Lloyds Pioneer SX-1080 Receiver

Pioneer SX-1080 Receiver

Today Im showcasing a customers Pioneer SX-1080 Receiver restoration.  The SX-1080 is the updated brother to the Pioneer SX-1050, the 1080 was released  from 1978 to 1979, where as the 1050 was released from 1976 to 1977. The SX-1080 featured several changes from its equivalent brother the 1050. Two output meters were introduced along with a different facia scheme to black/lighter lettering. One speaker output was removed, additional turn over controls along with an increase in driver stage performance. The topology between the two units is quite similar though I would easily beg the SX-1080 is a step better. The SX-1050 uses a single symmetric driver stage where as the SX-1080 went with separate channels which of course is always better, decreasing intrinsic potentials. I should add the SX-1050 has a substantially better volume potentiometer build.  Both use a quality Toroidal transformer and 22,000MFd filter stages.

You can read up on the recent SX-1050 I restored here;

http://marantzhallo-fi.blogspot.com/2017/05/franks-pioneer-sx-1050-restoration.html

AWR-152 Power Supply & AC/DC Upgrade

AC/DC Upgrade

Power supplies are one of the most critical areas of a units operation, without a clean and stabile rail source the unit cannot perform optimally.  During this restoration particular attention was paid to significant upgrades done on the power supply.  Using todays modern components we can dramatically update the rectification stages for a MUCH more quite, cleaner and reliable AC/DC conversion. 

The SX-1080 uses two Full Wave Bridge rectifiers a 1A/10A for the -/+ 83V (schem error at 76V) rails and -/+ 62V via two 22,000MFD filter capacitors. an additional 1A Full Wave CT rectifiers establishes the 13/7.5V voltages. The Full Wave CT was replaced with two high-end Cree Schottky TO-220 Zero-Recovery receivers, with feature extremely fast switching, high freq. operation with zero forward/reverse voltage/current breakdown along with a high grade WIMA polypropylene film bypass capacitor.  The original 1A axial diode rectification bridge was replaced with an array of  modern On-Semi TO-220 MUR type Ultra-Fast, Soft recovery rectification devices, in additional to better, cleaner rectification devices the smoothing/reservoir capacitors were increased to 330MFD/100V and a new 2200MFD PW capacitor. Ive implemented this now into several Pioneer restoration with again….dramatic positive effect…the sound stage is dimensional along with a more defined and clean lower end presentation!

Ripple Voltage Comparison

On the Power Supply AWR-152 all of the electrolytic capacitors were replaced with a low impedance, high temp (105C) Nichicon PW and high temp Panasonic FC capacitors with an increase in operating voltages. All of the small signal devices were replaced with modern low noise, Fairchild TO-92L devices for better dissipation and new TO-220 high voltage regulators with new robust Fairchild devices and new lab grade WakeField thermal compound. 

BEFORE

AFTER

Filter Capacitors

Both original Nichicon 22,000MFD capacitors were replaced with new, computer grade Nippon Chem Con 22,000MFD/100V filter capacitor.

AWM-120 Protection/Inrush (soft start)

The soft start/inrush and protection stage is quite a bit more robust than the 1050, with a soft start 48V relay and 48V MY2 protection. The protect circuit employs a DC deviation/output, Overcurrent and Start Muting (Inrush limiter circuit)

The 48V relays were replaced with new Omron 48V MY series relays. Capacitors were replaced with new high temp (105C) low impedance Nichicon capacitors with an increase in operating voltages. New low noise TO-92L/TO-126 Fairchild devices were installed for better dissipation.

BEFORE

AFTER

GWS-124 Speaker Selector

The Selector PCB and Meter adjustment pcb controls the output calibration for the two meters, which is based off a signal logarithmic compression circuit.

Adjustments were replaced with high quality precision Bourns potentiometers along with a new low noise NPN TO-92 Fairchild device. New audio grade KT and Fine-Gold (FG) Nichicon capacitors were installed with an increase in operating voltages.

BEFORE

AFTER

AWH-071 Drivers (Recht/Links)

The power amplifier channels each have their own separate PCB versus the SX-1050 with a modular Heatsink tunnel between. The AWH-071 is comprised of a OCL (output capacitor less) direct coupled stage using a differential stage, constant current-pre-drivers and push-pull output compliment.

The dual differential device was replaced with two matched Hfe, low noise, modern Fairchild TO-92 devices. (mapped below) Remaining small signal/Predriver devices were replaced with a modern low noise/low distortion  Fairchild TO-92 and TO-126 devices. New Ultra-Fast.

Hfe Mapping

The original 2.2MFD electrolytic was replaced with a low impedance PW Nichicon capacitor to ground, all the original 1/.22MFD capacitors including mylar were replaced with a high grade WIMA polypropylene film capacitors.  The adjustments were replaced with a precision grade Bourns potentiometers. 

BEFORE

AFTER

Bias Confirmation

GWS-125 Function and RIAA EQ  

The Mic/RIAA stage uses a pair of HA1457 SIP devices, which is a dual rail -/+22V early pre-amplifier IC for the front end gain establisher. Due to the restriction of space/location a RIAA Curve response in DUT cannot be obtained, I should add the RIAA lacks any degree of shielding for its proximity to the RF stage and PS.

All of the electrolytic capacitors were replaced with a audio grade KT and Fine-Gold (FG), as well as low impedance PW Nichicon capacitors with an increase in operating voltages. The switching circuit NPN devices was replaced with a TO-92L modern low noise Fairchild device.

BEFORE

AFTER

GWG-112 Flat Amp, AWG-056 & AWT-001 AF Stages

The flat amp stage is a all-stage direct coupled Af stage employing two 2SK34 JFET devices. The proceeding Tone Amp AWG-056 has a NPN stage using a NFB designed circuit coupled to the AWT-001 additional adjustment. A turnover point and defeat functions are employed in the SX-1080.

In the Flat amp both PNP devices were replaced with low noise, modern TO-92 Fairchild devices. New high grade WIMA polypropylene films for the 1MFD> values were installed and new Fine-Gold (FG) and KT audio grade Nichicon capacitors with an increase in operating voltages. The volume potentiometer/balance etc were removed and treated with Caig-Labs D5 and F5 products.

BEFORE

AFTER

On the Tone Control stage, again both NPN devices were replaced with hlow noise, modern TO-92 Fairchild devices. The .02 mylar films were all replaced with a high grade WIMA polypropylene film capacitors as well as new audio grade Fine-Gold (FG) and KT Nichicon capacitors with an increase in operating voltages. 

BEFORE

AFTER

The filter switching stage had the original .47 and .01 mylar films all replaced with a high grade WIMA polypropylene film capacitors. 

BEFORE

AFTER

AWE-092 RF Stage

The AM/FM stages are built around a 2-stage variable tuning capacitor for the AM and  4-stage FM capacitor.

All of the electrolytic capacitors here were replaced with a high temp (105C) , low impedance Nichicon PW capacitor. The 1MFD> values were all replaced with high quality, extremely reliable WIMA polypropylene film capacitors. 

Hardware

New custom SMD LED’s installed for a reduction in radiant heat to minimize damage to the plastic shroud. 

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