Today were detailing a Sansui 9090DB Restoration. Similar aesthetics to the 9090 and Black 990(E.) The 9090DB differs from the latter with the feature of the Dolby Noise Reduction circuit and a rated 125W rms output compared to 100W. Topographies of the driver, tuner and power supply assemblies exists as while such as the use of complimentary outputs vs a quasi-complimentary stage in the 9090. Manufactured in the late 70’s through 1979 the 9090DB features a dedicated MM phono, triple tone controls and direct output meters with integrated output protection.
Power Supply F2656 & 12KMFD Filters
The power supply mounted int he rear center of the chassis is also the inboard connector point for the Driver assembly, all of the associated output emitter resistors also populate this assembly.
All of the electrolytic were replaced with high temp (105C) Panasonic FC and PW Nichicon capacitors. Nichicon VP were used for the 4.7MFD bipolar capacitors. The common-cathode-anode diodes were replaced with MUR1620 TO-220 type diodes. BP-Transistors 2SD438/2SD3# and 1211 were all replaced with MPS TO-92 transistors along with the 1OHM fusible transistor.
In relation the two 12,000MFD filter capacitors were updated with new high quality Panasonic THA 12KMFD/80V capacitors.
The protection assembly is located in a very odd angle considering the mounting hardware, this installation was obviously down with a reverse tear down in mind! The Omron MY3 type relay was replaced along with the associated .01/1MFD electrolytic/ceramic capacitors to ECQ polypropylene film type. The remaining electrolytic were replaced with Bipolar VP and low impedance PW Nichicons and FC Panasonics. The fusible resistor was replaced with a 1/2 carbon film KOA.
F2544 Tone & F2653 RIAA & F2617
The tone PCB houses the three dual gang tone controls mounted to the front chassis plate. The front end gains take is comprised of a BA312 pre-amplifier IC and Baxandall negative feedback circuit. Larger filter capacitors were replaced with Panasonic FC’s and AF Audio grade Nichicon KA capacitors. Small signal 2SC1313 to 1845 type TO-92. 100PF ceramics were replaced with stacked ECW films.
The Micamp PCB had the .47 electrolytic replaced with a WIMA film capacitors and audio grade Nichicon KA’s and a PW installed.
The MM RIAA stage has several capacitors housed under the shaft mount, with a good pair of angled magell’s you can access these. Electrolytics again like above with Panasonic FC’s and af Nichicon KA capacitors also replacing tantalums with KA’s. Also like the above its comprised of a BA312 IC three stage direct coupled SEPP topography.
The driver topography differs greatly from the 9090, comprised of a complimentary output stage vs quasi on a symmetric single PCB. The electrolytic on the driver stage were replaced with high temp (105C) Panasonic FC and PW Nichicons. The bias and offset potentiometers were replaced with Bourns precision trimmers and all fusible resistors replaced with carbon film 1/2W KOA’s.
NPN differentials were replaced with match 1% TO-92 ZTX transistors. Bias and Pre-driver transistors were replaced with 2690/733 and 1220 TO-92/TO-220 transistors. Driver pairs were updated to MJE15033/32 pairs. All 1588 and VD1212 diodes were replaced with 4148 and 4148 series pairs.
F2549 AM/FM F2619 & F2655 DB Assemblies
The tuner is quite different on the 9090DB, incorporating a 4-gang tuning capacitor and Phase-Loop Lock PLL circuit with matched MOS FET /AM High-IC devices!
The electrolytic and tantalum capacitors were replaced with low impedance Nichicon PW capacitors and tuning gang cleaned.
Associated F2619 Front end power supply had the electrolytic replaced with high temp (105C) FC capacitors along with updated the 2SD313 to the MJE TO-220 transistor.
The Dolby F2655 had minimal interaction with electrolytic and tantalums replaced to low impedance PW capacitors.