Vintage Hi-Fi Audio Restorations: Marantz Monster 2385 Receiver

Marantz 2385 Receiver

Heres a pretty fairly rare treat we get to showcase. A Marantz 2385 receiver. A monster of a unit, rated factory at 185 watts/CH! The 2385 steps away quite a bit from the earlier 23XX models and is closer related to the 2500 receiver. The 2385 uses such as the 2500 a dual primary massive toroidal transformer in a black housing along with dual section 6800MFD capacitors. Another difference is the separate driver assemblies known on the 2330/2325 but single topography for the 2385/2500. The 2385 also came in a Euro variant with no AC accessory switching or P600 Dolby integration of course. The other major difference is the implementation of a soft start relay on the 2385 vs the 2330/2325.

Opened Chassis

Power Supply P850

The power supply has a real easy access point clipped above the dual full wave rectification and in front of the filter capacitors. The large 1000/470 MFD axial were replaced with Nichicon TVX type. The remaining electrolytic replaced with high temp (105C) long life Panasonic FC capacitors. The Q851 diode which is a standard S1B102 type was replaced with a ultra fast 4005 diode. Both common cathode/common anode TO-220 rectifiers were replaced with modern MUR1620 TO-220 devices. As noted on the PCB some significant heat is generate off the LED 330 voltage dropping resistor, I recommend swapping it as we did with a new one for longer projected life, unlike the other 23XX series, this is a fixed regulated switching supply.

Before

After

PQ00 Soft Start & PN00 Audio Muting

Separate assemblies exists for the relay and soft start mechanisms. A new PB1467-ND Soft Start was inserted and affixed with matching pinouts. A new Omron low now MY-2 was installed, note the 2385 needs a 48V dpdt relay. Electrolytics on PN00/PQ00 were replaced with high temp (105C) long life Panasonic FC capacitors and didoes updated to general 4148 type.

PE00 Tone Control/ Pre amplifier Stage & PT00 Filter Amp PCB’s

Here is where the 2385 becomes tricky, to truly access the rest of the unit properly to inspect joints and clean switching one needs to fully remove the front chassis plate, same goes for access to the RIAA PCB P400.

All the low level electrolytic were replaced with polypropylene WIMA film capacitors along with the .22 and .1 MFD mylar films. higher value capacitors were replaced with audio grade Elna Silmic II capacitors. Similar to the 2325/330 pre stages 1/2 tier gain is driven by older Bi-polar Opamps TA7136P IC.

The filter amp assembly connects to the PE00 pre assembly via pin connectors in a 90 degree configuration. it is very important your connectors are solid and you do not bend any leads. low value mylar were replaced with .1MFD WIMA and .22/MFD polypropylene WIMA films. Elna Silmic II were used for larger 47/3.3 MFD values.

P400 Phono & PS00 Function Switching

P400 was treated as above with high value capacitors replaced with audio grade Elna Silmic II capacitors and low value with WIMA polypropylene film capacitors. Q411 was updated to a 4148 general diode and Q412 to a ultra fast 4005 type.

Again like the PE00/PT00 stage above the P400 and PS00 assemblies connect in a 90 degree vertical fashion to the front chassis. All the electrolytic were replaced with low impedance, high reliability Nichicon PW type. Germanium diodes were left.

P700 Driver Assembly

This is a massive assembly with a heatsink sized to the 2500 and capable of massive heat dissipation. With each TO-3 bank sandwiched vertically. All the rail, filter and input wiring is arranged in a Molex connector for easy removal, pull the SVT mounts and the chassis rails and the entire assembly pulls out of the chassis. This is the time we gut and re-stuff the 6800MFD filter caps, Panasonic THA’s were used here.

This particular unit came in for a rebuild along with driver issues. Some notorious issues on the P700 are known to eminate from the bias array R731/723 tend to burn up along with diodes Q746 and resistor R721/8703 which consist of 24K and 4.7K values. The trick with Q746 is its a 35V diode which is pretty rare these days, 36 V using a 12/24 or any combination in series will work great rating at 500mW.

New precision 2.2K 500mW Bourns bias and offset potentiometers were replaced along with all VD glass pack diodes to 4148 in series, theirs about 12 on this assembly! Also updated were the first order differential transistors to matched Hfe 1845 type along with tiered Q705/706 to KSC1845 NPN type BJT’s. Also updated were 3rd order driver BJT’s with new thermal compound at Q723/725 and compliment Q724/726 to To-220 MJE15033/32 type for a more reliable consistent device (2SD610/2SB630 NPN/PNP BJT’s) All low value capacitors were replaced with 1MFD polypropylene WIMA film capacitors and assorted mylar/film .1/50/250V films. High value capacitors were replaced with high temp (105C) long life capacitors as this stage see significant voltages and heat.

Audio Notizen

Bias beim emitterwiderstanden punkte .68 array fur 25mV

Punkten J719/&29

P200 RF Stages (FM/AM IF)

The RF stages of the 2385 is comprised entirely on the left bank of the chassis, separated from the AF sectionals as it should be. To fully access the P200 PCB you need to remove the left chassis brace and pull the PCB out from the bracket/shielding its nestled in. Removing most of the molex connectors to the P400/PE00 stages will make this easier and give you more room to work as well. All the electrolytics were replaced with my go-to standard for RF which is the low impedance Nichicon PW capacitors, each tantalum capacitor were replaced with PW’s as well. The bi-polar .47 caps were replaced with .47 stacked films.

PC00 FM Buffer & PB00 Noise AMP

Like the above stages, all capacitors were replace with low impedance Nichicon PW type and all tantalums replaced with PW’s as well. Access to PC00 is achieved easier after pulling the P200 assembly out, this is a great time to VERY CAREFULLY clean the tuning capacitor as well.

Hardware

A new X1Y2 safety capacitor and switching were installed along with a new array of SMD type LED’s for the meters und dial assembly. This is also a good time to replace the meter filter caps with low impedance Nichicon PW’s.

Service Manual Errors Notated

P850 PSC

C853 1000uf 25V ***printing on pCB polarity is opposite what should be

PT00 FIlter Amp

CT23/24 47uf 16V CT24 opposite PCB polarity

PQ00 SOft Start

CQ05 33uf 35V(manual says 22uf 35V)

P700 AMP

C709/710 .47uf 50V NOT PRESENT ON EURO

Audio Notizen

Links

4.8 5.12W (37.09dB)