A "Short" Story

The amplifier is tested first to determine the amplifierís performance and definitive problems. All components are checked to ensure that the adjacent components, transistors, etc. were not stressed and consequently prone to future failure. All of the electrolytic capacitors, including the large filter capacitors, are replaced (no generics are used). High temp capacitors for critical areas are tested and matched prior to installation. Capacitors used for the restoration are low ESR, low leakage, and long life components. Sprague, Mallory, BC Components, and Panasonic capacitors are used for restoration. (If you want to supply "designer " audio caps for your restoration, thatís fine, however the performance and/or reliability of the amp cannot be guaranteed.)

The relay is carefully cleaned or refurbished if necessary. Any resistors that are out of tolerance are replaced with low noise, carbon-film types. Not as many resistors go out of tolerance on 15s as do on 16s and 16Bs. All out of tolerance resistors are replaced.

The constant-current circuit is checked for the 4 mA required. On occasion, there is an an amp that would benefit from adjusting this constant-current source slightly to decrease low frequency distortion even further. Adjust amp for symmetrical clip (trim output). The bias and offset pots are cleaned. Power output, noise and distortion, and relay function (if applicable) are checked. The heat sinks and all frame members will be cleaned inside and out. RCA input jacks will be replaced if necessary.

All the lamps in the output circuit are replaced with new lamps. These new lamps are pretested, and the lampís characteristics are matched. Some lamps and lamps of different manufacturers are slightly different from the original lamp. A lamp can be considered a constant-current device and a few lamps I found donít ramp up the same way the originals do. This slightly affects instantaneous power. As previously mentioned, my preference is to solder in these lamps. But, that's your prerogative. If not soldered in, the socket will be cleaned to ensure the best connections possible.

Great care is taken so there will be no lifted traces, overheating of board connections, or excessive bending of wires. Careful attention will be paid so as not to scratch, marr, or ding the amp. These are functional amps and collectorís items. They will be treated accordingly.

Work on these amps is time consuming, in order to complete a fine job. For example, just warming up the amp while monitoring the bias takes time. Even though automated test equipment is used, running specs on the amp still takes a considerable amount of time.

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In order to restore your amp at the flat rate fee, all of the transistors must be in good condition. A few defective transistors may be replaced as part of the standard restoration fee. Any repairs that require major transistor replacement will have to be quoted on an individual basis. Individual defective transistors can be replaced while maintaining the original parameters. Optionally, full complements of semiconductors can be replaced which will yield improved specifications and reliability. Transistors are replaced with either the original equipment semiconductors when stocked, or carefully matched substitutes and upgrades. Repair service (without complete restoration) is also available.

Marantz 15
Repair & Restoration Service

Marantz Model Fifteen
Marantz Repair and Restoration Service
Calibration Service
Evaluation Service
All Marantz 14 and Marantz 15 amplifiers need attention due to component degradation.

Marantz 15 can be restored to new specifications or better for a flat rate fee of $280* per stereo amp
*As of January 1, 2012, the flat rate fee no longer applies to services on the above amplifier. Parts costs from suppliers have risen dramatically. Quotes will be provided at the time of inquiry.

(See Conditions for Marantz 15 Restoration below.) Above price includes all parts and labor. Shipping is additional. Repair service (without complete restoration) is also available and will be quoted on an individual basis.

I have designed, redesigned, modified, and repaired amplifiers for over 50 years, and now specialize in Marantz 14, 15, 16, 16M, 16B, 18, and 19. Shown in the pictures are a few of the Marantz 15s (3 versions), 16s, and 16Bs that have been restored and/or modified. Also shown is a 15 and 16, specifically used to test new types of components. These are a few from my collection.

Quality components have been specifically selected for the Marantz 14, 15, 16, 16B, and 16M. After years of conducting comprehensive testing, manufacturers and their types of components that work best with these amplifiers have been chosen. These components meet or exceed the original component specifications of the amplifiers and will not change the characteristics of your amplifier.

Typical total harmonic distortion figures for a Model 15 amplifier that is correctly set up are as follows:
120 VAC line, 8 ohms, 80 kHz bandwidth, .002% to .008% full power, rises to .016% to .02% at 20 kHz full power. This 20 kHz distortion falls dramatically to approximately .008% at a few watts less than full power.

Modifications such as drilling holes or extending leads are not required to install these components. Only the highest quality soldering, desoldering, and reflow equipment is used in an antistatic environment. Specialized fixtures to hold assemblies in place and solder masks are used to replace components. This prevents stress on interconnecting wires and expedites component replacement. All components are time tested, graded, and matched. High temperature, 105ļC capacitors are used in critical areas. These have a life expectancy of over 200,000 hours. All resistors used for restoration are carbon-film, low noise.

