipate the heat. If you plan to service this model, carefully inspect the PCB surrounding these transistors for evidence of overheating, such as discoloration or damaged traces. Also, be aware that the heat sinks are electrically live and should be treated with caution during troubleshooting and repair.

The original transistors installed in positions Q26 and Q30 were replaced with Onsemi KSC2073TU transistors. The original transistor installed in position Q27 was replaced with an Onsemi KSA940TU transistor. A new silicone thermal compound (Wakefield-Vette, 120 series) was applied between each transistor and the heat sink.

Protection Circuit

The protection circuit has 2 solid tantalum capacitors (C415, C416) and 3 aluminum electrolytic capacitors (C417, C418, C419). 

The original solid tantalum capacitors were replaced with Kemet film polyester caps. The remaining capacitors were replaced with Nichicon UPW low-impedance capacitors.

Test results on original capacitors removed from the protection circuit:

C415: rated capacitance – 0.22uF, measured – 0.22uF, ESR – N/A, deviation: 0%

C416: rated capacitance – 0.22uF, measured – 0.23uF, ESR – N/A, deviation: +5%

C417: rated capacitance – 33uF, measured – 34uF, ESR – 3.2Ω, deviation: +3%

C418: rated capacitance – 47uF, measured – 54uF, ESR – 2.1Ω, deviation: +15%

C419: rated capacitance – 10uF, measured – 13uF, ESR – 2.4Ω, deviation: +30%

The original relay driver transistor installed at position Q37 is a 2SC1885. Although this transistor is not known to be particularly failure-prone, I chose to replace it proactively with a Fairchild KSC2690 to improve the long-term reliability of the protection circuit. The KSC2690 has the same pinout as the original transistor, making it a direct replacement.

Control Section

The control section has 8 low-leakage capacitors (C205, C206, C217, C218, C227, C228, C229, C230) installed in the signal path, and 4 aluminum electrolytic capacitors (C209, C210, C215, C216).

The original low-leakage capacitors (C205, C206, C229, C230) were replaced with WIMA and Kemet film polyester caps. The other low-leakage capacitors (C217, C218, C227, C228) were replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with Nichicon UPW low-impedance capacitors.

Test results on original capacitors removed from the control section:

C205: rated capacitance – 1uF, measured – 1.1uF, ESR – 6.4Ω, deviation: +10%

C206: rated capacitance – 1uF, measured – 1.0uF, ESR – 7.2Ω, deviation: 0%

C209: rated capacitance – 47uF, measured – 58uF, ESR – 2.9Ω, deviation: +23%

C210: rated capacitance – 47uF, measured – 54uF, ESR – 3.7Ω, deviation: +15%

C215: rated capacitance – 100uF, measured – 122uF, ESR – 4.1Ω, deviation: +22%

C216: rated capacitance – 100uF, measured – 109uF, ESR – 3.2Ω, deviation: +9%

C217: rated capacitance – 4.7uF, measured – 6.7uF, ESR – 7.2Ω, deviation: +43%

C218: rated capacitance – 4.7uF, measured – 6.9uF, ESR – 6.7Ω, deviation: +47%

C227: rated capacitance – 2.2uF, measured – 2.6uF, ESR – 5.3Ω, deviation: +18%

C228: rated capacitance – 2.2uF, measured – 2.4uF, ESR – 5.2Ω, deviation: +9%

C229: rated capacitance – 0.22uF, measured – 0.21uF, ESR – N/A, deviation: -5%

C230: rated capacitance – 0.22uF, measured – 0.21uF, ESR – N/A, deviation: -5%

Phono Amplifier Circuit

The phono amplifier circuit has 4 low-leakage capacitors (C101, C102, C115, C116) installed in the signal path, and 4 aluminum electrolytic capacitors (C105, C106, C119, C120). 

All original low-leakage capacitors were replaced with modern low-leakage Nichicon UKL caps. The remaining aluminum e-caps were replaced with Nichicon UPW low-impedance capacitors.

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

C101: rated capacitance – 2.2uF, measured – 2.6uF, ESR – 4.8Ω, deviation: +18%

C102: rated capacitance – 2.2uF, measured – 2.5uF, ESR – 5.4Ω, deviation: +14%

C105: rated capacitance – 470uF, measured – 637uF, ESR – 4.8Ω, deviation: +36%

C106: rated capacitance – 470uF, measured – 608uF, ESR – 2.7Ω, deviation: +29%

C115: rated capacitance – 2.2uF, measured – 2.3uF, ESR – 2.6Ω, deviation: +5%

C116: rated capacitance – 2.2uF, measured – 2.4uF, ESR – 3.2Ω, deviation: +9%

C119: rated capacitance – 100uF, measured – 113uF, ESR – 4.1Ω, deviation: +13%

C120: rated capacitance – 100uF, measured – 115uF, ESR – 2.4Ω, deviation: +15%

FM Muting Circuit

The FM muting circuit has two low-leakage capacitors (C302, C303) and 3 aluminum electrolytic capacitors (C301, C304, C305).

