Toshiba PC-G10 Cassette Deck Repair

The Toshiba PC-G10 cassette deck was sold in 1983 as part of a Toshiba ‘Rack system’. The system comprised the SB-M20 amplifier, ST-U20L tuner, RS-B20 semi-automatic turntable and one of several choices of speakers, plus a cabinet. There’s very little info online about these systems as a whole, though their components individually are often available on the used market so they obviously sold well.

Sadly most of the complete systems have been separated so it’s rare to find a full setup. As vintage hi-fi goes they sound very nice indeed and are well made components too, as you’ll see herein. I’m told that the speakers were manufactured in the country of sale – for example speakers supplied in the UK with the M20 system were made by Goodmans. It makes sense, as speakers are essentially boxes of air so manufacturing them locally would save on shipping cost especially when you’re shifting a lot of units. The electronics were all Japanese-made.

This deck was suffering from degraded belts. This issue is common in some equipment from the 1970s and early 1980s, particularly equipment of Philips, Sanyo and Toshiba origin. The rubber degrades and turns into a black tar-like substance which sticks to anything, including mechanical parts, motor and flywheel pulleys, and yourself. Few substances will shift it, though acetone (careful not to get it on surrounding plastics), 99.9% isopropyl alcohol and WD40 will break it down.

It is essential that all of this residue be removed as not only will it negatively affect performance, but it will cause new belts to degrade. Fortunately this mechanism is easy to service, and besides the three belts is entirely gear-driven so there are no rubber tyres to worry about. Besides the pinchroller of course, but those don’t seem to degrade and respond well to being submerged in hot, soapy water for an hour or so. You can also use products like Platenclene, designed for rejuvenating printer rollers, to restore their grip.

Five screws let us inside.

This is a simple cassette deck and the electronics are therefore sparse, though there are plenty of calibration pots and test points. Its simplicity means it is also one of the most reliable cassette decks you’ll find. It’s rare for the electronics to fail in these.

To remove the cassette mechanism you have to remove the front panel, which comes off in 2 parts. First the aluminium trim is removed via 4 screws on the bottom and 1 screw on the top. You pull forwards from the bottom to disengage the top clips and the trim can be removed.

There are 2 further screws underneath which hold the front panel. I also removed the recording level knob and potentiometer as I wanted to clean it, and it’s easier to get it out of the way.

The mechanism is connected to the mainboard by two plugs. With those removed, the front can be flipped over to get at the screws holding the mechanism. Open the door in order to lift the mechanism free from the front.

Three screws secure the motor bracket in place. This mechanism is a soft-touch mechanism meaning that the buttons engage the motor, which in turn causes the main flywheel to rotate gears to drive the rest of the mechanism. It’s a simple and reliable system that operates smoothly and quietly, but crucially doesn’t keep the capstan motor running when the deck is powered on like many cassette decks of this period do. This leads to premature wear if the deck is left running in the cabinet like so many were, the earlier PC-G2T being one example. If I were looking for a Toshiba cassette deck, I’d take this PC-G10 over the PC-G2T for that reason alone.

Speed stability is great however, aided by a nice heavy flywheel.

With the motor plate removed I cleaned the residue from the pulleys. A dab of isopropyl softened the glue securing the motor pulley to the motor shaft and allowed me to pry it off with a flat screwdriver. It can then be cleaned without the risk of dripping cleaning chemicals into the motor itself. A dab of epoxy secures it in place during reassembly.

While I was here I dropped a couple of drops of synthetic motor oil into the top bearing of the motor. As it runs quietly I didn’t disassemble the motor to lubricate the bottom bearing like I did in a recent Philips micro system repair.

This mechanism uses three belts. A 45 mm x 1.5 mm square belt drives the reels from the outermost section of the motor pulley. A 74 x 4 mm flat belt drives the capstan flywheel from the innermost section of the motor pulley. And a 60 x 1.2 mm square belt drives the tape counter from the supply reel.

You can purchase all of the required belts from DeckTech, who produce excellent belts to a high specification. I’ve used DeckTech belts in most of my recent cassette deck restorations and in all cases the serviced machines meet or exceed the manufacturer’s specifications for wow and flutter. The speed control is at the rear of the motor and was set using 1kHz and 3kHz calibration tapes.

These mechanisms were one of the quietest available when brand new, but as they age the plastic gears driving the take-up and supply reels harden slightly. Because of this they tend to make a slight grinding sound on playback. You can combat this by applying a pTFE grease or silicone grease to the gears.

The gears don’t tend to crack or deform and this isn’t a major concern. I suppose new gears could be 3D printed in a softer plastic, but packing the gears with grease is recommended anyway and it tends to solve the problem.

I checked over the electronics using a Toshiba service manual and found them to still be perfectly calibrated after nearly 45 years. There were no leaking capacitors or out of spec components to be found either. These machines may not have been at the pinnacle of Toshiba’s output but they are still built to an extremely high standard with some of the best components available at the time.

I did however have to tweak the azimuth which presented the only real design flaw of this machine. The tape door doesn’t come off, and though there is a tiny access hole in the gap beneath the door and frame it wasn’t sufficient to give access to the adjustment screws with any tool I had on hand. It’s easier to adjust the azimuth with the front panel removed and full access to the front of the mechanism, but you can get at the screws by removing the aluminium trim as described above which will give better access to the access holes beneath the tape door. Azimuth can be set using an oscilloscope and a 10kHz reference cassette, or you can do it by ear. You’ll need a well-recorded cassette, ideally prerecorded or recorded on a machine that is known to be in perfect alignment. You then sum the output of the tape deck to mono, either with a mono switch on your preamplifier, with a mono summing option in a DAW or a custom output cable. You can then adjust the azimuth screw beside the head to maximise the treble.

With the deck back together I have it a few hours of play to let the belts bed in and re-adjusted the speed accordingly. It’s always a good idea to do this, and is something often overlooked by service techs. The speed won’t change dramatically with a new set of belts, but it’s enough that someone with perfect pitch should notice.

The cassette deck sounds crisp, clean and quiet. It’s not your typical ‘70s era warm and fuzzy sound. In fact it’s very reminiscent of its time – when CD was inbound and high-fidelity was a buzzword taken to mean accuracy and neutrality, not coloured tonality and bullshit marketing as it now seems to be.

You even get a pair of front-mounted microphone inputs for recording as well as the standard rear RCA connections, though thankfully there’s no monitoring facility for impromptu karaoke. These are fine decks and well worth the little they cost to pick up on the second-hand market.