Sansui 9090DB W/ BA312 Modifications
The Sansui 9090DB remains even today one of the most popular and sought after Sansui 100+ receivers. The Sansui 9090, 990 and DB version are all very similar designs with a few differences to note, the 9090 is rated at a nominal 110W vs the 9090DB @ 125W @ 1%THDN. The 9090DB also incorporates the Dolby staging as well as different MIC amp, and driver topology and output compliments.
In this restoration we are very very proud to release the full integration with our new BA312 Modifications. These revolutionary devices allow us to now replace the original monolithic linear silicon interated-circuit (IC encapsulated) device that is longer available with a adaptive circuit module and high performance Op-Amp only offered with our restorations world wide! You can read the detailed breakdown further down in the restoration outline!
F-2656 Power Supply W/ AC/DC Rectification Upgrade
The Power Supply for the Sansui 9090DB is built off two full wave CT bridge’ rectifiers with a .3A and 5A output for the DUT and drivers. One of the most significant upgrades I have been installing in these vintage units is the upgrade from the original axial silicon diodes to ultra-fast, soft recovery, low noise Schottky TO-220 mounted rectifier diodes on a high quality FR4 custom PCB. The power supply is the heart of the beast so to say, so the cleanest, most reliable and stabile voltage sources begin here and feed the rest of the unit thru deep dips such as with sub-sonic 10-50Hz responses at peak output without sagging or starving the amp. In addition to the upgraded rectifiers the DC filtering capacitors were increased to 1000MFD/470MFD for a cleaner rail source.
Confirmation of -/+ Rail source
The remaining electrolytic capacitors were replaced with a low impedance, high temp (105C) Nichcion PW and Bi-Polar Nichicon VP with an increased in operating voltages. The remaining TO-92 devices were all replaced with modern, low noise TO-92L Fairchild devices with better dissipation. The 1OHM Fusible resistor were all removed and replaced with MOX 1/2Watt resistors
The protection assembly on the Sansui 9090DB can be a bit of a trick to access, though once removing the top RF section of the chassis is much easier. The 9090DB features multiple protection factors such as two output coupled fuses, relay triggered DC devastation and thermal varistors as well as a inrush limiter.
After the top chassis is removed you can now access the protection
Like the Power Supply several Fusible 4.7OHm resistors are replaced with 1/2W carbon film KOA resistors. The MY3 was removed and replaced a with a Omron MY24V relay. All of the small signal devices were replaced with low noise modern TO-92 Fairchild devices as well as new axial silicon general diodes. All of the smaller coupling and 1MFD capacitors were replaced with a high grade WIMA polypropylene film capacitors as well as remaining electrolytic with a low impedance, high temp (105C) Nichcion PW and Bi-Polar Nichicon VP with an increased in operating voltages.
F-2653 RIAA EQ (PHONO) W/ BA312 Modification Installed
As part of our new exciting product releases we incorporate a BA312 to Op-Amp Modification. This replaces the original old monolithic, linear integrated-circuit (IC) device and replaces it with a custom adaptive module circuit board coupled with a high grade SS3601 fully discrete Op-Amp! The final product was installed reveals a significantly tighter RIAA Curve response especially at the subsonic 31.5Hz and high 15Kz sweep points compared to the stock BA312 creating an incredibly accurate RIAA EQ! We are the first and only company world offering this specialized upgrade option designed in conjunction with Sparko’s Labs. You can read more on the BA-312 kit upgrade option we offer at the link below with complete performance breakdowns!
In addition to our custom BA312 module installed, the two 470MFD DC filtering capacitors were increased to 1000MFD for a cleaner 40Vdc rail supply, as well as additional electrolytic with a audio grade Nichicon KT with an increase in operating voltages. The initial 47PF input was replaced with two high grade WIMA polypropylene film capacitors as well as C602 coupling to a WIMA PP film.
RIAA Curve Response Comparison
F-2544 Tone (Pre-Amp_ W/ BA312 Modification Installed
As part of our new exciting product releases we incorporate a BA312 to Op-Amp Modification. This replaces the original old monolithic, linear integrated-circuit (IC) device and replaces it with a custom adaptive module circuit board coupled with a high grade SS3601 fully discrete Op-Amp! The final output report details impressive enhancements with the BA312, not only is mid signal level distortion+noise dropped but overall IMD and Signal to Noise ratios were all decreased. The frequency response before lacked a high/subsonic response with a normal rated deviation of -1dB(yikes!) we are now able to secure that too -0.17 and 0.35dB response!! We are the first and only company world offering this specialized upgrade option designed in conjunction with Sparko’s Labs. You can read more on the BA-312 kit upgrade option we offer at the link below with complete performance breakdowns!