All original capacitors in this circuit, except C301, were replaced with WIMA film polyester capacitors. The original capacitor C301 was replaced with a Nichicon UPW low-impedance capacitor.

Test results on original capacitors removed from the FM muting circuit:

C301: rated capacitance – 10uF, measured – 14uF, ESR – 1.9Ω, deviation: +40%

C302: rated capacitance – 0.47uF, measured – 0.61uF, ESR – N/A, deviation: +30%

C303: rated capacitance – 0.47uF, measured – 0.58uF, ESR – N/A, deviation: +23%

C304: rated capacitance – 0.47uF, measured – 0.62uF, ESR – N/A, deviation: +32%

C305: rated capacitance – 0.47uF, measured – 0.65uF, ESR – N/A, deviation: +38%

The original capacitor C402 installed across meter leads was replaced with a Nichicon UPW low-impedance capacitor.

Finally, the original protection relay was also replaced with a new Omron relay to improve overall reliability.

AF amplifier board - before and after

Meter Assembly Board (GWX-193)

The meter assembly board is secured to the chassis with three plastic retaining clips. Because access is limited, servicing the board is difficult unless it is removed from the chassis. I carefully released the clips using two small flat-blade screwdrivers. Since the clips have become brittle with age, they can break easily, so take your time and work slowly when removing them.

The board contains only 4 aluminum electrolytic capacitors (C501, C502, C503, C504), all of which were replaced with Nichicon UPW low-impedance capacitors.

Test results on original capacitors removed from the meter assembly board:

C501: rated capacitance – 4.7uF, measured – 6.5uF, ESR – 2.5Ω, deviation: +38%

C502: rated capacitance – 4.7uF, measured – 6.4uF, ESR – 2.7Ω, deviation: +36%

C503: rated capacitance – 4.7uF, measured – 6.4uF, ESR – 2.7Ω, deviation: +36%

C504: rated capacitance – 4.7uF, measured – 6.3uF, ESR – 2.4Ω, deviation: +34%

Meter assembly board - before and after

Tuner Board (AWE-099)

Be aware that replacing the original capacitors in the tuner section may require subsequent tuner alignment. I do not recommend servicing the tuner section of any vintage receiver unless you have all the necessary equipment and sufficient experience in tuner alignment.

The tuner board has one solid tantalum capacitor C37, two low-leakage capacitors (C38, C40), and 14 aluminum electrolytic capacitors (C27, C28, C34, C35, C41, C43, C44, C53, C60, C61, C67, C71, C72, C76). An additional axial electrolytic capacitor is soldered on the foil side between pin 22 and the negative lead of e-cap C76.

The original low-leakage capacitors C38 and C40 were replaced with WIMA film polyester caps. The original solid tantalum capacitor C37 was replaced with a new low-leakage Nichicon UKL cap. Two ordinary aluminum e-caps (C34, C41) with a nominal capacitance of 1uF were replaced with WIMA film polyester caps. The original axial e-cap was replaced with a new Vishay (138 AML series) capacitor. The remaining capacitors were replaced with Nichicon UPW low-impedance capacitors.

Test results on original capacitors removed from the tuner board:

