Here were are showing another Sansui 5000X series Receiver that came in for restoration. The 5000 series was available in different version thru different years with the 5000 (1967), 5000A (1969) and finally the 5000X reportedly in 1971.
The latter version contain the F10401020 Driver assemblies, which are extremely notorious for overheating and destroying output devices, a significant service bulletin was released replacing this design with the F-6013 driver PCB’s which remedied the cascade bias issues of the early version. This particular unit had the 6013 drivers already installed from factory.
F-1137A Ripple Filter
The Sansui 5000X uses a secondary fed regulated supply, the original supply uses a large format TO-66 device that tends to dissipate significant heat as well as a TO-39 device near a wire wound resistor thats susceptible to higher heat with its package materials.
The electrolytic capacitors were replaced with a high temp (105) long life Nichicon PW and Panasonic FC type capacitors with an increase in operating voltages. Original rectifier diodes were replaced with a Ultra-Fast UF400# series axial Fairchild diodes. The TO-39 2SC device was replaced with a modern heavy duty OnSemiTO-126 device for better dissipation and handling. The chassis mounted 1000MFD was also replaced with a high temp (105C) Nichicon computer grade capacitor.
F1042 Diode Stack
The bridge rectification stage with the 2200MFD filter capacitors separates the a pair of secondaries for the B+/- supplies.
One of the MAJOR upgrades performed on this unit was the removal of the old bridge rectifier and installation of a custom built Ultra-Fast Bridge Rectifier using heavy duty UF, Soft Recovery Axial Vishay diodes
The electrolytic capacitor was replaced from a axial to a reliable radial, high temp (105C) Nichicon PW capacitor with an increase in operating voltage. The TO-39 2SC device replaced with a high gain, ultra reliable ZTX TO-92 device. The two coupling .01 films were replaced with a high grade ECW polypropylene 630V film capacitors
Confirming the AC/DC Regulation
The schematic indicates the use of 1500MFD capacitors when 2200MFD are actually used. The X4 2200 capacitors were replaced with high grade Nippon Chem-Con 2200MFD 100V filter capacitors.Great care is taken to use small profile capacitors here as the TO-66 drivers tend to radiate significant heat.
The 1000MFD chassis mounted capacitors was replaced with a high temp (105C) Nichicon 1000MFD capacitor with an increase in operating voltages.
As noted in the introduction above the original 5000 series utilized a series of different drivers where the thermally couple driver stage would cause a bias cascade and exhibit heat issues. Sansui released Service Bulletin CE-037A which included details on the new F-6013 driver design to be installed on effected units, additional power supply changes are required.
On these drivers the electrolytic were all replaced with a low impedance and audio grade Nichicon PW and KT with an increase in operating voltages. The original input and mylar films were all replaced with a high grade WIMA polypropylene film capacitors. The original open frame potentiometers were replaced with precision 500mW Bourns trimmers.
Some of the F-6013 feature a different differential NPN wether a 2SC984 or 2SC1000 device which was replaced with a low noise modern TO-92 Fairchild NPN device. The original TO-39 requires a high gain device, a high grade ZTX type TO-92 NPN device was installed in place.
Bias Confirmation New Bias notations at the emitter resistor (x1) for (.33ohmX26mA=8.3-8.48mV RXI=V)
CLIPPING SYMMETRY Confirmed
The AF stage on the 5000X is frankly nothing short of a mess with many poor connections of free wire hookups and very high gain 2SC NPN devices.
The electrolytic were replaced with a low impedance Nichicon PW and audio grade KT capacitors with an increase in operating voltages. Low microfarad capacitors and mylar film were upgraded to a high grade WIMA polypropylene film capacitor.
As noted on a prior 5000X we did;
The 2SC871 small signal transistor can be a very tricky device to cross reference as this circuit requires significant gain, the high hFE of the original device is typically at least 450hFE. New ZTX high grade NPN TO-92 were used with a higher gain class than the typical 1845 compliment usually utilized.
F1036A RIAA EQ
The RIAA EQ is contain in a shielded enclosure along with the selector path switch and a large 470MFD capacitor which was replaced with a 470MFD Nichicon PW capacitor.
Some of the F1036A used the failure prone 2SC458 and others are populated with a 2SC632 NPN (2SC871) devices. All of the original small signal NPN TO-92’s were replaced with a modern low noise TO-92 Fairchild devices. The electrolytic capacitors were replaced with low impedance PW and audio grade KT capacitors with an increase in operates voltages. Small value capacitors were replaced with a high grade WIMA polypropylene film
RF AM/FM (F-1006-2/ F-1083-5/ F-1219/1120)
This assembly is not properly notated with the service manual, but documented within the schematic view. Like the remaining RF stages the electrolytic were replaced with a low impedance Nichicon PW capacitors with an increase in operating voltages. The 2SC458 failure prone device was replaced with a modern low noise Fairchild TO-92 device. Below is a comparable view of a pre-eminent failing 458 device.