Tuesday, December 5, 2017

Richard's Marantz 1180DC Restoration

Marantz 1180DC Integrated Amplifier



Today were showcasing another Marantz 1180DC Integrated Amplifier that came in for a restoration. The 1180DC, manufacturers from 1978 to 1980 was a good quality Marantz DC coupled/AC 90Watt output integrated unit with some favorable features such as defeating options, dubbing and precise logarithmic tone controls. 


P800 PS
The 1180DC regulated power supply has a dual bridge rectification with a 1A in the P800 and separate filter array with a dual rail 45V supply and two 18,000MFD reservoir capacitors. The P800 located is shared with the PE01 tone stage and P400 RIAA circuit on a single assembly mounted inverted in the chassis and with Pin-Connectors.

All of the electrolytic capacitors were replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages. The original 1A filtering capacitors were increased to 1000MFD for better noise/filtering properties. The original cathode/anode rectifiers were replaced with coupled Ultra-Fast, Soft Recovery axial Vishay diodes. The original NPN/PNP TO-220 rectifiers were replaced with modern, robust TO-220 OnSemi devices thermally coupled with performance synthetic Wakefield compound, remaining devices to Fairchild TO-92L for better dissipation. The 7.5Vzener and remaining diodes were replaced with axial Vishay type. 



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New computer-grade CDE Filter capacitors were installed for the -/+50V source rails.



PN00 Protection
The 1180DC has some notorious protection assembly heat issues stemming from the large dropping resistors and current limiters dissipating. Many of the resistors and solder pads had to be replaced/repaired in this stage.

New KOA/Vishay carbon film 1/2W resistors were installed replacing heat exasperated components. A new modern Omron MY4 relay installed as well as a new common cathode high performance  Ultra-Fast, Soft Recovery TO-220 MUR type rectifier. New general 4148 and 7.5V zener axial Vishay diodes installed. All of the electrolytic were replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages. 


BEFORE


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P700 Driver
The 1180DC drivers are laid out on a single symmetric PCB with molex connectors which is convenient. The P700 does have a hosts of VD varistor issues on the foil side of this assembly that need to be addressed.  As mentioned in prior posts the 1180DC uses a unique to Marantz 2SK109 dual Jfet for the initial differential stage so the bias is pre-determined by a constant current source.

All of the films were upgraded to a high-grade WIMA and MKP polypropylene film compliment including input coupling and IC bypass films. The electrolytic were upgrade  to a low impedance PW and audio grade KA/KT Nichicon type with an increase in operating voltages. The offset adjustments were replaced with precision Bourns potentiometers.

IC current devices were matched as well as pre-driver current devices  with modern, low noise TO-92 Fairchild devices and  thermally coupled together with performance synthetic Wakefield compound. Pre-Driver, Drivers and QT devices were all replaced with TO-220 and TO-126 low noise, robust Fairchild/OnSemi devices. 



BEFORE


AFTER

*Matching Q703/706
PH00 Filter and PE01 Tone
The Tone stage in the 1180DC features a three-way logarithmic tone control and simple differential gain stages.  All of the electrolytic capacitors here were replaced with a KA/KT Audio grade Nichicon and low impedance PW Nichicon capacitors with an increase in operating voltages, the decoupling capacitors here were increased from 100MFD to 220MFD for better noise filtering of the rail source. The input .47MFd films were upgrade to a high-grade MKP polypropylene film capacitor. The small signal devices were replaced with  low noise, modern TO-92 Fairchild devices. 


BEFORE


AFTER


**Heavy attention must be paid to the AC/DC coupling switch on the rear of the panel as these open-frame slide switches can easily build up carbon and foreign matter. New Bipolar audio grade Nichicon Muse 10MFD capacitors were installed.


PH00 Filter stage film capacitors were all replaced all replaced with a high-grade MKP polypropylene film capacitors and electrolytic to a audio grade KA/KT Nichicon with an increase in operating voltages.  The small signal devices were replaced with  low noise, modern TO-92 Fairchild devices.


BEFORE


AFTER


P400 RIAA (Phono)
Like the Tone stage, the P400 employees a simple staggered differential gain stage. As above, all of the electrolytic capacitors were replaced with a KA/KT Audio grade Nichicon and low impedance PW Nichicon capacitors with an increase in operating voltages, the decoupling capacitors were increased from 47MFD to 100MFD for better noise filtering of the rail source. New high grade WIMA polypropylene films were also installed at 680Pf. The small signal devices were replaced with  low noise, modern TO-92 Fairchild devices.


BEFORE


AFTER


RIAA Curve Response


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Friday, December 1, 2017

Bill's Marantz 4230 Quadradial Restoration

Marantz 4230 Quadradial Receiver



Here were showcasing a customers Marantz 4230 that came in for a restoration.  The 4230 is a X2 Stereo + Quadradial Receiver released from 1973-1977.  The Quad Marantz are a unique approach to the dimensional listening session. The Marantz 4230 features a Discrete Mode which direct each input to each respective output, or 2/Ch listening. Using the Vari-matrix mode the rear inputs are internally shunted, Left/Right Input drive the front output and the Left/Right output Rear is synthesized and further attenuated via the Dimension Feature. Optionally a SQ Decoder can be utilized which shunts the signal similar to the Vari-Matrix operation but after plug-in decoder processing. 




