Archaeology [Aiwa AD-R450]

Archaeology. The process of digging up old things and trying to understand them. In this case, my old Aiwa AD-R450 cassette deck, which was an excellent machine until one day it stopped responding to some of the panel controls - apparently a logic fault in the soft-touch circuits. I got another deck but, as is my way, I archived the old one until I could find the time to look at it.




The big feature of this one is the "Quick Reverse" function. The erase and rec/play heads are mounted on a tiny turntable and there are two capstans and pinch wheels. Reversing the tape direction involved engaging the other capstan and flipping the turntable round, which could all be done in 0.2 seconds thus enabling playback or recording both sides of the tape without an audible gap.

The picture above is courtesy of www.radiomuseum.org, a mine of information.

Unfortunately this unit has been in storage for around 20 years, so the belts are pretty well liquid. In fact I found only a small portion of the tape counter drive belt and the main capstan drive belt was all wound around the motor pulley, like self-amalgamating tape, and it had melted into an impenetrable tyre of rubber. I had to cut it off so the only info I have is that it's 5mm wide and is made of the same stuff they used for the belts in the AD-F770 and AD-F660, which also have liquefied (both of these being repaired currently).

The logic seems to be doing its stuff, but it's clear that the deck function depends on mechanical drive to move the heads and drive the tape. The reel motor is separate so the tape will fast wind OK but it needs a new main belt. I have no service info on this as yet, but I think the belt probably wrapped around the > flywheel and drove the < flywheel off its back, so that they revolved in opposite directions. (The motor only goes one way no matter which direction is selected). So the next step is to confirm this, if possible, then measure the path length of the belt and find a replacement. I also have to work out where the other end of the tape counter belt was driven from and find a new one of those; then I can think about dismantling the mechanism and fitting them. After all that I may have a working cassette deck (which nobody wants!). But I like seeing things working again.

 I suspect that when I first encountered the fault the belt was loose, and may have driven one flywheel but not the other. This may have given me the impression that the logic was wrong, as the deck would have run in one direction but not the other, and the heads wouldn't flip. If I could see the motor running and the flywheel turning I would have thought it was OK and the fault must be in the logic circuits; I knew less then about how much functionality still depended on the mechanical motor power in the designs of the day.

And I've got a horrid cold and cough today.