Sunday, March 13, 2016

Marantz 2325 Stereophonic Receiver

Marinate 2325 Receiver

Here we have another Marantz 2325 receiver for a restoration. The 2325 rated at 125W/8OHM is one the most popular receivers we receive here at Hallo-Fi. The 2325 has superb construction, solid chassis with robust RF shielding, 30,000 combined microfarads of filter (36,000 after rebuild), dual symmetric driver modules and an excellent phono stage like most of the 22XX, 23XX series receivers. 

P800 Power Supply
First up is the 35V regulated power supply.  The only issue I have with the 2325 is the placement of the P800 assembly, in other Marantz the PS is located in the front end of the chassis away from the AF sectionals. They least they should have done is add another shielding bracket such as on the left driver board. 


All of the electrolytic capacitors were replaced with high temp (105C), long life Panasonic FR/FC capacitors, its important at this point to strip the PCB and remove the glue used in large vertically mounted capacitors, this glue also covers several resistor arrays, all of which were pulled and replaced along with a 10 Ohm 1/2W to a MOX type. The common-cathode rectifier diodes were replaced with coupled ultra-fast diodes and the original relay was replaced with a low noise Omron LY2 24V type. 


 Both 15,000/80V microfarad filtering capacitors were replaced with a low ripple 18,000/80V Nichicon capacitor. To finalize the AC/PS section we remove the power switch, which in Marantz is notorious for gumming up and arching, replaced with a 7A DPDT 250V push-switch with a new Vishay X1Y2 safety capacitor.

P700 Driver Assemblies
Its always a pleasure to work on the 23XX series Marantz due to their modular designs. The 2330 and 2325 are very similar and drastically different than the 2385/2500 topographies where as the 2330 does have thermal tracking diodes ran back through the P800 assembly.


First off H718/719 VD1122 diodes were updated to 4148 type per SB. Next up all the electrolytics were replaced with high temp (105C) low impedance Nichicon PW capacitors. The original 33MFD tantalum was replaced with a audio grade Nichicon KA and the coupling 1MFD film replaced with a high quality ECW polypropylene film capacitor.  100PF audio path ceramics were replaced with high grade WIMA pp films as well.   The differential pair transistors at H701/702 were replaced with 1% matched KSA992 BJT’s and thermally coupled together. The H703 2SA722 transistor was also replaced with a KSA992 FBU gain BJT due to failure nature of the 7XX series BJT’s. 3rd order driver BJT’s and output device TO-3’s had new MICA and thermal compound applied. Bias beim emitterwiderstand (dual) fur 20mV.


PE01 Pre-Amp/Tone Assembly
Like similar pre-amps (2275,23XX) the 2325 uses a first order IC the BA312 as the initial gain drive for the pre-amps stage.  This typical IC such as with the Sansui 2SK97 DIP IC, has a Single-End 3-NPN BJT configuration.  


All the tantalums at 1MFD> were replaced with high grade WIMA polypropylene film capacitors and 2.2MFD< with audio grade Nichicon KA electrolytic capacitors. All other capacitors were replaced with a low impedance Nichicon PW electrolytic.  C37/C38 Bi-Polar electrolytic were replaced with Nichicon VP bi-polar electrolytic due to their transparent characteristics. Input coupling films at C05/06 were replaced with high quality ECW polypropylene film capacitors.  All the BJT’s 2SA721 & 2SC1327 were replaced with matched 1845/992 NPN/PNP BJT’s, as I’ve noted many noise floor issues revolving around these compliments. Also note the SM schematic indicates an error as it titles both HE05/06 as 2SA721 but ones a NPN/PNP.


P400 RIAA(PHONO) Assembly
The phono stage in the Marantz are universally prized for their sweet presentation. Their are though some significant updates that need to be made to this assembly in most Marantz 22XX,23XX series receivers and integrated. The biggest is the removal and update of the failure and nosey prone 2SC458 NPN transistors. These are replaced with 1% matched KSC1845 transistors. The other are to explore is the use of the glass-pac diode at H409 which is a VD1212, replaced with two 4148 diodes in series. 

The original axial was replaced with a high quality Nichicon TVX axial, the original 1MFD tantalum capacitors were replaced with high grade WIMA PP film capacitors, along with the original 1MFD films at C414/415 to ECW polypropylene film capacitors. Low impedance Nichicon PW’s were installed at C403/404. 


RF Sectionals
Remaining RF sections were cleaned and electrolytics and tantalums replaced with low impedance PW’s.  Also noted at PH01 Buffer assembly under the chassis a VD1222 glass-pack diode was updated to two 4148 diodes in series.  The tuning capacitor was carefully cleaned, lubricated and dusted. 

Audio Notizen
below are impressive final True RMS (W/RMS) output results and Overall Total Harmonic Distortion + Noise (THD+N) for this 2325 Marantz.

Rated Power Output (continuous AVG power per CH/ all channels driven)
Peak 34.5Vrms 147.06W @ 0.114% THD+N

Left (output RMS)
34.5 *Clipping achieved +.50mV gain) 
34.5(1190.25/8) 148.781 Wrms @ 0.114 %dB THD+N

30.76 (946.1776/9) beim 118.2722Watts

Right (output RMS)
34.3 *Clipping achieved +.50mV gain)  
34.3(1176.49/8) 147.061 Wrms @ 0.113 %dB THD+N

34.3(1176.49/8) 147.061 Wrms @ 0.113 %dB THD+N

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