Sunday, June 26, 2016

Sansui 2000A Receiver

Sansui 2000A Receiver

Today we have a Sansui 2000A receiver to showcase.  The 2000 and 2000A/2000X are very similar models besides PCB topography, plus or minus pre amp isolation jumpers and BJT populations. Rated at a modest 35W and manufactured in 1969 this is the last of the early 2XXX series receivers. 

Rectification F1197 Ripple Filter F1195 & Aux PCB’s
The rectification/filtering and block assemblies are all located under the chassis on separate assemblies.  The F1197 had all the electrolytic replaced with a high temp (105C) long life Panasonic FR capacitors and the D003/-4 diodes replaced with Ultra-Fast 400# type diodes along with the D007 @ F1195 and remaining electrolytic.   F1220/1254 had a low impedance PW installed and two .47MFD high grade Panasonic ECW polypropylenes. 

 A new Chassis mount PW high temp (105C) was installed and increased to a 22000MFD/100V capacitor was installed in the mounting bracket  on the top of the chassis. Along with the 3X 2200/MFD 75V capacitors updated with Nichicons to 4700MFD capacitors.

AF Tone F1212 & RIAA F1235
The Tone amp is a single PCB with the multi-tone functions shared. One major issue of the 2000X series is the integration of 2SC458 transistors.  This model only had them within the driver stages but I recommend replacing them if on board. In this case due to the operating frequency the common ksc1845 has a low frequency cut off if substituted.  While this assembly is out we clean all the phenolic based rotary potentiometers and plastic switching assemblies and lubricate. 

The electrolytic on this assembly were updated to audio grade Nichicon KA Fine/Gold FG’s. and low impedance PW’s.  the films at c717/702 were updated to high grade polypropylene MKP’s

The following transistor details is applicable to the F1235 if installed, this unit used a 871 type which is more than fine.  As above the electrolytics were replaced with audio grade  Nichicon KA/FG and low impedance PW’s.  The original  .01MFD mylar’s were upgraded to a high grade Panasonic ECW polypropylene film capacitor.

Driver Stage  F1180
The driver stage is comprised of a PP quasi complimentary output design.  As mentioned earlier the F1180 assembly utilizes the 2SC458 at input transistor TR806/801 which is replaced to a 1% matched KSC1845 transistor.  The input/output coupling films were upgraded to a high grade polypropylene film capacitors (MKP) and remaining electrolytic’s replaced with audio grade Nichicon KA/FG and PW low impedance high temp(105C) capacitors.  Due to the footprint and good tracking the offset(clipping) and bias potentiometers where removed, bathed in D5 and lubricated.  Easier bias notations can be measured at each emitter resistor for a bias of 15mV versus the current draw method.  Also note their are two service bulletins published if intrinsic noise is populated in the circuit.

The integrated Protection indicator is tethered to a output device/input sensitivity 2.5A fusible network in the rear of chassis

RF Sections
The remaining RF stages were all repopulated using a high temp (105C) low impedance PW and stacked Panasonic ECQ film capacitors (1>MFD) and the tuning capacitor shaft cleaned and debris’d.

Buffed RCA Inputs

Audio Notizen

Removed BJT-Caps-Diodes

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