Monday, October 2, 2017

Paul's Sansui 5050 Receiver

Sansui 5050 Receiver



Today were showcasing a customers Sansui 5050 Receiver that came in for a restoration. The 5050 was released from 1976 to 1977 with a modest output rating of 33W @ 0.5%, the 5050 is favored among many Sansui owners for its incredibly warm and lushes sound.



F-2700 & F-2701 Rectification/Protection and Power Supply
The 5050 was released in a few batches utilizing a different power supply topology. This model used the separate PCB designed F-2700 and F-2701 design while the majority use the F-2649 assembly.


The F-2700 PCB is populated with the dual full wave rectification supplies tied to the 6800MFD filtering capacitors and F-2701 PS, mounted perpendicular to the F-2701 via pin headers. I like this separation of noise prone rectification from the main PS, its a solid design.  All of the diodes including the 1A and 3A axial were replaced with Vishay Ultra-Fast, Soft Recovery type for a decreased noise floor, with the decoupling increased to a 100MFD from 47MFD and all electrolytic replaced with a high temp (105C) low impedance Nichicon PW and Bipolar VP with an increase in operating voltages. The MV-13 epoxy diodes were replaced with general axial Vishay 4148 diodes. The remaining TO-92/L devices were replaced with a modern, low noise Fairchild TO-92 and TO-126 for better dissipation.

BEFORE

AFTER


On the F2701 PS, like MANY Sansui’s all the fusible resistors in this supply were removed and replace with 1/2Watt KOA carbon film resistors including the 6.8 and 2.2 (parallel values.)  All of the electrolytic capacitors were replaced with a high temp (105), low impedance Nichicon PW capacitors with an increase in operating voltages. The relay was replaced with a high quality Omron MY4 type.


BEFORE

AFTER


F-2647 Amplifiers
The 5050 mounts the driver assembly, again perpendicular with pin headers to the F-2701 assembly with a separated TO-3 mounted heatsink for the output stage. The amplifier stage is made of a common-emitter PP stage.

The initial differential pair transistors were replaced with matched Fairchild TO-92 devices at 1% and beta mapped, constant current devices were replaced with a ultra-fast ZTK type TO-92 and remaining drivers with a modern low noise Fairchild TO-126 devices.

Beta Mapping

 The adjustment pots were replaced with precision Bourns potentiometers. The fusible resistors again replaced with KOA 1/2W carbon film type. All of the capacitors were replaced with a audio grade Nichicon KT and VP Bipolar type with an increase in operating voltages. The input coupling capacitors were replaced with a high grade WIMA polypropylene film type. 


BEFORE

AFTER


BIAS Confirmation


F-2646 Tone-Amp
The tone amp features a three-way tone control and high-pass filter with  loudness tapped volume pot. The pre-amp is a simple NPN tiered gain stage output.

All of the small signal devices were replaced with a low noise, modern TO-92 Fairchild devices. The .047/.47 coupling.bypass mylar were all replaced with a high grade WIMA polypropylene film capacitors. All of the electrolytic were replaced with a audio grade KT and Fine-Gold Nichicon as well as the decoupling filter cap to a Nichicon PW which was increased to a 330MFD for a better noise floor, all with an increase in operating voltages. 


BEFORE

AFTER


F-2644 RIAA EQ & MIC Amp
The phono stage and Mic Amp circuits share a PCB assembly mounted under the chassis to the sub-chassis side wall oddly enough, far enough away from the PS but very very close to the RF stages…Similar built using a tiered NPN gain stage.

All of the electrolytic capacitors in both stage were replaced with audio grade Nichicon KT and Bipolar BP, the decoupling was replaced with a low impedance PW and increased to 330MFD for a better noise floor, all with an increase in operating voltages.  The output coupling stage capacitors were replaced with a high grade WIMA polypropylene film capacitor. All the small signal devices were replaced with a low noise, modern TO-92 Fairchild devices. 


BEFORE

AFTER


RF Stages
The 5050 has a simple but very solid super-heterodyne RF stage with a complex sensitive IC front end. All of the electrolytic in this stage were replaced with a high temp KZ and low impedance high temp (105C) PW Nichicon capacitors with an increase in operating voltages.



New custom SMD/LED’s installed to save the original plastic house from melting in the future, as is common with Sansui the Fuse lamp mounts had to be reflowed as the original incandescent bake the solder joints.




AUDIO NOTIZEN


Saturday, September 23, 2017

Brad and Jesse's Marantz 2385 Receiver W/ TA7136 Upgrade!

Marantz 2385 Receiver  & TA7136 Upgrade 



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!


BEFORE


AFTER




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)



PQ00
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.


BEFORE

AFTER


PN00
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.


BEFORE


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 
capacitors. 

BEFORE

AFTER





PS00
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.


BEFORE

AFTER



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.



BEFORE

AFTER



P700 Drivers
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. 
BEFORE


AFTER




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. 


BEFORE

(unit #2)



AFTER


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<.


Audio Notizen