MARANTZ Model 2250B – restoration project

As we mentioned on many occasions, we are big fans of Marantz receivers from the 1970s. But while these receivers are deservedly famous for being very well built, after 4 decades most of them are plagued with various ailments. How bad it is, depends primarily on the history of a particular unit: whether it was serviced, how intensively it was used, how many years it spent stored in a basement or attic, and finally whether it fell prey to an amateur tinkerer who decided to add his own “improvements”. There are units that only need minor cleaning and adjustment, there are also those that need a serious amount of work.

Marantz Model 2250B from 1976, which a reader sent to us, definitely needed attention. The receiver was luckily not destroyed by improper storage, it was not very dirty inside or outside, and there were no signs of corrosion. But a previous owner decided to add power cables (two, one ended with a male plug, the other female) connected directly to the main switch. The cables exited through the holes in the bottom of the housing. The purpose of this “improvement” remains a mystery to us – the receiver’s power switch worked properly, and this model has factory AC sockets for connecting additional devices. In addition, one of the previous owners apparently had his own idea for describing various functions of the receiver, because he scribbled his own descriptions around one of the switches – interestingly, those descriptions did not have anything to do with the actual function of the switch. The main fuse cap was also broken, which would prevent fuse replacement if it blew. One set of loudspeaker sockets had enlarged, very loose openings and did not catch speaker cables well, probably due to long term use of excessively thick cables.

That’s what we noticed even before plugging the Marantz in. After we switched it on, the list of problems grew quickly. A few dial and function lights were out, including the STEREO bulb. Some potentiometers and switches were noisy and intermittent. Some buttons did not spring back when the function was turned off. Sound was intermittent in one channel, or rather would not appear at all at low and medium volume. When it did appear (at a higher volume), it was usually distorted. For this reason, it was initially difficult to say whether the STEREO light did not work because the bulb died, or the problem was the tuner.

Measurements showed that the quiescent current required a slight adjustment, and DV offset in one channel was very high – 85 mV. This value should be 0-15 mV, 30 mV is still not bad, 85 mV is definitely too much.

We started with getting rid of the strange cables connected to the power switch.

Because everything was working properly (in terms of switching on and off), we did not bother to check what exactly they were supposed to do, as we did not want to risk damaging the receiver. We simply removed them.

Then we adjusted the quiescent current and DC offset. Fortunately, this did not pose any problems, we set everything according to the service manual, although it did require simultaneous accessing the receiver from the top and bottom (adjustment from the top, measurement points at the bottom).

We replaced the bad lamps. Stereo indicator turned out to be only a matter of light bulb, which was confirmed after cleaning. Remember that the STEREO bulb in Marantz is usually powered from the stereo decoder IC. When replacing it, make sure that the new lamp has the same of lower current rating as the original lamp (in the case of 2250B it is a 12V and not more than 40 mA lamp)

We cleaned the relay and problematic pots and switches. After cleaning, the operation of the receiver improved significantly. Most of the time we had correct sound even at the minimum volume (except for the slight and completely normal volume potentiometer imbalance at its extreme), but unfortunately it sometimes still distorted a little and was slightly intermittent in the right channel, especially at low volume. Evidently there still was a bad contact somewhere. The search took quite long and it turned out that there were several problematic points – especially the connections between boards and the PRE OUT/MAIN IN connectors (rear panel). But eventually all were corrected.

Broken fuse holder has been replaced with a non-original one that matched the opening in the housing.

After restoring proper function, it was time for the cosmetics. We were quite worried about scribbling around the switch, but fortunately their author used something washable and with a rather soft tip (that did not scratch the surface).

After a long bath of the front panel in warm water with soap, it was possible to clean it and remove all traces of scribbling, without damaging the original print. We also washed all knobs and switch caps.

Marantz Model 2250B is a middle of the line receiver with 50W per channel. In the case of a 1970s Marantz, “middle of the line” means great sound, a lot of additional functions, solid construction, and the word “middle” refers primarily to the output power. The functions include a standard set of filters (low and high, loudness, MONO switch) and additionally a Dolby FM filter. There are not only bass and treble controls, but also mid control, and an additional TONE switch that changes the frequency of bass and treble controls, and in the OUT position it defeats the tone controls completely (which reduces the distortion introduced by the tone amp). What’s more, there are separate tone controls for each channel, meaning that you can, for example, boost bass in the right channel only. There are 3 line inputs available (AUX, TAPE 1 and TAPE 2, the latter duplicated as DUBBING input/output on the front panel) and a phono (MM) input. You can connect 2 pairs of speakers with impedance of 4 ohms or higher (8 ohms if the 2 pairs are connected at the same time) and headphones to the Marantz. In addition, the receiver allows to separate the preamplifier and power amplifier sections (PRE OUT/MAIN IN jacks). This allows to use the receiver as a preamplifier with a stronger power amp, use only the power amp section of the receiver with an external preamplifier, or connect a sound processor/EQ between the two sections. While we do not recommend this solution (it is definitely better to connect a sound processor/EQ to tape loop), sometimes there are no free inputs and using PRE OUT/MAIN IN is the only way.

When it comes to sound quality, Marantz Model 2250B does not disappoint. It presents a full, balanced, warm sound, with a nice soundstage and good separation. 50W per channel is quite a lot for the 70s (if you don’t count monster receivers – very expensive receivers with outputs of 2x100W or higher, in those days most receivers were 15-30WPC). 50WPC is enough to drive even quite inefficient loudspeakers in a fairly large room. The sound remains full, and the bass is present and well controlled even at low volume.

The receiver was manufactured in two versions, American and European. The American version does not have a mains voltage switch, it is designed to work only with 120V. The European version has the switch and can work with 110, 120, 220 and 240V. Note that a lot of units sold in the U.S. are European versions, so even if the offer is from overseas, it is worth looking at the photo of the rear panel. It if has the coltage switch, you can use it in Europe without a voltage converter.

Due to the short production period (about a year), the Marantz Model 2250B is quite rare and little known. But don’t expect it to be cheaper because of this – as with other Marantz models from this period, you are unfortunately likely to pay the “collector’s” price. Working units cost more than 500 euros. Is it worth it? If you’re looking specifically for a Marantz from that period, definitely yes. For this money (and probably a hundred more that you will have to be put into repairs/maintenance), you get a great-sounding and beautiful receiver. On the other hand, if you don’t have to have a Marantz, it will probably be much cheaper to buy a comparable Kenwood, Rotel or NAD.

Technical information:

Continuous power declared by the manufacturer – 2x50W at 8 ohms, according to user measurements closer to 2x70W
Speaker impedance – 4-8 ohms
Total harmonic distortion (THD) – 0.25%
Intermodulation distortion (IM) – 0.25%
Frequency response – 20 Hz – 20 kHz, +/- 0.2 dB
Damping factor – 55
Input sensitivity: line 180 mV/100k, phono 1.8 mV/47k (overload 100 mV), power amplifier (MAIN IN) 1.5V/30k
Inputs / outputs: Tape 1 (I/O), Tape 2/Dubbing (I/O), Aux, Phono (MM), 2 pairs of speakers, headphones
Signal to noise S/N – line 88 dB, phono 76 dB
Bass control – +/- 12 dB at 50 Hz or +/- 3 dB at 250 Hz
Mid control – +/- 6 dB per 700 Hz
Treble control – +/- 12 dB at 15 kHz or +/- 3 dB at 4 kHz

Power consumption: max. 220W, idle 35W
Dimensions: 440 x 137 x 365 mm
Weight: 15.4 kg

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