Marantz 2600 Stereo Receiver

Some Background

First off, if you're looking for a cosmetically perfect museum piece, I apologize but this isn't it. In fact, when I acquired this receiver in 2010, it was literally in pieces - a failed repair attempt by a shop tech who apparently had no idea what he was getting himself into. Since its acquisition however, this receiver has been carefully and painstakingly restored to quite possibly "better than new" condition. All electrolytic capacitors have been replaced with new; those in the audio path have been replaced with audiophile-grade Elna SilmicII components, and capacitors in power supply circuitry and in other high heat areas have been replaced with Nichicon UPW series 105°C capacitors, renowned for their high-heat tolerance and excellent service-hour ratings. The old dual-section main filter capacitors have been replaced with new custom-built filters having far greater voltage ratings and improved heat tolerance. The original plastic sleeve-bearing Rotron cooling fan, notorious for rattling and becoming increasingly noisy over time, has been replaced with an all-metal, ball-bearing EBM-Papst fan - far quieter, and vastly more durable than the original. The amplifier modules have been completely rebuilt using brand new, low-noise On-Semi devices, affording higher current capability and better match-tolerances than the original devices. The incandescent dial bulbs have all been replaced with warm-white snap-in 100,000 hour LEDs, so in addition to your receiver running cooler, you will never again need to disassemble it just to replace a light bulb. All switches, controls and connectors have been thoroughly cleaned with top-quality Caig products...and the list goes on. Full restoration details are below.

Cosmetics

In addition to significant fading of the lettering near the volume control, there are some other noticeable marks on the faceplate; a nick on the top edge, a scratch through the words "True Power" and other lesser marks here and there. A good screen printing shop can easily re-screen the faded lettering, orRadio Daze, for example, specializes in re-lettering one-of-a-kind faceplates. I've even created a600 dpi stencil artwork file for a print shop to use for re-screening - I just never had the courage to ship to one of these shops and risk the faceplate getting lost in the mail. The new owner, if s/he elects to have the faded lettering properly redone, stands to increase the investment value of this piecesignificantly. Otherwise, from more than a few feet away, these battle scars fade and the overall impact of this amazing piece asserts itself quiteimpressively.

The included WC-124 walnut case is in excellent condition, with just a few minor issues. The veneer strip on the top-facing edge of one of the side pieces has a split in it towards the rear, and there are a few shallow dents and dings here and there, however none serious enough to attract attention. Due to a treatment of Howard's Restor-A-Finish followed up with Feed-N-Wax, the walnut veneer looks like brand new, with a deep, rich lustre. Unless you find an unopened NOS one, you'd be hard-pressed to find a nicer WC-124.

Functional Condition

What this magnificent machine gives up in cosmetic issues, it more than makes up for in performance. The lucky winner of this receiver will be one of the very few to experience the sound quality of a Marantz 2600 as it was intended to sound when it was brand new, with fresh components and in perfect adjustment. The tuner is incredibly sensitive, and the quartz lock works perfectly. All of the pushbutton switches and rotary controls work smoothly and positively, without any intermittency or noise. The scope is wonderfully bright and sharp, exhibiting no trace of any burn-in whatsoever, and all scope functions work perfectly. The new cooling fan is whisper-quiet, to the point that you'll likely forget that it's even running. The amplifier is powerful enough to peel your wallpaper, yet nearly dead-quiet at idle. And the sound quality - well, words don't do it justice. This receiver delivers tremendous power and clarity, yes, but with detail and finesse - it can effortlessly handle the hardest-hitting rock cuts you can throw at it, yet it's equally at home with your most delicate acoustic selections. Few, if any, Marantz 2600's have been restored to this level of perfection. Here's your chance to own one. Don't let it get away!!

Photos

Here's a shot of the included literature. The owner's manual, specification sheet and magazine ad are all original; the service manual and schematics are professional reproductions. Included is a checklist of all the replaced parts with associated Mouser.com part numbers.

Below is a photo of all of the replaced parts, bagged by board and replacement date. This 2600 is good to go for at least another 37 years!

