Saturday, July 18, 2009

Lil' Mar: Step #1

Lil' Mar is a petite Marantz 4220 quad receiver from the mid '70s. Or, as the faceplate says: 'Stereo 2 - Quadradial 4'! Orion says it was sold from 1974 to 1978 and retail list price was $329. The more authoritative says it debuted in '73 and listed in '74 for $299. It was the smallest and lowest powered Marantz quad receiver. Orion says it packs 15 watts per side (stereo, I assume), but lists it at 2x20 or 4x8. It is not exactly a powerhouse, even by the standards of the mid '70s, but I imagine it would drive a dorm room 2 channel rig quite nicely. As for quad, I hope they chose their speakers carefully.

Lil' Mar is not a standard sized component. It is only 14" wide; the similarly powered stereo 2215 is 17.25" wide. lists it at 16.875" wide, but that has to include a wood case.

My initial listen was not particularly favorable. One channel was down in volume and noisy. At the very least I wanted a stable amp that would play vinyl well, so recapping the phono, regulator, and output sections was mandatory.

Cramming 4 channel gutti-wuts into such a small space required some engineering trickery. The regulator was relatively easy to access at front right, but the amplifier was going to be a bit complicated. The heat sink occupies the center of the unit with the board on its left. This is not a pop-out like the wonderful Marantz 2275. It's more of an unscrew/tug/unscrew sort of effort so I decide to procrastinate a bit and save it for next time. In the photo below the tuners are at the left, nicely shielded as Marantz is wont to do.

Underneath you can see the preamp/tone control circuitry at the right, behind the faceplate. It's a bit daunting. The board just above the heatsink is the SQ quad circuit board. All the way at the top you can just make out the phono board, facing down.

I removed the two screws on the regulator and recapped it with Panasonic FCs and FMs while it was still tethered to the wires connecting it to the rest of the amp. They were a bit short, so it was a bit awkward soldering. If that engineer had specified just another half inch of wire I would have complimented his foresight at this time. But, no.

The phono section was much of the same: two screws and some tugging. It is mounted to the side of the chassis, under and to the left of the tuners. Marantz phono sections tend to have a significant number of film caps, but not this one. It has 8 electrolytics, 4 films and 4 ceramics. If I recall correctly, the 2275 has a single electrolytic cap in the phono section. So I could feel good about myself I replaced the two output coupling caps at the far right with Elna Silmics at 22 mfds instead of 10. The rest were replaced with Panasonic FCs. Here is the phono board 'before'.

All in all, I replaced 12 caps, fired it up and the amp was stable. So step #1 is complete and the next trip to the bench will deal with the amp itself.

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