E. Sutliffe's Marantz 2270 Receiver Restoration

Marantz 2270 Stereophonic Receiver

The 2270 is probably one of the most common 22XX series I get in every year, I would estimate a good 12-15 I completed on average here….for good reason. The 2270 is an iconic vintage component and Marantz flag model for years. Many know its warm undertone and presentation as synonymous with Marantz. The concept design employs many cap coupled stages used in various proceeding models such as the 2230 and 2245 series and variants in the 1060. 

P800 Power Supply

The power plant of the 2270 revolves around a classic protection/regulated single assembly and the B-/+ 48V rails. The P800 assembly has a 35Vdc & 13.5Vdc output. The protection monitors excessive DC deviation occurring in the output stage congruently.

The initial 1A rectifiers were all replaced with a ultra-fast, soft recovery type axial Vishay diodes.  All of the electrolytic capacitors were replaced with a low impedance, high temp (105C) Nichicon PW type, with several DC input/output stages increased in value for better noise filtering, with a noted increase in operating voltage as well. The original TO-66 style regulator was replaced with a modern, more robust OnSemi MJ series TO-220 type with new synthetic thermal Wakefield compound applied. The remaining devices were all replaced with TO92L and TO-126 Fairchild devices for better dissipation handling. The adjustment hardware was replaced with a sealed, precision Bourns potentiometer. The original relay was replaced with a modern 24V Omron series. 

BEFORE

AFTER

+35Vdc & 13Vdc Voltage Confirmation

Filter Capacitors

The 9KMFD filter capacitors were both increased in value for better subsonic reserve and filtering with new CDE type computer grade capacitors.

-/+48Vdc Rail Confirmation

P750 Drivers

I’ve highlighted several aspects of the ASO and bias issues abound with the 2270 so I won’t cover them here redundantly but as documented before the original biasing scheme was replaced with a new TO-126 MJE series device thermally coupled to the driver array versus output dissipation.

All of the electrolytics including tantalum were replaced with a low impedance type Nichicon PW with an increase in operating voltage.  Remaining films to precision/high grade MKP/CDE polypropylene films.  New matched differential pairs were installed and thermally coupled together. As well as several remaining devices with modern TO92L Fairchild devices. Offset and Bias adjustment hardware was replaced with a sealed, precision Bourns potentiometers as well. 

BEFORE

AFTER

Differential Pair Matching Confirmation

P700 RIAA (PHONO) & P400 Pre-Amplifier

The 2270 shares an indentical almost front end pre-amp and phono stage as i’ve highlighted many times, that I much prefer. The phono stage is accurate while the coupled pre-amp stage lends that warm Marantz tone.  The P700 is cap coupled input/output stage with a NPN gain stage.

All the input/output films were replaced with high grade MKP WIMA polypropylene film capacitors. Remaining electrolytic were replaced with a audio grade KT/KA Nichicon type with an increase in operating voltage. The DC filtering capacitor was increased in value and replaced with a Nichicon PW, low impedance type capacitor.  The general diodes and varistor were all replaced with modern axial 4148 type diodes and clipping adjustment hardware replaced with sealed, precision Bourns potentiometers. All of the small devices were replaced with a low noise, modern TO92 Fairchild type. 

BEFORE

AFTER

RIAA Curve Response (1710#329)

P400 PRE

As noted above I love the sound and simplified design of the 2270 front-end audio stage and its warm undertone. Like the P700 RIAA stage both are driven by a single-ended 35Vdc rail. 

All of the electrolytics were replaced with a audio grade KT/KA Nichicon type with an increase in operating voltage. The DC filtering capacitor was increased in value and replaced with a Nichicon PW, low impedance type capacitor. 1MFD> capacitors were all replaced with a high grade MKP WIMA polypropylene film capacitors, inputs were replaced with precision CDE polypropylene films. 

BEFORE

AFTER

RF Stages

Shielding was removed and RF assemblies accessed with new Nichicon PW low impedance type capacitors with an increase in operating voltages installed. 

New Vellum with SMD Warm White 8V LEDs installed in both dial/meter assemblies

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T. Crandall's Marantz 2252 Stereophonic Receiver Restoration

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.

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