Pioneer SX-1010 Receiver
The Pioneer SX-1010 was released during 1974 thru 1976, as one of Pioneers last black/blue face receivers with the design intent of entry top-of-the-line models breaching 100Watts. The SX-1010 has some excellent design approaches such as robust power supply filtering and RIAA shielding and features such as dual phono inputs and a control stage defeat or twin tone adjustments.
POWER SUPPLY AWR-054
Like many Pioneer power supplies, wether it be a SA or SX series, has some faults within the power supply by using too small of regulator devices and small current limiting/Vf resistors which tend to cause PCB heating issues apparent on the substrate. The AWR-054 uses a series of a two full-wave bridge rectifier, full wave and 1/2 wave rectifiers.
The Full Wave Bridge rectifier was replaced and rerouted with our custom AC/DC rectifier modification employing Ultra-Fast, Soft Recovery Vishay diodes. The full wave and 1/2 wave were also replaced with like Vishay devices and bypass capacitors replaced with high grade WIMA polypropylene film capacitors. The 1/2 wave decoupling capacitors were increased to 3300MFD for a quite rail.
The electrolytic capacitors were all replaced with a high temp (105C) and low impedance Nichcion PW and Panasonic FC capacitor with an increase in operating voltages. Several heat prone resistors were replaced with a high wattage 1/2+ carbon film resistors. All three TO-220 regulators were replaced with a more robust, heavy duty TIP device with new performance Wakefield synthetic thermal compound.
BEFORE
AFTER
New 18,000/75V computer grade Nippon Chem/Con filter capacitors were added with the coupled 5W resistor.
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AFTER
PROTECTION AWM-062
The protection utilized int he SX-1010 is similar to a few other smaller SX series in design and function; With a built in current limiting circuit and Dc deviation detection as standard. A Muting On/Off feature is also featured.
All of the electrolytic capacitors were replaced with a high temp (105C) and low impedance Nichcion PW and Panasonic FC capacitor with an increase in operating voltages. A fly-back safety diode was added to the circuit to help prevent potential output damage. All of the small signal/trigger devices were replaced with new Fairchild TO-92/L and TO-126 devices for better dissipation.
BEFORE
AFTER
DRIVERS (AMP) AWH-032
The Driver design in the SX-1010 I much prefer, using separate PCB’s for each channel always performs better with a quieter noise floor. The drivers use a solid aluminum heatsink for both shared devices and the output has a unique cut-off. Due to the load output design when all three A/B/C speakers are utilized the impedance will more than likely drop below 4 ohms.
Differential Pair Matching
The initial PNP differential pairs were matched within 1% and paired along with the constant current source PNP with new low noise TO-92 Fairchild devices. The secondary pre-driver differential stage and current source were also replaced with new low noise, more robust TO-92 and TO-126 Fairchild devices. The bias adjustment was also replaced with a precision Bourns potentiometer. All new Ultra-Fast, Soft Recovery axial Vishay diodes were installed as well replacing the 247# series.
All of the electrolytic were replaced with a Nichicon PW low impedance and high (105C) series capacitors with an increase in operating voltages. All of the films were replaced with a high grade WIMA polypropylene and Panasonic ECW film capacitors.
Bias Confirmation @ 50mV-/+
CONTROL AMP (PRE) AWG-027
The SX-1010 uses a PNP/NPN direct coupled tiered stage with a high impedance input and direct coupled output with twin tone controls.
All of the small signal devices were replaced with a low noise modern TO-92 Fairchild devices. All of the capacitor and tantalum capacitors were replaced with a premium-audio grade and low impedance Nichicon KA/KT capacitors with an increase in operating voltages. The couplings were replaced with a high grade WIMA polypropylene film capacitors.
BEFORE
AFTER
RIAA EQ (PHONO) AWF-013
The phono stage is three stage direct-coupled RIAA stage with a independent differential stage employing a -/+ rail source. The RIAA stage itself is shielding from the perpendicularly mounted driver stage.
All of the small signal devices were replaced with a low noise modern TO-92 Fairchild devices. All of the capacitor and tantalum capacitors were replaced with a premium-audio grade and low impedance Nichicon KA/KT capacitors with an increase in operating voltages. The 0.22MFD coupling was replaced with a high grade MKP Solen polypropylene film capacitor.
BEFORE
AFTER
RF(AM/FM) AWE-040 & Muting AWM-039
The RF Muting circuit and entire FM/AM AWE-040 assembly capacitors were all replaced with applicable audio grade KT and low impedance PW Nichicon capacitors with an increase in operating voltages.
HARDWARE
New custom SMD LED’s were installed in both display and the meter display assemblies. A new smoothing 220MFD Nichicon PW low impedance capacitor was also installed. The dimmer switch was heavily cleaned and worked to prevent arching as is common with these.
Audio Notizen