Due to current consumption of the new BA312 modules (still low at 15mA per), the supply rail located at the F-2617 MIC AMP board required changes with new 1/2 carbon film KOA resistors. In addition to our custom BA312 module installed and values within the remaining electrolytic capacitors were all replaced with a audio grade Nichicon KT and low impedance PW’s with an increase in operating voltages. High grade WIMA polypropylene input coupling films were installed as well. Both NPN devices were replaced with low noise, modern TO-92 Fairchild devices.
F-2617 MIC Amp + F-2626 Filter Assembly
The supply voltages for the F-2544 is sourced through several dropping resistors on this assembly which are adjusted. The original BA312 in this circuit remains as it is outside the DUT signal path and a little used feature by todays end users.
The tantrum capacitors and remaining electrolytic were replaced with a audio grade KT Nichicons with an increase in operating voltages. The NPN device were replaced with a modern, low noise TO-92 Fairchild.
The F-2626 filter assembly is coupled to the output of the F-2544 tone stage apply the hi/lo pass RC filter arrays and audio muting featuring. The two 2.2MFD input coupling capacitors were replaced with a audio grade Nichicon KT, with the remaining ceramic signal path to high grade WIMA polypropylene film capacitors.
F-2624 Driver Stage
The Sansui 9090DB driver has some fairly notorious failure rates due to the use of fusible resistors in the amplifier stages and thru-out. All of these were replaced with 1/2 carbon film resistors and is very crucial to avoid future failures. The driver topography differs greatly from the 9090, comprised of a complimentary output stage vs quasi on a symmetric single PCB. This unit had suffered leaking BJT TO-3 output compliments with a failed SVT thermistor diode causing a cascading bias initially which was repaired with new TO-3 NPN/PNP installed with performance Wakefield thermal compound.
All of the transistors on board were replaced, the differntial pairs were matched BETA as well as current sirocco, pre driver and driver compliments with modern, low noise and robust TO-220/126 and 92 Fairchild and OnSemi devices.
Differential Compliment BETA Matching
All adjustments were replaced with precision Bourns potentiometers as well as VD epoxy type diodes replaced with modern series axial Vishay diodes. Electrolytic capacitors were replaced with a low impedance high temp (105C) Nichicon PW with an increase in operating voltages as well as new high grade coupling .47MFD WIMA polypropylene film capacitors.
F-2619 RF Power Supply
The RF power supply uses an underrated regulator and over taxes the wire wounds. The TO-220 regulator was replaced with a robust, modern TO-220 OnSemi devices and associated devices to better dissipating TO-126 Fairchild devices. New low impedance high temp (105C) Nichicon PW capacitors with an increase in operating voltage were installed.
F-2655 Dolby NR + F-2654 Switch Assembly
The Dolby circuit int he 9090DB is one of the most problematic assemblies out there for Sansui, they often fail due to either electrolytic failure or often solder points at the thru-hole connections. On this model the shaft for the selector had actually extruding the first gang and had to be repaired as well as 75+ connection/solder points. All of the electrolytic capacitors and coupling were replaced with a high temp (105C) low impedance Nichicon PW with an increase in operating voltages as well as coupling/input .01/.33MFD to high grade WIMA polypropylene film capacitors installed.
The F-2654 Switch Assembly is coupled to the selector parallel to the Dolby PCB, a new 10MFD Nichicon PW capacitor was installed along with new coupling .047/.033 to high grade WIMA polypropylene film capacitors.
F-2549 Main RF
With the entire RF chassis separated access to the main F-2549 is easier, all of the tantalum and electrolytic capacitors here were replaced with a BiPolar and low impedance Nichicon VP and PW with an increase in operating voltages.
Meter Modification + LED Lamps
The original wheat lamps in the meter often fail from the leads oxidizing and corroding. By changing the dropping resistors to a 100OHM and using two 3.5Vf diodes in parallel we are able to use the existing PCB footprints for a long life (15,000hr) LED diodes.
Remaining Meter and Dial display 8V fuses lamps were all replaced with custom multi-sms Fuse LED’s.