Restoration Notes

Servicing a Marantz 2600 is NOT for the faint-of-heart! It's the most complex stereo receiver Marantz ever built, and therefore one of the most difficult to service. However, to the credit of Marantz engineers, the 2600 was designed to be easily disassembled, as you can see below. (The really fun part is putting it all back together later...) This is the regulated power supply board. Pretty much the "heart" of the receiver, this board circulates the unit's "life blood" in the form of regulated DC currents to every circuit other than the main power amplifiers. This board also runs hotter than any other board in the receiver, and its parts take the most punishment over time.

Here, the regulator board's big switching transistors have been removed. The white material is dried thermal transfer compound, originally designed to help the transistors transfer their considerable heat to the heat sink they're mounted upon. Over time, this compound dries out and loses it's ability to transfer heat, causing the transistors to literally cook - and eventually die. We're just going to replace these transistors with new ones, as they're likely already heat-stressed. Here are the replacement transistors with new mica insulators, all with a nice even coating of fresh thermal compound.

The new switching transistors reinstalled on the regulator board's heat sink. And, here's the completely rebuilt regulator board. The original 85°C electrolytic capacitors ("caps") have all been upgraded to Nichicon 105°C (221°F) high-heat components; all of the smaller transistors have been upgraded to higher-current-capable equivalents, and all of the standard and voltage regulating diodes have been replaced as well. Heart surgery complete!

This is the speaker protection circuit, designed to connect the receiver to your speakers only when certain conditions are met Therefore, ensuring this circuitry is healthy is important. The old protection relay has been replaced with a brand new Omron equivalent to ensure the best possible connection to your speakers. The relay driver transistor has been upgraded, and the electrolytic smoothing capacitor has been replaced as well.

The soft-start/peak indicator board, before and after restoration. Again, all new, high-heat type replacement caps were used here. As you can see, some dusting was in order as well...

On to the preamp/tone control board. The audio path always flows though this circuitry, so we want to take special care here. In order to do a really good job cleaning the volume control, we need to desolder it.

This way, we can get cleaner into sections of the control that just aren't quite reachable while the control is on the board. The restored preamp/tone board. The volume control has been reinstalled, the larger smoothing caps have been replaced with hi-temp Nichicons, and the remaining caps have been replaced with Elna SilmicII audio-grade capacitors, highly regarded by audiophiles worldwide. The three tone controls are thoroughly cleaned and lubricated with Caig FaderLube F5, and the tone mode switch (at right) is cleaned and preserved with Caig Deoxit G5 Gold.

Finally, the underside of the preamp/tone board is inspected, and any suspect solder joints are reflowed using top-quality Kester silver-bearing solder. Lastly, any excess flux (sticky stuff used in the bulk soldering process at the factory to help the solder stick better) is removed. Here's the underside of the unrestored tape/scope switching board. Yuck!

And, the top of the same board. In addition to replacing the few capacitors on this board, we also have several switches to clean. Unfortunately, there's a large jumper board severely limiting access to four of those switches... Of course, the jumper board is temporarily removed so we can do the cleaning job right.

As the factory soldering job on this board was relatively poor, with most joints exhibiting a very thin solder coat and some joints already showing "heat rings", the vast majority of joints were reflowed. Much prettier than the "before" shot, don't you think? During the restoration, all input/output connectors are cleaned using pipe cleaners soaked in Deoxit Gold G5. This maximizes connection quality while simultaneously retarding oxidation of connecting surfaces.

Here's the filter board, before and after restoration. As in the other audio boards, Silmic II's are used in the audio path and hi-temp Nichicons are used for smoothing. The slide switches were sluiced repeatedly with Deoxit Gold cleaner and preservative.

The phono amp/function switching board, before and after. This one is really fun to access, as it requires the entire front chassis panel to be removed. All electrolytics in the audio path have been upgraded to SilmicII's, and the DC smoothing caps were upgraded to high-temp Nichicon PW's. Incidentally, all replacement capacitors on this and all the other boards were upgraded to the next DC working voltage range. For example, all original 16V caps were replaced with 25V components; all original 25V caps were bumped up to 35V replacements, etc. This costs a bit more, but is well worth the investment to ensure all replacements are comfortably within their tolerances.

Before and after shots of the FM buffer amp board. Not one single original electrolytic capacitor remains in this 2600. Electrolytic capacitors have a finite life expectancy due to their use of electrolyte, a liquid compound within the device that can dry out over time. Any electrolytic capacitor over 20 years old is living on borrowed time, and a quality restoration involves replacing them all.

