Today were showcasing two Marantz 2385 Receivers that came in for restorations. One of the two below was integrated with our new proprietary TA7136 chip upgrade in the PE00 stage. (You can read more at the link here and below)
Having now restored now about X7 2385’s, X5 2500’s and two 2600’s I feel very comfortable with these large 23XX series, albeit dramatically different design and construction from the 2325/2330 series. The 2385, like the 2500 and 2600 models features a much large chassis to fit the massive Toroidal transformer and capacitor bank sub-chassis. The only major differences between the 2385 and 2500/2600 is the power supply requirements which also regulate the P900 scope assembly on the two larger models. The other variance in design of course being the driver sections. One unique feature beside the two 2385’s is the slight differences in the multi-voltage EU version which lacks the Dolby features in the US models.
P850 Power Supply
The 2385 Power Supply is robust package, utilizing two bridge rectifiers with a multi-cap type 6800MFD to establish the driver rail source which were restored with 8800/100V CDE (105C) capacitors. The P850 assembly employs a third bridge rectifier via a series of common cathode/anode devices.
All of the electrolytic in the power supply were replaced with a low impedance, high temp (105C) Nichicon PW’s with an increase in operating voltages. The two axial capacitors were ditched (I hate axial capacitors as they exhibit a general higher failure rate than axial capacitors over time) for two radial 1000/470MFD devices. The common cathode/common anode rectification devices were both replaced with a Ultra-Fast Soft Recovery On-Semi common cath/anode TO-220 device for better dissipation and cleaner rail source along with the Q851 diode to a Ultra-Fast, Soft Recovery UF axial Vishay diode. The remaining TO-220 regulator was replaced with a very robust, modern TO-220 TIP device with performance wakefield thermal compound applied. Remaining smalls signal devices were all replaced to TO-92L and TO-126 modern fairchild devices for better thermal dissipation.
**For models employing our new TA7136 to Adaptive Module/Op-Amp product a three resistors must be changed to compensate for the increase in current draw off the -/+13V rails. Replacing R863 to a 68ohm 5W and R862 to a 220ohm 5W resistors and omitting R870 to a jumper is all thats required!
PQ00 Soft Start & PN00 Audio Muting
The 2385 uses a large in-rush limiting soft start relay and additional protective 48V output coupled relay. The massive soft start relay was replaced with a very high quality Potter & Broomfield 10A 48V KUP series DPDT relay along with a new 20W wire-wound 22OHM in-rush resistor (R003)
Their are two versions of the PQ00 assembly depending on regional unit, with the additional 100MFD capacitor in circuit.
On the PQ00 both MV-13 epoxy type diodes were replaced with modern, axial Vishay 4148 type diodes. All of the small signal devices were replaced with low noise, modern Fairchild TO-92 devices and a TO-126 Fairchild for better dissipation. Electrolytic capacitors were all replaced with a low impedance, high temp (105C) Nichicon PW’s with an increase in operating voltages.
The Audio muting features several protection enablers such as DC Deviation, thermal cascade run-off, muting on delay and clipping engagement.
The relay was replaced with a heavy duty, 48V MY4’ Omron Relays for better handling across the coil taps. The W06B type diode was replaced with a Vishay axial Ultra-Fast, Soft Recovery type diode and a new Fairchild, robust TO-126 device. The Electrolytic capacitors were all replaced with a low impedance, high temp (105C) Nichicon PW’s with an increase in operating voltages.
PE00 Tone Stage W/ TA7136 Upgrade Highlight
The Marantz 2385, 2500 and 2600 all use the same PE00 tone amp assembly with only minute changes employed. The design uses two TA7136 monothilic linear pre-amp IC’s as a differential gain, 2nd stage drivers in the circuit per channel for a total of four (X4) TA7136 chips. One of the units below did not receive the TA7136 upgrade and still performs impressively.
Recently, with our BA312 IC upgrade, released a TA7136 version which applies to the 2385,2500 and 2600 models along with almost a dozen Pioneers. This is the only TA7136 adaption on the market than seamlessly integrates a high-end Operation Amplifier (OP-Amp) , other attempts are hodge podge at best not utilizing the circuit as designed which is where our design comes in! We replace all four pairs of TA7136 with our proprietary Adaptive Module designed by me and the Sparko’s Labs full discrete SS3601 OP-Amps. The increase in performance is staggering, creating a much lower linear frequency response, significantly lowered distortion and SN ratio’s.
