Sansui G-22000 Pure Power Stereo Receiver

Sansui G-22000 Pure Power Stereo Receiver

I wanted to showcase a very special and somewhat rare Sansui restoration we’ve recently completed, a Sansui G-22000 Pure Power Stereo Receiver! Hailed, along with the G-33000 as one of the biggest receivers ever produced by Sansui.

The G-22000/33 were built with performance and versatility in mind, presenting with an impressive dynamic range of 0Hz-300,000Kz super sonic frequencies.  Using a DC or „Direct Coupled“ amplifier stage and proprietary „Diamond Differential DC circuit,“ the G22000/33 revolved around the capacitor-less topography concepts. Cosmetically designed to be the pinnacle of class and performance with grated noir look, the G-22000/33 are some of the best receivers ever produced in our opinion.

Power Supplies  F2902/F2903  & F2891

The G-22000 utilizes three different independent power supply circuits and three different power transformers.  The Front End (Pre-Tune reference)  with its own power supply network that is tethered as a protective/ Power cycle trigger via a patented umbilical cable.  Each of the driver stages involved its own high quality Toroidal Power Transformers with its own protect/power supply circuit, also coupled to a pair of 15,000MFD filter capacitors for a combine smoothing stage of 60,000MFD. The four filter capacitors were replaced with high quality Nippon Chem-Con 22,000MFD 100V capacitors for a total of 88,000 MicroFarads!

Each independent protection circuits use a rule of 4 detection paths including;  OverCurrent Detection,  Speaker Terminal Short Circuit Protection, Thermal Detection Relay Active and finally a DC Detection Protector circuit.    

Each 2902/2903 contain X2 relays as part of the 4way detection.  All the relays were replaced with new Low Noise Omron LY-2 (24V) relays.  Electrolytic’s were replaced with all Panasonic high temp (105C) FC capacitors and high temp, low impedance (105C) Nichicon PW capacitors.  The Power Supply assemblies contain a large number of 2473/10D1 type diodes which were all replaced with Ultra-Fast UF4005 and standard 4148 diodes.  Remaining MV12 glass pack diodes were replaced with 4148 type in series configuration.  Small Signal and Driver transistors were replaced, updating TR01/4  MJE15032/33 On Semi devices.  NPN 2071 and PNP 939 with MJE340/350 TO-220 transistors.

One of the most important issues to address with Sansui are the Fusible type resistors.   R1-40 selective were all replaced with flame proof Carbon Film 1/2W resistors.  Its very important to notate, on the G22000/33 their is a large inrush limiter resistor for the soft start relays,  when damage occurs or excessive current draw within the unit it can, and likely will stress and slew this large 25W resistor.  In this case some shop had replace the R701 with a 2.2OHM 25W  which had actually skewed its value to an impressive 11.9K OHMS causing the soft start delay to malfunction.  Each of the G2H-21XX soft start relay’s were disassembled and the contacts and spring cleaned.  

Driver Assemblies F2900/F2901

The G-22000 Driver assemblies  each contain a dual FET input differential circuit comprised of a 6leg JFET 2Sk129.  The second stage used the proprietary Diamond Differential designed by Susumu Takahashi and Tadaaki Chikashige of Sansui Electronic Co., LTD Tokyo first publish patent Aug 25th 1977.  The Diamond circuit is designed for a a-b balanced signal via congruently phased signals.  The 3rd order stage is made of a mirror-current and Push-Pull drive design. to a tie  NPN/PNP darlington-Push Pull configuration. (G33000 total PP W/ 8 TO-3 Outputs) The TO-3 output sections were removed and inspected and cleaned thoroughly with noted SIL pads installed.

All of the large 220MFD capacitors were replaced with a low impedance Nichicon PW capacitor, Differential couplings were updated with Nichicon KA audio grade capacitors and FG audio grade and Polypropylene WIMA’s films for the remained.  The coupled .47MFD films were upgraded to MKP polypropylene film capacitors and as above in the PS the MV type Glass pack MV-103 diodes to series (x3) 4148 type standards.   The DC/ Bias potentiometers were updated to precision Bourns trimmers and the remaining Fusible type resistors replaced with 1/2W carbon film KOA resistors. 