Marantz 15 Electrical Repair / Restoration

HP/Agilent, Bruel & Kjaer, Tektronix, GenRad and other equipment traceable to NIST are used for testing, design, and evaluation. Voltage, frequency, current, R, L, C, & Z, noise, THD, IM, H and S-parameters, network, spectral and FFT analysis, RF power, signal-to-noise ratio, noise figure, RFI, EMI, VSWR, SPL, vibration, wow and flutter, stereo separation, free field acoustical measurements, modulation, temperature, dimensional measurements, torque and weight can be accurately measured in house.

Test & Measurement Equipment Used to Conduct Testing, Design, and Evaluation

Marantz 14 and Marantz 15 Reasons for Failure
(Besides Semiconductor Failure)

There are two 6.2V, 3.91A lamps per channel in the output circuit. The lamps can burn out or have poor contact. When this happens, the amp still works, but at a reduced power level. Unfortunately, on the first two designs, the EB junction of the output transistors now completes the output circuit, and the drivers take the load beyond their dissipation. Needless to say the transistors wonít last long under these conditions, and they donít. On the third design, the transistors will not be damaged, but two resistors will burn. These lamps should be soldered in, but will leave that to your discretion.

This amp also uses Sprague type 30D capacitors, which in my opinion, when aged, are very problematic. I have repaired many pieces of equipment from laboratory test equipment to radios and know that most caps are a weak link in electronics; but when aged, Sprague 30Ds are a nightmare. These caps work fine when theyíre new, but after a while can have catastrophic failure. Without warning they dead short. These caps on the driver board and the one behind the transformer should be replaced. There are five type 30D capacitors per channel.

Problems that occur with this amp due to component degradation are: low power output, poor frequency response, insufficient or high bias, hum and noise, high THD and IM, turn-on thumps, and associated problems due to poor relay contacts.

Marantz 15 Work Performed

Conditions for Marantz 15 Restoration

You should remove and keep your faceplate. It's not necessary to restore your amp. Removing the faceplate is optional, but recommended so that it doesn't undergo any possible shipping damage. Needless to say, it is just four ľ-20 bolts. Be careful not to scratch the faceplate when removing these bolts. Time and time again Ö someone takes pliers, crescent wrench, or sockets that scratch, etc. to remove these bolts. Use the appropriate socket and be careful not to let the socket hit the faceplate or use a piece of plastic such as saran wrap over the bolt then push on the socket. Do not overtighten these bolts. They are not that tight to begin with.

The green power indicator cartridge lamps on the faceplate are on sockets. Just pull the faceplate away from the amp and pull the sockets off the lamps. The sockets are on wires. If these green lamps do not work, remove them from the faceplate. They are on spring clips and easily removed. Ship them along with the amp. I will either replace or rebuild your existing lamp, depending on my stock.

Remove and keep your fuse caps and fuses. If improperly packed, on occasion they are cracked off in shipping. It is not necessary to ship them Ö keep them aside. Wrap both power cords in sufficient bubble wrap, paper, etc. so that the plugs do not scratch the amp. Tape a piece of paper or index card type material over the top and bottom caution labels. Do not use masking tape or duct tape. Use the minimum amount of cellophane tape to hold the paper in place. Do not apply the tape to the labels themselves. Packing material often catches the corner of these labels and damages them.

The amp should be packaged in stiff, thick, rubber foam that surrounds the amp and conforms to the inside the box. Amplifiers wrapped in multiple layers of bubble wrap have been known to survive the trip well. Of course, there are other ways to pack the amp. Thick rubber foam is highly recommended. Multiple layers of carpet padding also work well. It is your responsibility to pack the amp properly so it arrives in good shape. Your packaging should be adequate to safely ship both ways. If your packaging is insufficient, there may be an additional charge for packing material.

You pay shipping both ways. Shipping should be insured both ways. I am not responsible for shipping damage. If you are in the Chicagoland area, and want to hand deliver the amp, we can make arrangements to avoid shipping. (Iíd be willing to travel a little bit to save you a few miles.)

Marantz 15 Shipping and Packaging


Update March 9, 2007 Marantz 15 Restoration

Recently, there have been a few Model 15 amplifiers that have come in for restoration with severe degradation of the output transistors. Breakdown voltages measured extremely low and gain fell dramatically. In these cases catastrophic failure is imminent. I suspect there will be more of these cases showing up. For this reason, all Model 15s will now be tested for this condition as part of the restoration process. Unfortunately, transistors have to be removed to test for this condition. This degradation is not always evident from typical bench checks. If this condition is found, and replacement transistors are necessary to restore the amp, the typical cost for replacement is $40 per pair of transistors per channel. Transistors have to be replaced in pairs.
Notes on Marantz
16 & 16B Amps
Notes on Marantz
14 & 15 Amps
Contact: marantzservices@instrumentresources.com
Click here to read A Few Notes on Marantz 14 and Marantz 15 Amplifiers
Click here to read A Few Notes on Marantz 16 and Marantz 16B Amplifiers
Click here to read A "Short" Story
If you have any questions, email: marantzservices@instrumentresources.com
Marantz 15 Service
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