Marantz 2252 Stereophonic Receiver
The Marantz 2252 was released from 1977 to early 1980, the 2252 featured several unique features like an extra front bezel, simplified PS and single symmetric driver stage. The driver stage excels in this unit with a great degree of stability.
P800 Power Supply
The 2252 regulated power supply employs a full wave bridge rectifier to establish a zener/regulated 35 and 14V SE supplies. Unlike most P800 assemblies, the protection here is associated on the P700 board.
The original silicon common cathode/anode devices were replaced with state of the art MUR series HexFred type rectifiers with a new high grade polypropylene film bypass capacitor, the half wave rectifier was replaced with a ultra-fast, soft recovery axial Vishay diode. The small signal device was replaced with a modern low noise Fairchild TO92L for better dissipation and a more robust, modern TIP device was installed for a regulator with new synthetic wakefield thermal compound. A new adjustment was installed with a precision, sealed Bourns potentiometer.
All of the electrolytic capacitors were replaced with a low impedance Nichicon PW type with an increase in operating voltage, the DC coupling capacitors were increased to 1000MFD for better filtering.
BEFORE
AFTER
35V+ SE Confirmation
AC/DC Stage
Due to dissipation and the perpendicular mount of the P700 array I wanted to go with a small for factor capacitors to open more exposed surface area, a new CDE computer-grade 10,000MFD filter capacitor was installed.
B-/+ Rail Confirmation
PE01 Tone Amp
The PE01 design used in the 2252 is vastly different than most models where as they employ a BA312 front end/dual. This PE01 uses a NPN/PNP emitter follower PP front end and output stage.
All of the electrolytic capacitors were replaced with a audio grade KT/KA Nichicons, the DC coupling capacitor was increased to 470MFD for better filtering, all with an increase in operating voltages. The inputs and >1MFD capacitors were replaced with a high grade WIMA polypropylene film capacitors. All of the small signal devices were replaced with a low noise, modern TO92 Fairchild type.
BEFORE
AFTER
P400 Phono RIAA
The 2252 uses an alternative form factor Phono stage Marantz used with an integrated selector board reference. The P400 uses a simple NPN gain stage and emitter output.
All of the electrolytic capacitors were replaced with a low impedance PW and audio grade KT/KA Nichicons, the DC coupling was increased to 220MFD for better filter, all with an increase in operating voltages. All of the small signal devices were replaced with low noise, modern TO92 Fairchild type.
BEFORE
AFTER
RIAA Curve Response
P700 Driver & Protection Assembly
Like a few various 22XX series models the 2252 employs a single symmetric PCB. Also noted is the protection on this assembly. The P700 uses a common differential and PP output stage.
Both of the differential pairs were beta matched and thermally coupled together for better monitoring. The remaining small signal devices were all replaced with a modern low TO92L type Fairchilds for better dissipation, also updated were the driver pair and coupled with new synthetic thermal compound. Both adjustments were replaced with a seal, precision Bourns potentiometer.
Beta Matched Differentials
All of the electrolytic capacitors were replaced with a low impedance and audio grade KT/KA Nichicons with an increase in operating voltages. All films were replaced with high grade MKP and WIMA polypropylene film capacitors. VD varistors were all replaced with axial general 4148 in series.
BEFORE
AFTER
Bias Confirmation
Hardware
New Vellum paper was installed in both meters and the front dial display. Someone prior had removed the power switch bracket and replaced with a ugly switch type. This was removed and a new 7A DPDT power switch installed with new silver-cap.
AUDIO NOTIZEN