This is the speaker switcher board, whose opposite side contains the large dropping resistors used to bring the amp's output down to a sufficiently low level to safely drive headphones. Apparently, the previous user must have connected speakers to the headphone jack, which is the only explanation for generating the amount of current flow needed to heat stress the board to this point. Fortunately, a replacement board became available and was installed. A much more satisfactory solution than trying to repair the old board, which looked as though it was ready to crumble.

And here we have the main tuner board - also a chore to access, as the entire left side of the receiver must be disassembled in order to freely access both sides of it. Many techs eschew replacement of tuner board components, citing fears that FM alignment could be adversely affected. However, in my repeated experience, replacing the tired old electrolytics with fresh new components invariably improves performance, as the circuitry is normally returned to its originally intended state. Here then, is a shot of the restored tuner board. ALL old electrolytic capacitors have been replaced with new Nichicons, and any old electrolytics at or below 1µF in value were replaced with Panasonic or WIMA polyester film caps. Film caps are better than electrolytics in that, since they don't use electrolyte, they never dry out and therefore can theoretically last for centuries. By the way, all tantalum capacitors (small blue teardrop-shaped devices) in this receiver were replaced with more reliable film caps as well.

These small shrink-wrapped devices on the scope amp board are junction gate field-effect transistors (JFETS), used for controlling the horizontal and vertical deflection of the 2600's oscilloscope display. Usually, over time, these JFETs weaken and start to cause problems down the line. These have been replaced with fresh new ones as a preventative measure. Here, we have one of the 2600's two power amplifiers, completely disassembled in preparation for a full rebuild. Brand new On-Semi (Motorola) transistors were selected as replacements, as they are superior to the original Marantz devices in their ability to withstand high current, and due to modern manufacturing improvements, they are also better matched to each other. Since the circuit topology remains unchanged, that signature "Marantz sound" also remains unchanged, but amplifier stability and durability is significantly improved. I have no doubt that these are the transistors Marantz engineers would have used had they been available when this receiver was built!

Here are both amp modules, with new transistors installed, showing Marantz's innovative "pin-fin" heat sink design. These "pins" very effectively shed heat from the transistors to which they're attached, which is in turn carried out of the receiver by the rear-mounted cooling fan. This eliminates the need for the big, bulky cast aluminum heat sinks used by Marantz's competitors at the time. The underside of one of the amplifier modules. All connecting pins were carefully cleaned and silver-bearing solder was used in all connections. The thermostatic devices (at left) on both modules were tested to ensure their proper operation.

Here, we're testing the amplifier modules before putting everything back together. And here's the completed power amplifier assembly, rebuilt, tested, and ready for reinstallation into the receiver. This is the most powerful amplifier Marantz ever engineered in any of their equipment - and that includes their professional gear.

This is a photo of the original fan and soft-start resistors.These are rated for 10-Watts, and are barely big enough for the job, as they run HOT! Quite often in 2500's and 2600's, these resistors become brittle over time due to heat stress and it's not uncommon for them to crack and fail. We've eliminated a potential failure point by replacing these 10-Watt ceramic/sand resistors with far superior 25-Watt vitreous enamel resistors. Due to their open design, they shed heat far more efficiently, and have plenty of power handling capacity to spare. An NOS soft-start relay has been installed to further ensure trouble-free circuit operation here.

I had to throw this shot in. Remember I mentioned that working on the Marantz 2600 is "not for the faint-of-heart"? Now that all the old components have been replaced, it's time to start putting her back together... It's very important to take care in reassembly, as many of the plugs are not only interchangeable, they're reversible too! Before we connect each plug, a little Deoxit Gold is spritzed into each hole to maximize conductivity and minimize oxidation.

As each of the original dual-section main filter capacitors had severe leakage in one section (down to about half original capacitance), we need to replace them. Since replacements are no longer available, we'll need to get creative. Here, we're custom-building replacement filters using arrays of smaller capacitors to give us equivalent capacitance, but far greater working voltage and heat tolerance. Details These capacitor arrays fit neatly into hollowed-out cans of exactly the same diameter as the original Marantz dual-section filters. Where the old capacitors were rated at 7,200µF per section at 105 working DC volts and 85°C, these new filters will provide 7,200µF per section at 160 working volts and 105°C.