P800 Power Supply
The 4230 Power supply is relatively unique for the regulated Marantz PS as it utilizes two full wave bridge rectifiers where as they often employ a full wave bridge and full wave pair.  The Full wave bridge has the + output shunted to ground for a single rail supply. 

The Full Wave Bridge was upgraded with Ultra-Fast, Soft Recovery axial Vishay Diodes and a new .01MFD ECW polypropylene Panasonic Film, the 330MFD decoupling film was increased to a 470MFD/63V type low impedance PW, the 1/2 wave for the lamps was also upgraded to a UF, soft recovery diode. New axial 4148 general and 14V zener installed as well. The adjustment was replaced with a Bourns precision potentiometer. The TO-92 small signal devices were both replaced with NPN TO-92L Fairchild devices for better dissipation as well as the regulator 2SD315 to a more modern, robust TO-220 TIP device and new synthetic Wakefield thermal compound.  Electrolytics were replaced with a low impedance, high temp (105C) Nichicon PW with an increase in operating voltages. New high grade WIMA polypropylene bypass were installed as well. 



BEFORE

AFTER


Confirmation 14/35V Source

The Filter cap was increased from the original 4700MFD capacitor to a Cornell 6800MFD computer grade filter capacitor for better transient noise filtering and power reserve. 




P700 Drivers (X4)
The 4230 designed two separate driver assemblies with two mirror driver circuits per assembly, which is switchable via a rear 30WX12W(X4) selector. Each circuit is comprised of a simple differential,  pre-driver/inverter phase and drivers to output coupled stages.

The differential/pre-drivers and H701 were all replaced with TO-92 and TO-92L low noise, modern Fairchild devices. Pre-Driver and Drivers were replaced with TO-126 low noise, modern Fairchild/On devices. General 4148 axial diodes updated and the original robust plastic frame “Clipping” potentiometers removed, debri’d, cleaned and lubricated and re-installed, the bias points were updated with precision Bourns potentiometers.


All of the electrolytic were updated with a low impedance PW and audio grade KA/KT Nichicon with an increase in operating voltages. New high grade MKP polypropylene/pp films were installed. Two service bulletins pertaining to gain and output devices were addressed on this model. 



BEFORE

AFTER


X4 Channel Bias Confirmation 

PE01 Pre-Amp & PD01 Buffer
Feed after the buffer and monitor/Dolby pathways the PE01 is a much different PE01, using a simple gain NPN/PNP stages for the input/output. Both Tone Controls were removed from the PCB's for a deeper clean and better access.



All of the electrolytic capacitors here were replaced with audio grade KT/KA Nichicon capacitors with an increase in operating voltages. The input were replaced with high grade WIMA polypropylene film capacitors. All of the small signal devices were replaced with a low noise, modern TO-92 Fairchild devices. 
BEFORE

AFTER


On the PD01 Buffer Stage All of the electrolytic capacitors here were replaced with audio grade KT/KA Nichicon capacitors with an increase in operating voltages.  All of the small signal devices were replaced with a low noise, modern TO-92 Fairchild devices. 


BEFORE

AFTER



P600 Dolby & PL01 400Hz Tone
The initial Dolby circuit is a selectable Noise/Reduction/Calibration control for the RIAA/Line playback. Inserting itself prior to the PE01/PD input, normal operation should rest in Off Mode. 

All electrolytic here were replaced with low impedance PW Nichicon capacitors with an increase in operating voltages. New .33MFD ECW polypropylene film capacitors were also installed. 


The PL01 Stage is used for calibration of the record input level of dubbing for reference, as above all the electrolytic’s here were replaced with low impedance PW Nichicon capacitors with an increase in operating voltages.


P500 Vari-Matrix
The P500 enables the synthesized option of buffering the front to rear inputs, the P500 uses a pair of monolithic TA7122 integrated-circuits.  All of the electrolytics here were replaced with a low impedance PW Nichicon capacitors with an increase in operating voltages and high grade WIMA polypropylene film capacitors. 


BEFORE

AFTER

P400 RIAA (PHONO)
The 4230 has a very unique phono stage employing two monolithic TA7129 integrated circuits for gain stages and output.

The decoupling C413 capacitor was increased to a 220MFD PW Nichicon for better noise reduction, the electrolytic were replaced with audio grade and low impedance KA/KT /PW capacitors with an increase in operating voltages. IC bypass capacitors were replaced high grade WIMA polypropylene film capacitors. 


BEFORE

AFTER


Hardware

New custom SMD 8V Meter and Dial Display LED’s installed along with new Vellum diffusion paper and two 100MFD meter capacitors to Nichicon PW type.  All the function/Stereo indicators were replaced with a SMD LED type. 




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