Sansui 9090 Receiver
The Sansui 9090 was released from 1975 to 1977 as a larger 8080 variant and remains an extremely popular Sansui today. Excellent rated performance and integration of the early BA312 made it a step above move available at the time and standard Sansui features such as the triple tone controls.
Power Supply F2546
The 9090 power supply assembly contains a full-wave bridge 5A for the 61 volt -/+ B supplies as well as a single full-wave for a 1A single ended 36 volt supply.
The full-wave bridge device was replaced with a common cathode ultra-fast, soft recovery MUR OnSemi type TO-220 device. The TO-220 regulator was replaced with a robust, modern OnSemi and coupled with synthetic Wakefield thermal compound. All small signal devices were replaced with low noise TO-92L Fairchild type for better dissipation. The electrolytics were replaced with a high temp (105C) low impedance and VP Bipolar Nichicon capacitors with an increase in operating voltages.
BEFORE
AFTER
Filter Capacitors
The two 6800MFD filter capacitors for the B-/+ supplies were both replaced with a computer grade CDE type.
-/+B Supply Confirmation
Protection F2547
The protection assembly involves a DC deviation and thermal cascade protection. This board also contains components for the LED’s, often times R12 appears to suffer cracking and will no longer operate correctly. The meter calibration circuit operates here as well.
All of the fusible resistors in this stage were replaced with KOA equivalents and the R12 resistors increased in current capacity with a MOX type. New ultra-fast, soft recovery axial Vishay diodes were installed. The meter calibrating potentiometers were replaced with Bourns precision type.
Electrolytics were replaced with a low impedance PW and VP Bipolar Nichicon capacitors with an increase in operating voltages. Films were replaced with a high-grade WIMA polypropylene film.
BEFORE
AFTER
Pre-Amp F2544 W/ BA312 Upgrade & Tone MIC Amp F2543
For the pre-amp stage were proud to offer the BA312 Upgrade we assisted in designing and now available online. The BA312 Upgrade offers a substantial improvement to the original “pre-amplifier” IC, with a modern Class-A fully discrete Op-Amp..the results are significant to say the least.
Two new BA312 Upgrade Modules with the Sparko’s Labs SS3601 Op-Amp are installed per channel. Electrolytics were replaced with a audio grade Nichicon KT/KA and low impedance Nichicon PW type with an increase in operating voltages. DC filtering stages were increased in overall capacitance. New high-grade WIMA polypropylene film capacitors were also installed. The secondary gain stage devices were replaced with a low noise, modern TO-92 type Fairchild devices.
BEFORE
AFTER
Mic Amp F2543 & Filter Switching
Similar to the 9090DB the 9090 features a BA312 central Mic Amplifier stage.
The F2543 requires the change of two resistor values due to the increase in current consumption of the BA312 modules. The electrolytics were replaced with low impedance PW and KT/KA audio grade Nichicons with an increase in operating voltages. The single small signal device was replaced with a low noise modern TO-92 Fairchild device.
BEFORE
AFTER
On the filter switch assembly both electrolytic capacitors were replaced with a audio grade KT/KA Nichicon capacitors.
BEFORE
AFTER
RIAA EQ F2541
Like the 9090DB the 9090 RIAA EQ stages features another BA312 in the RIAA EQ stage. Upgrades for the 9090 RIAA EQ are hopefully coming in the future but the current design produces quite the impressive curve and a solid improvement over most of the NPN/PNP stages available at the time.
Electrolytics were replaced with a audio grade KT/KA and low impedance PW Nichicon capacitors with an increase in operating voltages. New high-grade WIMA polypropylene film capacitors were installed.
BEFORE
AFTER
RIAA Curve Response
Drivers F2463
The 9090 output stage differs quite a bit from the 9090DB version, featuring a PP complimentary output and gain differential stage.
New precision matched differential pair transistors were installed with modern, low noise TO-92 Fairchild type. new pre-drivers were installed with low noise, TO-126 type Fairchild devices. VD series diodes were replaced with a modern axial 4148 series type. All fusible resistors were replaced with carbon film type and precision Bourns potentiometers installed.
Electrolytic capacitors were replaced with a low impedance PW, high temp (105C) and Bipolar VP Nichicon capacitors with an increase in operating voltages. New high-grade WIMA polypropylene film capacitors were installed.
BEFORE
AFTER
Bias Confirmation
RF
The nice part about the front end of the 9090/DB series is that the chassis completely lifts off for easy access to the RF front end and AF stages. The RF stage utilizes its own regulated 12.5V power supply from the 36+ single end supply.
The TO-220 regulator was replaced with a modern, robust OnSemi type device and coupled with synthetic Wakefield thermal compound. A new axial Vishay ultra-fast soft recovery diode installed as well. Electrolytic capacitors were replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages.
BEFORE
AFTER
BEFORE RF PS Stage
AFTER RF PS Stage
LEDs
New 8V custom multi-SMD LED type lamps were installed in both display and meter assemblies. The wiring for the selector switch is modified to re-route the AC source from the selector due to possible long term damage and arching.
AUDIO NOTIZEN
Cool! The RF stage utilizes its own regulated 12.5V power supply from the 36+ single end supply.
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