Saturday, April 16, 2016

Marantz 2230 Receiver Restoration

Marantz 2230 Receiver 

Today were showcasing another Marantz 2230 Receiver restoration! One of my absolute favorite Marantz receivers with looks to go, the Bleu LED’s we install in these turn out phenomenal. 

"Best in its class. With impressive specifications and Marantz-exclusive features, the Model 2230 offers more value and performance than any other receiver in its class. We've known that for years. But just recently, one of the nation's most respected independent consumer testing organizations verified it. In not one, but two separate categories -- featuresand performance. It delivers 60 Watts continuous power, both channels driven, from 20 Hz to 20 kHz with total harmonic and inter-modulation distortion well under 0.5%. Stepped, three-zone tone controls for BASS, MID, TREBLE. Provisions for tape decks, phones, record changers and 4-channel adaptors. Ultra low-distortion FET, RF and IF circuitry. Massive heat sinks; automatic protection for internal circuitry and associated speakers, plus the famous Marantz gold-anodized front panel. Looking for a moderately priced receiver? The Marantz 2230 out-does them all."

- excerpted from a 1973 Marantz stereo equipment catalog

Power Supply P800
The regulated 30V power supply is a simple design supplying 66V rails for the drivers and 14/35.6V for the auxiliary assemblies.  All of the electrolytic capacitors were replaced with a high temp (105C) long life Panasonic FR/FC capacitor, The original 2SC1213 NPN transistor was replaced with a modern TO-92L KSC2383 BJT along with the 14V /500mW zener at H806. The mounting glue is etched off as well, the noted 30V TP is at J808. The original filter capacitor was upgraded to a low ESR long life 10,000MFD capacitor and both coupling capacitors upgraded to two low ESR, long life 6800MFD capacitors. A new 7A DPDT power switch and Vishay X1Y2 safety capacitor was installed as well.

P400 Pre-Amplifier
I decided to try some very nice Solen polypropylenes on this stage and the phono to replace with original polypropylene films. I think the the MPK Solen is an incredibly film, cost appropriate yet ever bit as good as the EVO Oil’s we’ve tried extensively.   The remaining electrolytic were replaced with audio grade Nichicon KA/ Fine-Gold series. Per our protocol all 1MFD (AF) stage caps were replaced with a high grade WIMA polypropylene film capacitor. The P400 is designed around a small signal BJT complimentary gain driver stage with variable bass/mid/high attenuations. This same topography is seen in MANY of the 22XX series such as the 2245/70.



The phono stage is in the 2230 is one of the best, bar none. With a nominal Av of 40dB its more than enough drive. Their are some major updates this assembly needs though. The notorious 2SC458 transistors are well known to break down under load with pre-emptive failure and potential noise floor issues, these were replaced with 1% matched Hfe 1845 BJT’s. The original tantalums were replaced with a audio grade Nichicon KA capacitor and Fine Gold 100MFD Nichicon. The original films were again replaced with a high grade Solen MPK polypropylene film capacitors. The original VD glass pack diodes were also replaced with tH709 constructed of two 4148 diodes in series and 708/707H single 1N4148 diodes. 

P750 Driver Assembly
I’ve always been a huge fan of the 2230 topography, very simply push-pull design thats tried and true, very stabile and reliable unlike the 2270. Using a single H751 as a gain drivers to the H752 down to the 3rd order devices. It employs a integrated current limiting protection of the output devices through a current deviation circuit.

All the electorlytics above 1MFD were replaced with a audio grade Nichicon KA and Fine Gold, the 1MFD pre-driver coupling capacitor was replaced with a high grade WIMA polypropylene film capacitors along with a 100PF  WIMA polypropylene at the input capacitor C761. The output coupling C760 .1 MFD film was replaced with a high grade MKS PP WIMA film capacitor as well.  Both Bias and clipping potentiometers were replaced with precision tolerance Bourns pots. new thermal compound was applied to the outputs and thermal tracking diode H005 SV-3A. Its very important to update the glass pack at H757 S3016R with a general 4148 diode for reliability. 

I want to take a special focus on the before and after verification reports, the results are tremendous! Lowered total THD+N response, more linear frequency response at the peak sub sonic and ultra high frequencies, about 3 watts gained with an even better intermodulation response (4:1 60hz/7Khz)

BEFORE Restoration

AFTER Restoration

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