Adams Marantz 4270 Quadradial Receiver Restore

Marantz 4270 Quadradial Receiver

Today were featuring a very nice Marantz 4-Channel Receiver known by Marantz as a Quadradial…the exact release period have some discrepancies.

The 4270 uses Marantz’s exclusive Vari-Matrix circuits used to emulate quadraphonic via stereo source and independent reproduction such as is rated to 70W/CH in stereo and 25W via Quad.

Neat features include front and rear tone controls, the variable martial dimension control (SQ/Vari/Discrete/2CH/MONO) including front/rear balance fader controls!

In addition to new Vellum and Dial custom SMD LED's, new Meter Display Vellum and LED's were installed to restore that even Marantz glow!

P800 Regulated 35V+ Power Supply, PN01 Protection & Filter Capacitors

The TO-220 2SD331 regulator transistors on this PCB are mounted to a large heatsink that actually mounts to the chassis (great dissipation factor!) these originals devices suffer heat and a lot of duress over the years. Modern On-Semi MJE TO-220 transistors were installed in placed of, with a more robust, heavy duty rating and new thermal compound and MICA insulators. The remaining NPN devices were all replaced with a TO-92L package modern Fairchild device for better heat handling.

BEFORE

AFTER

The X4 half/wave rectifiers were replaced with a heavy duty Ultra-Fast UF400# type diodes. All of the electrolytic capacitors were replaced with high temp (105C) long life Panasonic FC and Nichicon high temp PW’s with an increase in operating voltages.

The protection assembly on the PN01 pcbs is an absolute PAIN IN THE ASS to get at…a real dumb design here by Marantz..shame on them. The sandwiched the solder pads through several hardware secured mounts/PCB/mounts so each terminal must be removed (at least L/Side) to access the solder pads for the two MY2 relays which were replaced with a low noise MY2-24V Omron relay’s…again ridiculous….

The two 15,000 microfarad filter capacitors were both upgraded to high grade Nippon 18,000MFD filter capacitor for better handling of the sub-sonic levels at higher gain and better filtering. To top her off here we installed all new 8V SMD custom LED’s and new Vellum paper.

P700 Drivers

Due to the Quadradial design the 4270 features two separated driver PCB’s both with two identical drivers per assembly.  The 4270 drivers use a open frame, hand operated bias potentiometers than accumulate years of dust and oxidization, these are in complete contrasts to the style used for the DC Offset, I have commented several times on the heavy duty plastic potentiometers Marantz occasionally used. If these track well lubricated and clean them and re-install because their are far more beefier than any Bourns device..the Bias potentiometers were replaced with precision Bourns trimmers.

BEFORE

AFTER

All of the BJT devices in all four drivers were replaced, new Fairchild, low noise  TO-92 transistors were installed and matched 1%  BETA for the differential stages, Vbias + stages as well. Pre-Drives and Drives were all updated to low noise Fairchild TO-92 and TO-126 devices for better dissipation. MV-13 diodes were replaced with modern 4148 type diodes in series.

The original electrolytic axial capacitors are always of poor quality from the time period, even in todays standards I opt for radials whenever possible. The two large axial were replaced with low impedance high temp (105C) Nichicon PW’s. High grade MKP polypropylenes for the coupling stage installed and high grade WIMA polypropylene films. Electrolytics were replaced with audio grade KT and Fine-Gold FG Nichicons with an increase in operating voltages. TO-3 Hitachi devices were removed, cleaned and new thermal compound/MICA applied.

P400 RIAA EQ (PHONO)

The phono stage in the 4270 is significantly simplified versus the 22XX/23XX series RIAA EQ’s. The gain stage NPN’s were all replaced with low noise modern Fairchild TO-92 devices matched to 1% BETA. The 100MFD electrolytic were replaced with a low impedance long life Nichicon PW and remaining electrolytic with audio grade KT with an increase in operating voltages. The ceramics and 1MFD were all upgraded to WIMA polypropylene film capacitors.

RIAA Curve Response Report

AF STAGES PD01 & PE01 Tone Amp/Buffer Tone CTRL.

The 4270 uses a very odd way to integrated the initial gain stage PCB, mounting the PD01 assembly perpendicular to the tone controls and solder into tongue/grove sections…All these funky ass positions like the relay BS above is due to REAL ESTATE!…too small of a chassis for this quad but Marantz cheaper out on having new chassis’s so these are akin to the 22XX series chassis (uses the same WC-22 case too).

BEFORE

AFTER

The PD01 Tone amp gain stage had all BJT’s NPN PNP replaced with modern low noise Fairchild TO-92’ devices. The 1MFD  were re-oriented to the rear of the PCB and upgraded to high grade WIMA polypropylene film capacitors.  BiPolar were replaced with long life VP and audio grade KT Nichicons installed with an increase in operating voltages.

The PE01 Buffer/tone stage as above had  all BJT’s NPN PNP replaced with modern low noise Fairchild TO-92’ devices..yes all damn 16… :)

BEFORE

AFTER

The original .22MFD films were all replaced with a high grade MKP polypropylene film capacitor. Large 220MFD to a long life low impedance PW and audio grade KT and Fine-Gold Nichcion capacitors with an increase in operating voltages. 1MFd tantalums and ceramics were all upgraded to WIMA polypropylene film capacitors.

RF Stages

The Phase Converter/Mari-Matrix encoder had the electrolytic replaced with  low impedance Nichicon PW capacitors including tantalum capacitor upgrades to PW’s and Panasonic ECQ films.

including the dolby, FM Front/AM Front Ends....

AUDIO NOTIZEN