Saturday, July 2, 2016

Sherwood's S-9910 TOTL Receiver

Sherwood S-9910 Receiver 

Today we are showing off a Sherwood S-9910 Receiver we have in for a customer for a rebuild. The S-9910 Receiver was billed as Sherwoods Solid State TOTL model. Boasting a output at 20-20K with 100W .5% THD>.  Several features set the S-9910 apart such as a trifold output setup A,B and C in a multitude of combinations,  heavy duty Power Transformer with extruded heatsink assembly and multiple Phono inputs for MM and MC and handy Pre-Main out connections. Aesthetically the illumination can’t help but to remind me of 22XX series Marantz.

Power Supply/Protection PCB 0046F
The integrated power supply, protection assemblies include integrated independent speaker relays (MY48V which where updated to Low Noise type and circuit overload with a multistage fused protection Pformer.  The power supply electrolytic were updated to high temp (105C) low impedance Nichicon PW’s and high temp (105C) Panasonic FC capacitors.  All 1S2473 type diodes were updated to 4148 type and TO-220 2SD NPN transistors to MJE1503X NPN BJT’s. The large filter electrolytic was replaced with a 2200MFD low impedance high temp (105C) capacitor. 

Featuring an impressive 30,000MFD filter, these capacitors were upgrade to high quality Nippon/Chem-Con 18,000MFD capacitors for an additional 6000 microfarads of filter :)

AF Tone Control/Pre  PCB 9029B, Tape/Push PCB 9028A-PCB7120   and RIAA PCB 0046A 
The S-9910 has an integrated  variable mic control and triple tone controls with defeat features in the AF stages.  All the electrolytic were replaced with a audio grade Nichicon KA electrolytic and Nichicon Fine-Golds.  Input 1MFD electrolytic were upgraded to high grade WIMA polypropylene film capacitors. BiPolars were replaced with Nichicon VP type. 

All small signal  1681/841 NPN/PNP staged transistors were updated to match arrays of 992/1845 NPN/PNP transistors with matching the tone control initial gain stage to 1%. This is the perfect time with the push PCB9028A assembly out to clean the potentiometers and switching. 

The RIAA stage is housed similar to some of the 22XX Marantz with the function selector control.  Initial PNP differentials were matched to 1% KSA992 transistors.  Input .47MFD electrolytic were upgraded to high quality Panasonic ECW polypropylene film capacitors. With larger 47MFD to high temp Panasonic FC and audio grade KA electrolytic within the signal path.  As above in the AF stages the  841 and 2c1708 NPN/PNP pairs were updated to 992/1845 transistors.

Driver Stages  PCB 0046BA/B/AB
Tied into an array of complimentary push-pull output transistors 2SD427’s and 2SB557 TO-3’s. Each driver is coupled via a molex slide connector to the emitter-heatsink assembly. The extruded single TO-3 mount is perpendicular to the chassis mount. 

All of the electrolytics were replaced with high temp (105C) low impedance Nichicon PW and a .47MFD high grade ECW Panasonic Polypropylene.  D602-4 1S2473 diodes updated to 4148 type and precision Bourns bias potentiometers installed.  The 945/733 BJT’s were updated to 2383/733 TO-92 BJT’s.  The differential pair is comprised of a 2SX1583 Dual Jfet.

RF PCB 0035
The top chassis mounted tuning capacitor/RF assembly is housed in a big heavy plate shielding which is good to see.  All of the BiPolars were replaced here with Nichicon VP and polars with low impedance PW’s down to .47MFD.

New LED’s using custom SMD type festoons were installed as well.

Audio Notizen

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