Here are the completed custom replacement filters at left, shown next to the old Marantz filters. And, the new filters, installed.


All tuning string pulleys are carefully lubricated with high-quality synthetic lubricant. This minimizes friction and gives a nice silky-smooth feel during tuning. Speaking of tuning, here's the 2600's incredible variable tuning capacitor - 5 gangs for FM, and 3 gangs for AM. Receiver tuning caps just don't get any better than this - one of the reasons for the 2600's best-in-class FM sensitivity specs. However, after 35+ years, some maintenance is required. The tuning bearings and shaft contact sleeves are cleaned and deoxidized in order to minimize contact resistance to ground. This ensures maximum sensitivity, minimizes bearing friction and eliminates tuning noise.

In addition to all the other work, a full FM alignment was performed. The local oscillator was adjusted to ensure tuning dial accuracy, tuning cap trimmers and front-end coils were peaked for optimal reception and discriminator coil slugs were adjusted for proper center-tuning and minimal distortion. In the US-version 2600, the Dolby adaptor receptacle must be removed to access the front-end alignment points... This is a dual sweep pattern generated by a Sound Technology ST-1000A alignment generator after the completed procedure. Excellent alignment and minimal distortion is characterized by the flatness and parallelism of the center section's top and bottom edges.


This is a shot of the tuning dial illumination array - all incandescent fuse lamps that will eventually burn out. We will be converting these to cool-running, warm white, 100,000 hour LED lamps. Here, the new LEDs have been installed. As these are "warm-white" LEDs, they very closely approximate the look of the original incandescents - most people can't tell the difference. However, since there are no circuit modifications and the new bulbs just snap in, converting back to legacy incandescent illumination is...well... a "snap"!

Now it's on to the remaining incandescent bulbs. This is the bulb that illuminates the oscilloscope graticule. Since it runs on 8 Volts AC, we'll need to add a rectifier as well as a current limiting resistor to the new LED being installed. This is the replacement graticule LED. It's a "warm white" variety, to more closely match the original bulb. The LED, originally clear, has been sanded to provide a softer, more dispersed light. The limiting resistor and the rectifier are both enclosed in the shrink wrap below the LED.

This is the converted stereo beacon, which uses a unique 360° white LED for more even illumination than the standard 5mm LED... ...and this is the converted "DLB-1" indicator, which illuminates upon insertion of the optional DLB-1 Dolby FM decoder module.


Finally, the tuning needle bulb is converted to LED. A tiny SMD device is used here, and set into the tuning needle with a drop of glue. The completed LED conversion. As these LEDs have a life expectancy approaching 100,000 hours, the owner of this 2600 can pretty much bank on never again having to replace any of these devices as long as s/he owns this unit. That goes for the owner's kids and grandkids, too!

Time for some adjustments. Below, we're dialing in the regulated power supply to deliver exactly 32.0 VDC to the rest of the receiver, as specified in the service manual. Here, we're attempting to "zero-out" all DC voltage from the output signal at the speaker terminals. Generally any value within 20-30 millivolts of zero is acceptable. As you can see, this particular receiver can be adjusted to within a few tenths of a millivolt of zero.

Setting the amplifier's idle current.This is an important adjustment, and should be done once the receiver has had a chance to warm up - after 30-60 minutes or so. Idle, or "bias" current determines how much juice should be flowing through the output transistors to keep them from completely shutting off - which causes "switching" distortion. Too little current introduces switching distortion; too much current can cause the outputs to overheat and become damaged. Marantz says the ideal idle current setting for this receiver is 25 millivolts. As you can see below, the amplifier in this 2600 is particularly stable, and can be adjusted dead-on. Okay, now that we've lavished all of this well-deserved TLC on this magnificent beast, let's see what she's got under the hood. Below is the power test setup - we'll be injecting a 1Khz sine wave into the Aux input and measuring voltage developed across a standard 8-Ohm load. Due to the sheer power of this receiver, very large load resistors are required - you can see these large green devices behind the meters. A set of 500-Watt load resistors is connected to the "Spkr-1" terminals, and a second set of 300-Watt resistors is connected to "Spkr-2". First we'll test into 8-Ohms ("Spkr-1"), and then into 4-Ohms ("Spkr-1" and "Spkr-2" together).