AFTER (Restored PE00 With TA7136 Upgrade Installed)
You can read more in detail on the upgrade option at the link below!
The only difference between the 2500/2600 PE00 and 2385 PE00 is the use of two 1K dropping resistors for the establish 13-15V rails and the use of an additional 47MFD dc filter capacitor at the rail input, the 2385 lacks one on the +SE rail. For increased filtering of the DC rail supply, both capacitors were now installed into the circuit (foot print easily allows for the additional capacitor) and increase from 47—>100MFD for better filtering using a audio grade Nichicon FG Fine Gold capacitors.
All of the electrolytics in both units PE00 were replaced with a audio grade Nichicon KT with an increase in operating voltages. All of the 1MFD> capacitors were replaced with a high grade WIMA polypropylene film capacitors along with the .22MFD coupling and .1MFD coupling film capacitors.
AFTER (Restored PE00 Without TA7136 Upgrade)
PT00 Filter Stage & PS00 Tape Monitor
The PT00 assembly, like the 2500 and 2600 affixes perpendicular to the PEE00 assembly using pin connectors for -18dB filters and loudness tap off the precision attenuator volume control.
All of the small signal devices here were replaced with a low noise, modern Fairchild TO-92 devices. All of the electrolytic capacitors were replaced with a audio grade Nichicon KT with an increase in operating voltages. The input coupling .22MFD films and all associated 1MFD< films to .022 were all replaced with a high grade WIMA polypropylene film
The electrolytic here were replaced with a 4.7MFD Nichicon KT audio grade capacitors along with two modern, low noise Fairchild TO-92 pnp/npn devices.
P400 Phono RIAA
The 2500/2600 and 2385 phono stage differ quite a bit in the circuit design with eh larger models using a dual complimentary differential stage versus a single differential and voltage stage int he 2385. In contrast though the 2385 is 100X easier to work on than the 2500/2600 which are 90% hardwired versus molex connectors, making repairs and diagnostics very tricky on the larger two.
Both differential gain stage were matched within 1% with low noise, modern Fairchild TO-92 devices, as well as all remaining devices replaced as similar. All of the electrolytic capacitors were replaced with audio grade Nichicon KT with an increase in operating voltages. 330PF ceramic coupling were all replaced with a high grade WIMA polypropylene 330PF film capacitors.
The P700 uses a massive driver section with a single symmetric PCB for the driver design and two coupled TO-3 heatsink mounts. Comprised of a typical differential stage with a complimentary output stage with triple parallel TO-3 output (quad for 25//2600 series output)
The differential gain stage were Beta matched for better DC control as well as the constant current network transistors with low noise, modern Fairchild TO-92 devices. The Pre-driver array were also updating to a audio application KSA/KSC TO-126 low noise devices thermally coupled to heatsinks with wakefield performance compound. Both 2K and 1K adjustment pots were replaced with precision Bourns trimmers. All the MV-13 type epoxy diodes were replaced with axial Vishay general 4148 diodes.
Matched BETA Differential Pair Groups
All of the electrolytic capacitors were replaced with KT and PW audio grade, low impedance Nichicons with an increase in operating voltages. All of the film/mylar capacitors were replaced with a high grade WIMA polypropylene film capacitors from .47/.1MFD and 1MFD films.
BIAS Confirmation @ 25mV
PC00 FM Buffer PB00 FM Noise & P200 IF AM/FM (RF)
As highlighted below one of the 2385’s had a PC00 Buffer PCB that had suffered serious oxidization corrosion and buildup on the PCB causing all sorts of fun short circuits effectively nullifying its operation. All of the electrolytic on board were removed and replaced with Nichicon PW low impedance type with an increase in operating voltages. Input coupling tantalum capacitors .47MFD were replaced with electrolytic Nichicon PW’s.
The PB00 assembly had a 10MFD capacitor replaced with a Nichicon PW as well as the entire P200 assembly updated with Nichicon PW low impedance capacitors and high grade WIMA polypropylene films 1MFD<.