Technics RS-676US Restoration

See idler tire replacement procedure here.

I picked up a top-of-the-line 1974 Technics tape deck two years ago and it has been an ongoing project to restore the machine to function. Apart from taking a pretty bad smack over the years which damaged the VU meters, its only major issue was that the Rec/Play switch, which is rather difficult to access, had gotten dirty over the years, rendering playback poor with blown out bass frequencies. I shelved the 676 about a year ago when I found out about its super-rare wired remote accessory, available a few times a year for $300-600 on Ebay.

A couple of weeks ago, this RP-9275A came up for auction. Against all odds, I bid $100 and….. won! While it was in the mail, I ordered some Deoxit Gold G5 contact cleaning spray. It was time to fix the 676.

Just four screws removed from the base of the metal hood exposes the electronics, laid out as simply as any car’s engine bay of this era. The transformer features an actual bent metal heat shield (photo upper right) and the tape speed is controlled by inserting a simple flat-blade screwdriver into a control unit (photo upper left.) I do not have an oscilloscope to guage the proper setting, so I used another tape deck to record a sustained note off an mp3 file. I then put this tape, recorded at the correct speed, into the 676, and adjusted the play speed until it matched the tone of the original file played back separately and simultaneously.

In order to remove the face plate, all knobs and switch covers must be removed. Most are unique and keyed, so this is not difficult. One exception is the Rec input volume knobs, which seat within one another (Left and Right channel controls) and are held in place with set screws.

One of the most remarkable features of this vintage tape deck is its centrally located logic board, which controls various solenoids within the unit by lightly depressing buttons for rewind, fast forward, play, pause, and record. The click-clack of the solenoids snapping between their positions can be a very satisfying sound. With the bezel removed, these contacts can be easily reached and cleaned. The VU meters I replaced last year (photo upper right) help ensure that when you record, you are realizing the full potential of your tape.

The wide drive belt and giant flywheel help to bury “wow and flutter,” irregularities in both recording and reproducing of sound. Potential energy afforded by the oversized flywheel keeps the speed consistent and sounding great. The motor on the right is held suspended away from the chassis by four screws and eight rubber grommets in order to minimize vibration. The tape spool motor, nestled between the belt, indicates a build date of November 19, 1974.

The two particular contacts I need to clean are located on the other side of this breadboard. Another board is mounted perpendicular to this one; it must be pulled up and away from the top first.

The build quality of 1970s Technics is evident in the gold band resistors (seen in tan/brown) indicating 5% tolerance. No visible band, seen in non-audio applications, indicates 20% tolerance, and a silver band, seen commonly in lesser brands, indicates 10%. Two plastic switches for “Record” and “Play” are on this board; I sprayed both generously with Deoxit then pushed on them a few times to ensure they were well cleaned.

Do not use Deoxit to clean tape heads. I used 70% alcohol, but 99% is preferred. Simply rub a Q-tip on the playing and recording heads (from left to right above: Q-tip, recording head, playing head.)

While the unit is disassembled, this is a good opportunity to align your fingernail within a damp cloth and clean the detailed surfaces of all knobs and switch covers.

Another hallmark of vintage electronics seen here is the non-polarized two-prong electrical plug with separate ground post.

After testing the 676, I re-installed the front bezel, all knobs and switch covers, and the metal hood.

Now, the moment of truth…. The type of thing Scarface may have had sitting on the carpet next to him in the hot tub…. The wired remote.

After removing the cylinder over the remote control plug-in, I found four jumper wires connecting several of the 12 holes. I was unable to pull these wires out with pliers, but I soon found out that didn’t matter.

It’s somewhat difficult to discern by this photo, but the plastic cylinder in the center of the remote control’s 12 prongs is slightly larger than the receiving hole on the 676, making it impossible to insert. Note the unit’s statement: Its remote can be “only Matsushita model RP-9275” (photo left) while the underside of my remote gives itself away as an “RP-9275A.” (photo right)

This was an extremely disappointing realization because I have no idea what I’m going to do with this remote control now. The search continues for, specfically, an RP-9275.

On the bright side, the 676 is operational, working perfectly, and I’m glad to have it back on the rack.

Special thanks to Dave McDonald of 12VOLTVIDS for assistance.