Testing the 2600's power output, with both channels driven into just one set of 8-Ohm load resistors. Normally, once an amplifier reaches a certain threshold, the waveforms "clip" - and you see the tops and bottoms start to flatten out. This is not the case with the 2600. Rather than hard-clipping, the sine wave starts to exhibit asymmetry more common to a tube amp - you can just barely notice it on the oscilloscope trace. You can see 55.57 VAC at this point on the left true RMS voltmeter - left channel power output = E2/R = 3088.0 ÷ 8 = 386.0 Watts. Right channel measured 383.5 Watts. That's right, over 380 Watts per channel. And we're not even really clipping! But wait... Earlier in the description, I mentioned that there aren't too many receivers designed to handle a 4-Ohm load impedance (you subject a receiver to a 4-Ohm load whenever you hook up two sets of 8-Ohm speakers and run all four at once). Unlike most of their competitors, Marantz actually provided specifications for the 2600 into a 4-Ohm load, so they obviously felt confident that this receiver could handle it. For each channel, two 8-Ohm load resistors are connected in parallel to yield 4-Ohm loads, and the same 1kHz tone is amplified until the waveform on the oscilloscope just begins to display asymmetry. Checking the left channel, P = E2/R = (48.48 x 48.48) ÷ 4 = 587.6 Watts. Right channel comes in at 594.1 Watts. I couldn't believe it either, so I double-checked and triple-checked all my hook-ups and then ran the test again. These numbers are correct. I think it's safe to say that the Marantz 2600 is the undisputed KING of "monster receivers", and it's awe-inspiring to see (and hear) what a truly healthy Marantz 2600 can do!

Restoration Services:

I have been working on Marantz receivers for well over 35 years, and have given this one a complete service update, including the following:

• ALL original electrolytic and tantalum capacitors on all boards (including tuner circuitry) replaced with top-quality components:
  • All electrolytic capacitors in the signal path upgraded to Elna "Silmic II" audio-grade capacitors
  • Power supply and most other small electrolytics replaced with Nichicon "PW" series hi-temp (105°C) capacitors
  • All electrolytics 1µF or smaller replaced with Panasonic or WIMA polyester film capacitors
  • Dual-stage 7200µF 85°C 105V main filter capacitors replaced with brand new custom-built dual-stage Panasonic 7200µF 105°C 160V filters
• ALL original incandescent bulbs replaced with cool-running lifetime LEDs:
  • All dial lamps replaced with triple-element, non-flickering snap-in type LED illumination
  • Sub-miniature indicator lamps and scope graticule lamp replaced with 360° LED devices
  • Illuminated tuning needle bulb replaced with LED
  • All LEDs easily reversible to stock incandescent if desired - no permanent circuit changes made
• Regulated power supply board completely rebuilt:
  • All electrolytic caps replaced with high-heat-tolerant Nichicon PW series
  • All transistors upgraded to higher-current-capable Fairchild devices
  • New mica insulators installed with fresh thermal compound
  • Voltage-regulating (Zener) and standard diodes replaced with new
  • Foil side solder connections inspected and reflowed where necessary
• Output and final stage driver transistors upgraded to higher-current, better-matched modern Fairchild devices
• Both main power supply bridge rectifiers replaced with new equivalent devices
• Original sleeve-bearing plastic cooling fan replaced with superior ball-bearing, all-metal EBM Papst cooling fan
• Old disintegrating cooling tunnel gasket replaced with new foam gasket, for more efficient air flow
• Power cord upgraded to grounded 3-conductor computer-grade replacement
• Heat-damaged speaker switching board replaced
• Speaker relay replaced with brand new Omron equivalent
• Soft start relay replaced with NOS Fujitsu equivalent
• Original 10-Watt soft-start and fan resistors upgraded to 25-Watt vitreous enamel type for improved heat tolerance
• Scope deflection transistors (JFETs) replaced with new; scope aligned per service manual
• All rotary and push-button switches cleaned twice with DeOxit G5 Gold
• All potentiometers flushed twice with Deoxit FaderLube F5
• All connectors treated with Deoxit G5 Gold to ensure low resistance, oxidation-resistant connections
• Tuning capacitor bearings and contact sleeves cleaned and lubricated
• Tuning dial cord re-tensioned to ensure slip-free operation
• Cleaned and re-lubed flywheel bearing and all dial cord pulleys with 100% synthetic oil
• Chassis metal cleaned and protectant applied
• ALL circuit boards carefully cleaned, inspected and any suspect solder connections reflowed
• High-quality Kester silver-bearing solder used in all part replacements and re-solder work
• Full FM alignment performed (front-end, local oscillator, discriminator)
• Power test performed to confirm rated output under load
• DC offset zeroed and idle current set to factory specs (after one-hour warm-up/stabilization period)
• All RCA-style inputs, dubbing jacks and headphone jack internally and externally cleaned and deoxidized