All of the small signal transistors were replaced short of the JFET.  2071/939 type small signal transistors were updated to pairs of MJE340/350 type and the 3rd drivers with MJE15032/33 On Semi TO-220 heavy duty transistors with new thermal compound applied.  The remaining 872/1775 transistors were matched to 1% replaced with KSA992/KSC1845 type. 

AF STAGES F2890/F2899 Flat Amp-Tone 

The Tone amp and Flat amp stages comprise a single symmetric PCB and F-2899 as two separate symmetric assemblies mounted via connectors to the underside of the chassis.  

On the F2890 assembly all of the electrolytic were replaced with audio grade Nichicon KA BiPolar VP Nichicons.  The coupled films were replaced with .1MFD high grade WIMA polypropylene film capacitors.  The small signal TO-92 872 transistors were replaced with 992 type and the TO-220 2071 with MJE340 type.

F2899 symmetric assemblies involve again the 2SK129 differential JFET nun gain stage with an apparent significant slew rate.   Like the above Af assemblies Nichicon audio grade KA and FG were installed along with the .22MFD coupling film to a MKP high grade polypropylene film capacitor.  The remaining 2473 diodes were replaced with standard 4148 type and 872 compliments to 992 type TO-92 transistors.

A few miscellaneous items to cover such as installing new power cords 

and a shot of all the 250+ components replaced over the 25 hours it took to rebuild and tests;

Audio Notizen

EQ STAGES  F2880/F2884  RIAA/Motherboard

The EQ (Phono) stage is touted with a again a 2Sk131 Dual JFET bootstrapping current array following a non gain stage and ending with SEPP (single-ended Push Pull) stage.

Like the above AF assemblies the electrolytic were replaced with a audio grade Nichicon KA. The large 5MFD coupling film was replaced with a high grade MKP polypropylene film capacitor.  The remaining 2473 updated with standard 4148 diode and the 872 small signal transistors updated to 992 type.  

The F2884 Motherboard assembly had both large electrolytic replaced with low impedance, high temp (105C) Nichicon PW’s and the coupling films with high grade .47 polypropylene film capacitors

RF Tuner F2920

The G-22000/33 has an incredibly impressive RF stage. With a linear tuning 5-Gang tuning capacitor and Dual MOSFET driver designs allow for solid pick up even in hostile enviroments, with distortion limiting circuits and Wide/Narrow and advanced Muting/Noise filters this is one of the better RF sections I’ve seen. We replaced all of the tantalum and electrolytic with low impedance, high temp varaint (105C) Nichicon PW capacitors and Bipolar Vp capacitors. .1MFD BP was replaced with a Panasonic ECQ film capacitor. The tuning capacitor was dusted, cleaned and the points shaft location contacts cleaned. 

Meter & Volume Assembly Assemblies F2886/F2892

Remaining Stages as F2886 Volume/Mic Amp PCB’s had the remaining electrolytic with audio grade Nichicon FG and low impedance Nichicon PW’s.  The volume potentiometer on the G-22000 is an impressive calibrated 4 Gang 32- stepped attenuator!

Along with the F2892 Peak Meter assembly with Nichicon PW capacitors.  Sansui express these as professional series outer magnet Meters responsive from .1-600 Watts Pkv

F2885 Mic First Amp PCB was repopulated with high grade WIMA polypropylene film capacitors and a single audio grade Nichicon KA along with a updated KSA992 small signal transistor. The 

F2906 output circuit PCB with a updated 10D1 to UF4005 diode and two high grade WIMA polypropylene film capacitors.

As each stage was removed all the contacts and switches were deeply flushed, cleaned and then lubricated. Including the fan assembly with a light touch of 3:1 and thoroughly cleaned of dust and potential matter and cleaned with lab grade anhydrous alcohol. Some shop before had replace for some unknown reason the Front End unit AC Cord with a Polar AC cord....the G-22000 Driver section has a BiPolar AC receptacle installed in the chassis so why someone did that is beyond me. The replaced cord was removed and a UL grade BiPolar cord installed…

Audio Notizen

As we can see the performance parameters of the G-22000 is damn impressive!