Sansui 9090 Receiver
Today we’re showing off a sansui 9090 that can in for a power supply, driver rebuild and testing.
The 9090 is an extremely poplar Sansui we get in for restorations along with the DB version. The major differences are the integration of the Dolby network, driver design and form factor and the a complimentary output vs the quasi output of the 9090.
F2546 Power Supply
The main PCB has the AF/Ax power supply as a main large PCB in the centre of the unit which also houses a PCB card slot for the driver to sit perpendicular to the F2546.
All of the electrolytic were replaced with high temp (105C) low impedance PW Nichicons with an increase in operating voltages including the 1000MFD capacitor. The BJT were all replaced with NPN KSC TO-92L Fairchild devices along with the TO-220 voltage regulator transistor and two ultra-fast 4007 diodes for a common cathode replacement.
One of the common issues on the 9090 is the fact that the AC lamps is ran through the selector switch as well which causes arching to occurring within the phenolic switch destroying it! This simple mod changes the pinout location keep the dial illuminated while the units is always on just like the 9090DB version and saves your expensive hard to find selector switch! New custom SMD type LED's were installed as well.
The driver assembly on many of the original 9090 and 9090db we get in exhibit the sam exact issues. heat damage and cascade failures from the original fusible resistor design. Typically someones been in there trying to fix it and mucks it up worse.
All of the fusible resistors as well as glue covered resistors were replaced with KOA carbon film type 1/2W as well as the epoxy diode VD1212 to modern 4148 type in series. All of the electrolytic were replaced with Nichicon high temp (105C) VP BiPolar/PW with an increase in operating voltages. The .47 input and .1 mylar were both replaced with high grade WIMA polypropylene film capacitors.
The TO-92 differential pair NPN were replaced with 1% matched beta low noise Fairchild TO-92 transistors and bias/ pre-drivers to modern low noise and robust TO-126 Fairchild transistors. Both sets of potentiometers were replaced with person Bourns devices. The TO-3s were removed and new compound applied as well. Often times Ill find fuses half assed soldered on this board which is cleaned up and presented better.
Cleaning Tone Assemblies
All of the original tone control boards were point inspect and cleaned for better operation and the PCB flushed with lab grade anhydrous alcohol