I’ve been critical of Aiwa’s tape decks recently, and for good reason. My experience working on the AD-WX727 and AD-wX929 twin decks, the latter due to return for a second round, as well as some undocumented Aiwa machines left a bitter taste in my mouth. But they did produce some decent hardware in the same era and this, the AD-F500, is one of the more economical examples.
This is a single deck with a two-motor mechanism, a slightly upgraded version of the AD-F410, AD-F450 and AD-F470. The mechanism is full logic, naturally, driven by a pair of solenoids and gears driven by the primary flywheel. The second motor is dedicated to driving the reels for what Aiwa called a “super stable” transport with “class-leading” levels of wow & flutter. I’m sure Technics could disprove the latter claim with their direct-drive decks of the time, but confined to its budget class the AD-F500 would be at or near the top of the pile.
It’s well put together too, even if changing the belts is a bit of a pain. The flywheel is substantial which gives decent speed stability figures, and the mechanism is quick and quiet – almost inaudible in playback. Winding times are unusually speedy too. Aiwa’s signature Anti-modulation tape stabiliser is fitted to the door to securely clamp the cassette shell in place. AMTS is a curious feature given that logic suggests one would be better off stabilising the tape itself with a closed-loop system, rather than stabilising the shell in which the tape is free to move to a degree. It is found in most Aiwa tape decks of the time though, and most Japanese manufacturers had similar ideas which if nothing else made their tape doors quite substantial.
You get adjustable recording bias, sensitivity, balance and level, with Dolby B, C and HX Pro noise reduction and seven-step, 30dB level meters. This model has a manual tape counter with no counter reset, but you do get audible cuing by holding the winding buttons during playback, and a scanning feature which will identify the silence between tracks.
I was impressed by Aiwa’s implementation of this feature as it works very efficiently, avoiding unnecessary winding and mechanism cycling as it searches. Pressing the fast forward or rewind buttons during playback initiates a scan for either the next track on the tape or the start of the current track. Holding the winding buttons initiates audible cueing, which plays the tape at high speed at a reduced level to locate sections on a track. This was often used in combination with low-frequency recorded tones on a tape, which at winding speeds would be heard as an easily identified ‘beep’. In both scanning modes the heads are lowered slightly to reduce head and tape wear.
This particular example didn’t work on receipt. It had the usual problem of degraded belts. In typical Aiwa fashion they had turned to a sticky tar-like substance, and a lot of clean up was required to get the mechanism back in fighting trim. I didn’t photograph the process, but here is a quick rundown of what is involved. Many of these steps are similar to the mechanism in the AD-WX929. The pictures in that article should give you an idea of what you’re dealing with.
Getting the mechanism out is relatively easy. I did it with the front in place using a small screwdriver, but you can remove the front to make things easier. Careful though – the front PCB is connected to the mainboard by a series of pins which mate to receiving sockets on the rear of the front PCB, and are easily broken if you pull the front at an angle. There are clips to either side, each with a securing screw and two screws underneath. You have to release those clips and pull the front panel straight forward. You can remove the power switch to free the front entirely from the unit.
Four screws remove the mechanism and its lower mounting plate. A further two screws remove the the mounting plate from the bottom of the mechanism. You can get away with leaving the head wires tied to this plate, but it is necessary to remove the plate to access the screw beneath which is one of four screws holding the rear mechanism plate in place. The others are to either side. With those removed, and some gentle prying, the back plate will release. You can then lift out the flywheel, taking care not to lose any height washers that maybe present on the capstan shaft.
You’ll then need to remove the circuit board by unsoldering the two solenoids and releasing the plastic clip. This is necessary to remove the reel drive pulley, which is held in by a press-fit lock washer. Pry that off and remove the pulley, taking note of how the pulley is seated into the primary cam gear. You can remove the pulley itself by carefully parting the two arms of its holder until its central pivot bar comes free. You will need to remove the pulley to install the reel drive belt.
