Technics RS-M225 & RS-M17 Cassette Decks Overview & Belt Replacement

Cassette deck production was in full swing by the end of the ‘70s. Most manufacturers had at least a few models in the lineup, and some had a plethora to choose from. Panasonic sold decks under the ‘national’ branding as well as the Technics brand. Many components were shared between them, and it was really an effort to shift more units than any indicator of a quality difference. If you were on a budget you bought the National Panasonic model, if you wanted the high-end option and the bragging rights that came with it you bought the Technics. Either way you’d get a high-quality tape deck, usually with the clunky piano-key operated mechanism that was common at the time.

But just a couple of years later, things were shifting. Computer control and soft-touch mechanics were all the rage. Devices were slimming down, shedding the pounds and adopting sleek, slimline fascias to stack neatly in rack cabinets. And branding was unified too. Panasonic had shifted production of integrated all-in-one stereo systems to the Panasonic brand, and all but the lowest end hi-fi components were branded as Technics.

Technics M17 Front

The two cassette decks showcased in this article demonstrate that transition perfectly. The 1979 era RS-M17 is undeniably a ‘70s design, with its bulky stature and chunky controls with no servo-assisted mechanics what-so-ever. The 1981 RS-M225 is slimmer, nearly tall enough to accommodate the height of a cassette tape and the transport buttons beneath the door. Thos transport buttons require a gentle push, and are assisted by solenoids and gears to enact the desired functions.

The M225 brought other advances to including support for metal tape which extended the frequency response to 18kHz. Both are two-head decks at the lower end of the Technics range, but until the era of computer control came along you tended to find the same (or a very similar) mechanism used across the board, with electronic upgrades to improve frequency response, drop noise levels and add additional features to differentiate the models. There were three-head models too with real-time monitoring, and the 1980s brought the first direct-drive models too, at least from Technics.

Technics M225 Front

Both decks have Dolby B noise reduction, single electronically controlled DC drive motors, onboard microphone preamps, mechanical counters, record muting and support for the popular audio timers. DBX was offered in the 1981 lineup but only in the high-end models. It was a scarce feature in low-end decks though it did make it to a few. Even fewer twin decks got DBX noise reduction, though the RS-B33W was one of the better ones.

Both of these decks needed replacement belts. Both are fairly similar in their construction. Let’s start with the RS-M225.

Technics M225 Inside Overall

To remove the mechanism you first remove the front fascia. The mechanism comes out from the front, once the cabling behind has been unclipped from the plastic frame. There is a further cable guide attached to the mechanism itself beside the motor. Take note of how the cables are oriented when you remove the mechanism, and try to reassemble with them routed similarly.

Technics M225 Behind Mechanism

That cable guide unclips, though be careful as the plastic becomes brittle with age. You’ll also have to cut various cable ties around the mechanism. You can then remove the rear motor plate to expose the flywheel.

Flywheel Backplate

I took the opportunity to remove the flywheel at this point to clean it thoroughly and re-oil the bearing.

Clean the flywheel, reel drive and motor pulleys with isopropyl alcohol. Be careful not to lose the washer between the flywheel and its bearing. That washer applies pressure to a spring which in turn keeps the plastic drive gear in place. It also raises the height of the flywheel slightly to clear the mechanism.


I lubricated the capstan shaft with a lightweight synthetic oil but any lightweight motor or gearbox oil will be fine. I lubricated the motor with the same, by adding a drop below the pulley. Clean the thrust plate too, and the rear of the flywheel shaft. Lubricate with a light to medium silicone grease.

Mech Belts In Closer

Getting the belts in is a bit of a pig. Make use of the small plastic pegs near the motor to stretch the belt over the flywheel and hold it in place while you assemble the two halves of the mechanism. 

Mech Belts In Further

Then replace the counter belt at the front of the mechanism, by removing the plate covering the reel tables and threading the new belt over the right-most reel, behind the counter and around its pulley. Replace the cable folder and re-route the cables as they were originally, adding nylon zip ties as necessary. Reinstall the mechanism taking care not to trap any of the cables between it and the plastic chassis.

The RS-M17 is a different animal as far as servicing is concerned, though it’s actually similar in its construction.

Technics M17 Overall Inside

You don’t have to take the mechanism out to change the belts providing you have a good set of stubby screwdrivers. However this particular unit was suffering an issue of dry grease causing the buttons to stick, so I did end up removing the mechanism. It comes out through the front again, but some of the wiring is soldered. No matter, if you remove the wire ties and coax the wires from their retaining clips on the chassis frame you can gain enough length to swing the mechanism out of the deck and lay it down front or back to be worked on.

The motor and flywheel are mounted to separate plates. The triangular plate covering the flywheel comes off with three screws. The motor plate is held by a single screw and two metal tabs, which are a tight fit into the mechanism frame. You may need to bend these tabs slightly with a pair of pliers to wiggle the motor free. I didn’t take pictures of this bit, but you’ll see what I mean. There is 1 large belt that goes around the flywheel and the motor to drive the mechanism, which can be replaced at this point.

However if you remove the flywheel, you can gain access to the rubber idlers that drive the reels. There are several of them, and it’s possible to clean them using cotton buds and IPA without removing the second layer of the mechanism.

The second belt drives the counter and is accessed by removing the door if you chose to fit the capstan belt in place. Remove the four small screws to detach the button assembly, pull the transport keys forward and swing the assembly up and out of the way. Then remove the cover over the reel tables which is held in by two small screws. You can then unhook the counter belt, and thread it through the metalwork behind the counter, installing the new belt in the same way. If your belt is snapped or missing, the counter is driven by the right-most reel, and the belt must be set so that it runs behind the counter mount and over the counter pulley.

Technics M17 Right Board

Speed on both is set through the adjustment hole in the back of the motor. I recommend bedding in the belts for a few hours before you set the speed. You adjust the speed using a 3kHz tape, and should be able to achieve a figure within 10Hz providing you used good belts. I used DeckTech belts, and because I lubricated the mechanisms not only did they run in near silence but they also adjusted to within 5Hz of the 3000Hz mark, which is at the limit of the accuracy of the test tape.

Technics M17 Front Turned On

These are fantastic sounding decks from the height of the stereo wars, when even the low end kit coming out of Japan was built and specced to a high standard. Noise levels are low, and the sound is crisp and clean, even if the stereo imagine isn’t as expansive as it could be. The dolby implementations aren’t too aggressive on playback or recording and track very well even with a difficult input signal, such as a highly compressed CD from the loudness war era. These decks make great recordings on all supported tape types, with plenty of headroom in the preamps to maximise the level on the tape without causing audible saturation in the preamp itself.

Technics M225 Turned On

There you have it. Two successive generations of Technics cassette deck, entirely different yet strikingly similar at the same time. Guide prices on the used market for the M17 are £10-20 broken, £20-40 working but unserviced, £55-80 serviced correctly. The M225 £15-30 broken, £40-60 working but unserviced, and up to £110 serviced properly. Prices depend on condition and the presence of original packaging or documentation.

By Ashley

I founded Audio Appraisal a few years ago and continue to regularly update it with fresh content. An avid vinyl collector and coffee addict, I can often be found at a workbench tinkering with a faulty electronic device, tweaking a turntable to extract the last bit of detail from those tiny grooves in the plastic stuff, or relaxing in front of the hi-fi with a good album. A musician, occasional producer and sound engineer, other hobbies include software programming, web development, long walks and occasional DIY. Follow @ashleycox2

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