Monday, September 12, 2016

Sansui 990 Receiver Rebuild

Sansui 990 Receiver 

Today were showing off a Sansui 990 Receiver that came in for a focused restoration the European Multi-Voltage version of the Sansui 9090 Receiver. Featuring multiple hi level inputs and a trifecta tone control plus a combination A,B and C speaker options.

Power Supply F2546 & Protection F2547
Like many of the G-series, the 9090/990 utilizes a large main power supply pcbs also populated with rectification stage. All of the electrolytic on this PCB were replaced with high temp (105C) long life Nichicon PW/KL along with the regulating TO-220 to a modern MJE1503# transistor.  Four BiPolar electrolytic populate the under chassis which were re-oriented and replaced with VP Nichicons.  

Unlike the other latter db series the protection is actually decently accessible on this series.  The original MY4 relay was replaced with a low noise Omron MY4 type.  The Bi-Polar electrolytic were replaced with a high grade polypropylene WIMA film and VP Nichicon. Remaining electrolytic were replaced with a long life, low impedance PW’s. Often times i will find the R12 resistor cracked which is replaced with a carbon film vishay 1/2W.  The 2SC945 was replaced with a 945 TO-92 BJT.  New Nichicon 6800MFD electrolytic were installed and bypassed.

The selector and rails for lamping are also populated on the RIAA EQ PCB.  Like several era similar receivers the RIAA uses a BA312 class a gain IC for the initial stage.  All of the electrolytic’s were replaced audio grade KA and low impedance PW Nichicons as well as the C901 to a 1MFD high grade polypropylene film capacitor. 

Tone Controls/Amp F2543 & F2544
The tone amp, as above uses a class a IC (pre-amp IC) BA312 for the initial gain stage like the Marantz 2325 Receiver as well.  Electrolytic’s on these assemblies were replaced with audio grade KA and long life,low impedance PW Nichicons and the 1MFD to high grade WIMA polypropylene film capacitors.  The associated 2SC1313 BJT’s were replaced with modern 1845 TO-92 devices. 

This is also the time we recapped the F2545 Filter/Muting F2542 switching assemblies with 10 and 33MFD Nichicon low impedance PW capacitors and thoroughly clean each switch and phenolic potentiometer.

Drivers F2436
The push-pull driver stage shares a single PCB with symmetric topology.  Like many Sansui’s and on several of the PCB’s mentioned above, the large electrolytic glue is etch and cleaned off the PCB as well as all fusible resistors which were replaced with 1/2W metal film Vishay resistors.

Remaining electrolytics were replaced with high temp (105C) long life Nichicon PW’s and BiPolar VP’s. The input films were replaced with high grade ECW Panasonic polypropylenes.   The differential pair transistors TR01-4 were replaced with 1% matched 1845 TO-92 devices along with the pre-drivers TR05/06 and TR09/12 1220/2690’s BJT devices.

Function indicators were updated and protection with LED per request.  We also perfected a Meter modification, the original meter uses x2 6.3V wheatlamps each which tend to snap at the legs on most 990/9090's.  The original uses a 10 OHM 1/4W fusible resistor as a voltage drop. I replaced the current resistors with a 47 ohm 1/4W (for 300mW total dissipation) with two 3.5Vf 25mA diodes in parallel.

Mock Up

Audio Notizen

1 comment:

  1. Hello, very interesting work of restoration... Congratulations!
    I dare not do the same thing, too complicated.