Clean everything thoroughly with isopropyl alcohol. Then let it dry and clean it again. This belt residue has a nasty habit of reappearing. It is likely that the residue has made its way into the motors too. To fix that, pry off the motor pulleys by easing them up on ether side using a large flat-bladed screwdriver, and use a pipette to apply drops of alcohol into the top motor bearing. Spin the motor by hand to spread the alcohol, and then turn the motor up-side-down to allow any excess to drain. You’ll have to repeat the process until the motor runs freely and its shaft moves freely up and down. Then apply a few drops of lightweight motor oil to the top bearing, spin the motor to distribute the oil, and add a final drop for good measure before replacing the pulleys. You can disassemble the motors to do a more thorough job, but it’s a risky process and one I wouldn’t recommend without practicing on a couple of scrap motors first.
Replacement belts are available from DeckTech, the only belt supplier I will use after trying every manufacturer and supplier I can find over the last few years. Most of the belts on the market don’t last more than a few months, or have inconsistencies that lead to issues with speed stability. DeckTech belts are well made to high manufacturing tolerances and will equal or exceed manufacturer’s speed specs in my experience, often by some margin.
Set the reel belt around the reel drive pulley, and re-locate it between the plastic arms of the holder. It will take some careful adjustment, but eventually the pivot will lock into place and the pulley should spin freely. Then put the reel pulley assembly back into the mechanism, locating it into the large cam gear. Reinstall the flywheel, and lay the large flat belt over the flywheel with the excess off to the outermost side of the mechanism. Seat the reel drive pulley in its groove and take its excess to the opposite side of the mechanism.
Then take the rear motor plate, and hook the reel drive pulley on first, Set the plate over the rear of the mechanism, and ensure that it is fully seated. Lastly grab the end of the flat capstan belt and set it over the motor, spinning the flywheel to seat the belt around both. This might take a few tries Replace the four screws that secure the rear plate, and the mechanism mounting plate with its two screws. Reinstall the mechanism board, making sure the actuators for the tape switches are correctly seated and re-solder the solenoids.
Bring the mechanism to the front panel and fit the counter belt, which hooks over the groove in the reel closest to the counter and runs in the plastic depression moulted into the front panel. Set it over the counter pulley, and lay the mechanism in place. Screw it down, replace the front panel, wire it up and set the speed with a 3kHz test tape. The speed adjustment is on the back of the capstan motor. It should be possible to achieve a figure within 15Hz (0.5% deviation), I managed to get this machine running within 5Hz (0.16% deviation) of the correct speed which is excellent.
Performance is excellent. I can’t hear any speed instability, and noise levels are reasonably low with a decent output from the PC-OCC head coils giving the playback amplifiers a healthy signal to play with. The sound is on the lively side of neutral, deliberately tuned to add a bit of flavour which works well with pre-recorded tapes.
Recording on SA90s (the only blank tapes I still have) went fine, with decent dynamics and the adjustments, recording sensitivity in particular, helping to minimise tracking errors with Dolby. I still favoured Dolby B over Dolby C, though the Dolby C implementation is less aggressive than many other tape decks so I would consider it perfectly useable.
I appreciated the large transport buttons too, and the easy access to the head azimuth adjustments with guide holes beneath the removable door. Over all a solid, well built deck that demonstrates why many people preferred the single equivalents of a manufacturer’s twin-tape options. The quality of the AD-F50y is worlds apart from the AD-wX929, and the AD-WX727 doesn’t bear a mention in the same paragraph.
Guide price on the used market is £10-20 for a broken one depending on condition, £35-40 for a working example that hasn’t been serviced, and £60-100 for a serviced example depending on the quality of the work, the condition of the machine, and original box or instructions. For that money you can have a very respectable Technics, a Sony or a Denon, all of which I would probably still buy over the Aiwa. But the AD-F500 has proven itself to be comparable in performance and they are good value on the used market for the right price.