C27: rated capacitance – 2.2uF, measured – 2.7uF, ESR – 2.8Ω, deviation: +23%

C28: rated capacitance – 4.7uF, measured – 6.8uF, ESR – 2.4Ω, deviation: +45%

C34: rated capacitance – 1uF, measured – 1.5uF, ESR – 2.2Ω, deviation: +50%

C35: rated capacitance – 22uF, measured – 28uF, ESR – 2.1Ω, deviation: +27%

C37: rated capacitance – 6.8uF, measured – 7.4uF, ESR – 1.8Ω, deviation: +9%

C38: rated capacitance – 1uF, measured – 1.2uF, ESR – 5.9Ω, deviation: +20%

C40: rated capacitance – 1uF, measured – 1.2uF, ESR – 6.6Ω, deviation: +20%

C41: rated capacitance – 1uF, measured – 1.5uF, ESR – 2.1Ω, deviation: +50%

C43: rated capacitance – 330uF, measured – 376uF, ESR – 0.9Ω, deviation: +14%

C44: rated capacitance – 220uF, measured – 144uF, ESR – 0.9Ω, deviation: -35%

C53: rated capacitance – 220uF, measured – 151uF, ESR – 1.9Ω, deviation: -31%

C60: rated capacitance – 4.7uF, measured – 6.6uF, ESR – 2.9Ω, deviation: +40%

C61: rated capacitance – 3.3uF, measured – 4.3uF, ESR – 2.8Ω, deviation: +30%

C67: rated capacitance – 22uF, measured – 29uF, ESR – 1.8Ω, deviation: +32%

C71: rated capacitance – 10uF, measured – 13uF, ESR – 2.4Ω, deviation: +30%

C72: rated capacitance – 10uF, measured – 13uF, ESR – 2.8Ω, deviation: +30%

C76: rated capacitance – 10uF, measured – 13uF, ESR – 1.9Ω, deviation: +30%

C# (axial cap): rated capacitance – 10uF, measured – 11, ESR – 2.2Ω, deviation: +10%

The original 2SA726 transistor in positions Q7 and Q8 is notorious for its shot noise. I replaced it with a modern low-noise Fairchild KSA992 transistor. See the pinout for the replacement transistors. The original transistor is BCE, and the new one is ECB. Also, make sure that the new transistors are gain-matched (note the blue dots on the original transistors).

Additional axial e-cap soldered on the foil side - before and after

Tuner board - before and after

Main Filter Capacitors

Both main filter capacitors were tested using an Atlas ESR70 capacitance meter. The measurements showed that both capacitors were still within the original factory capacitance tolerance and exhibited low ESR. Based on my experience, the main filter capacitors in vintage audio equipment rarely fail, so I generally do not replace them unless they show elevated ESR or other signs of deterioration.

However, during a careful visual inspection, I discovered that one of the filter capacitors was leaking electrolyte, which had already caused minor corrosion on the chassis beneath it. Since this type of leakage can lead to further damage if left unaddressed, I replaced both filter capacitors with new Kemet capacitors (ALT22 series). The replacement capacitors have the same capacitance as the originals but feature a higher maximum voltage rating of 63 V.

Test results on the original filter capacitors:

C2: rated capacitance – 15000uF, measured – 13960uF, ESR – 1.2Ω, deviation: -7%

C3: rated capacitance – 15000uF, measured – 14380uF, ESR – 1.6Ω, deviation: -4%

Original filter capacitor - leaking electrolyte

New Kemet filter capacitors

Dial Lamps

As I mentioned in my previous restoration articles, I prefer to install new incandescent dial lamps in Pioneer SX-x50 and SX-x80 receivers. In my opinion, even modern warm white LED replacements alter the original appearance of these classic receivers.

To minimize the heat generated by the incandescent lamps, I applied a strip of aluminum foil tape to the inside of the top cover. The foil reflects light back toward the dial while also reducing the amount of heat transferred to the cover, helping to protect it from prolonged heat exposure.

Tip: there is a small opening at the center of each lamp socket. I used a small Allen wrench and gently pushed each lamp out of the socket. In that case, the brittle socket tabs won't be damaged or broken.

Push each dial lamp out of the socket with a small Allen wrench

DC Offset and Bias Adjustments

At the end of the restoration, I verified and adjusted the power amplifier's DC offset as described in the service manual. This adjustment does not require a dummy load or an input signal. The DC offset on both channels was adjusted as close to 0V as possible using trimmers VR5 and VR6.

Next, I checked and adjusted the bias. The bias voltage is measured between pins 8 and 10 on the left channel and between pins 14 and 16 on the right channel. Using trimmers VR7 (left channel) and VR8 (right channel), I adjusted the bias to approximately 30mV on each channel, as specified in the service manual.

DC offset on the left and right channels after restoration

Bias on the left and right channels after restoration

Power Meters Calibration

An AC voltmeter and function generator are required to calibrate 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 reads 21.9 VRMS. Then, the trimming resistors VR9 and VR10 should be adjusted so that the power meters read 60W.

Output Power Test

The final output power test was conducted at the end of the restoration. Two low-inductance 8Ω/100W resistors connected across each speaker terminal were used as a dummy load. The output sine-wave signal was perfectly symmetrical on both channels with no clipping up to 22.20 VRMS (left channel) and 22.09 VRMS (right channel). It corresponds to the output power of 61.6W on the left channel and 61.0W 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 final result can be seen in the photos below. The sound is wonderful, warm, and clear. Please watch a short demo video at the end of this post. Thank you for reading.

Pioneer SX-880 - after restoration

Demo video after repair & restoration