What You Get:

• Marantz 2600 receiver, US version, serial number U010125
• Marantz WC-124 3-piece walnut case w/ mounting hardware
• Original 2600 Handbook of Instructions
• Professional reproduction 2600 schematic diagrams
• Professional reproduction 2600 Service Manual (from stereomanuals.com)
• Original 2-page magazine ad for the 2600
• Restoration worksheet listing all replaced parts

Features:

• 300 watt per channel all-discrete, high-current-capable amplifier circuitry
• Independent power supplies for each channel
• Unique heat-dissipation tunnel design with two speed cooling fan for extremely efficient ventilation
• Gyro-touch tuning with signal strength/multipath and center-tuned oscilloscope display
• Capacitive touch quartz lock tuning
• Audio analysis oscilloscope display with front panel centering and amplitude adjustments, and rear panel brightness and focus adjustments
• 300 and 75 ohm FM antenna inputs, FM muting switch, variable muting threshold (rear panel)
• MPX Noise Filter switch - reduces multiplex noise by blending left and right channels
• 2 tape loops, with dubbing from 2 to 1 and 1 to 2
• Front panel dubbing jacks for Tape 2 (Tape 2 RCA jacks also in rear)
• 2 magnetic phono inputs, 1 auxiliary input
• Loudness switch; high (9 kHz) and low (15 Hz) filter switches
• Independent Bass, Mid, and Treble controls for each channel
• Stereo/Reverse/L+R/L/R Mode switch for complete front-panel speaker control
• Main In and Pre Out jacks for using this unit as either a preamp or a power amp
• Tone Mode switch allows treble turnover adjustment to 10 KHz and bass turnover to 10 Hz
• Two sets of speakers may be connected, both sets may be operated together or independently
• Two rear panel accessory outlets (one switched, one unswitched)

Specifications:

Power / Frequency Response:
Continuous Average Power: 300 Watts /ch. @ less than 0.03% THD into 8 ohms
400 Watts /ch. @ less than 0.05% THD into 4 ohms
Power Band: 20Hz to 20,000 Hz
Frequency Response (±1.0 dB): 10Hz to 60,000Hz
Damping Factor (at 20 Hz): 60

Tuner:
Usable FM Sensitivity: 8.75 dBf at 1.5 microvolt
Hum and Noise at 65dBf (1000µV): -80 dB
Stereo Separation: 50 dB at 1000 Hz

Dimensions (h" x w" x d"): 7 x 19-1/4 x 17-1/4
Weight (lbs.): 60.3 lbs.

Additional 2600 specifications are available on Ben Blish's awesome [link removed by ] Web site.

Terms:

If you are not 100% satisfied with this unit, you may return it within 14 days of receipt for a full refund of your purchase price and original outbound shipping (yes, return shipping would be your responsibility). Full refund would of course be contingent upon receiving the same-serialed unit in the same condition in which it was sent, without any missing or exchanged parts. No other warranties are expressed or implied.

Due to guidelines, I accept only PayPal payment. Buyer pays fixed FedEx Ground shipping rate of $95.00, which includes bulletproof packing and shipping insurance, for any destination in the continental US. The receiver and the wood case will be shipped in separate cartons to maximize their protection. Buyer MUST respond within 4 days of the sale end or a non-paying buyer case will be opened in 's Resolution Center. Payment MUST be received within 10 days of the end of the sale or the transaction will be canceled and the item relisted.

I would ask that if you have less than 5 response transactions or have any negative response within the last six months, please contact me for permission to offer - otherwise your offers may be canceled without notice.

Thank you for reading, and good luck to you!

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