Not too hard [Aiwa AD-M100K]

Yesterday I turned to resurrecting the Aiwa AD-M100K stereo cassette deck. This is quite a nice straightforward machine but the design is very much of its day (1980) and showing its age. It has mechanical tape loading via piano keys, single direction transport, analogue VU meters and no frills. But it was typical of the kind of stuff I was using at the time.

This one had toffee drive belts and although the motor hummed, that was all. I couldn't find any service info but the nice people at Vintage Cassette have a spec sheet here.

After lifting the lid I did some measuring using the tested method of wrapping ribbon round the belt path and overlapping it, then cutting both ends together. This gives the length but be careful, some suppliers quote "length" meaning the belt laid out in a line but still intact - so their "length" is simply half of the measurement. Other suppliers use the diameter of the belt in a circle as "length", including CPC Farnell who complicate matters by referring to the height and width of the belt, meaning the width and thickness as I would call it. But hey ho, it keeps the brain from coagulating I suppose.

This deck needs four belts, which I got from CPC as follows:

Capstan belt: AVBELT4 - flat, 69mm dia, 3.5mm wide, 0.5mm thick
Auto-stop drive: AVBELT78 - 38mm dia, 1.2mm square section
Tape counter primary: AVBELT92 - 52mm dia, 1.2mm square section
Tape counter secondary: AVBELT66 - 28mm dia, 1.2mm square section

These are just what I could find which worked - there may be others. You can pay a lot of money for a dedicated set of belts specifically for this machine, which might just be these ones re-packaged with a fiendish markup. I notice the 'set' suppliers never list the belt sizes in their kits!

The tape transport mechanism can stay in place - I just removed two screws (mid left and bottom right, out of direct sight) which allowed the backplate to hinge away and give space to thread the capstan belt through, followed by the auto-stop belt which runs off a coaxial pulley on the flywheel. I then re-fixed the backplate and fiddled for ages to get the two belts around the flywheel rim/motor pulley and the flywheel pulley/autostop pulley respectively. Then check that it all worked - success! Pretty well everything on these is done mechanically so once the drive is back, only the tape counter didn't work. This could have been tricky but there is enough space around the take-up spool hub, where it passes through the front plate, to thread the belt in. You then catch it from behind and stretch it up to the idler pulley top right, and then add the last belt from the idler to the tape counter.

That was all there was to it this time - I spent the next hour or more listening to Pavarotti's Greatest Hits (Decca K236K 22, 1980) which was very appropriate, just the kind of thing I might have played on it in 1980. It works beautifully. While I listened I put together a full description for the blog, peppered with snappy witticisms and useful tips. Then when I went to publish it, there was a 'Save error' and Firefox crashed, losing the lot. That's why this account is a bit boring, coz I can't be bothered to do it all again.

(Postscript: I found that using copy & paste doesn't work in the blog for inserting images. The image appears but the uploading during Save or Publish gets a bit sniffy with the Javascript...)

Dolly gets it [Barbie]

Routine and trivial one today - daughter's doll with a broken knee. The movable knee joint had been forced sideways breaking off part of the leg shell which forms a fork for the lower leg to pivot in. Just a matter of reassembling it and clamping after making sure there was no glue on any of the moving parts. For this I used Bostik's "Hard Plastic Glue" which seems to be a form of polystyrene cement. It works very well on rigid plastics and is very fast-setting. Superglue would probably be the second choice. It might still be necessary to fix a wire ring around the joint to support it, but I don't think it's likely.

Much harder to repair are the Barbie dolls. These are now soft-feel and parts are made of a flexible plastic like polythene (I think they use more specific names these days, but to me any waxy plastic is called either polythene or polypropylene). This stuff is a nightmare to glue together - none of the usual adhesives work very well. You might be able to weld it with a hot soldering iron, but that's messy and rarely strong enough. I've had a couple of Barbies who lost their heads (which are usually on a sort of knuckle joint at the neck, with the head pulled into the neck by a strong rubber band) and in one case I had to re-fix the head using a wire secured by drilling a hole in her lower back and blobbing the end with epoxy glue - I decided not to run it directly down to the obvious spot (!) for reasons of propriety. It wasn't pretty but the head was able to move around as before and the clothing covered the end of the repair wire. In the other case the head had to be rigidly glued back with impact adhesive.

It might seem pointless spending time and money fixing broken toys, and maybe by some standards it is. But giving a much-loved toy a new lease on life is a tiny contribution towards saving finite resources and usually means a lot more to its owner than you would think. That's good enough for me.

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.

You've got to start somewhere [Dragonbone]

Well, here I go. My first Blog. It's a strange feeling, because I'm a very private person and I worry about putting stuff out there for posterity - once it's said it can't be taken back, etc etc. The hell with it - I'm old enough not to care any more.....

The idea of this, is that I seem to spend most of my time mending things, which I find very rewarding on several levels. When you have some artifact which isn't functioning in some way, many folk would simply dump it in the bin and buy another. But that's how all the ordinary stuff disappears - have you seen one of those pointy tin openers they used to pierce the Party Sevens? No, thought not. The Party Sevens disappeared and so did the tools - not that it matters much really, but a museum might think otherwise.

Then there's the economics. Mostly, what I mend is pretty worthless and costs more to mend than to buy a new one. But that's without considering the environmental cost, and the emotional value (toys, for example), and the personal satisfaction of overcoming a challenge. There's also, in my case, a pleasure to be had in seeing a machine working as well as it ever did, and often better. So that's why I mend.

Since I spend so much time doing it, I wondered if others might be interested in the work. I often get people marvelling in the ingenuity of a repair or seeing a way to fix their own stuff that they hadn't considered. People also say that most folk don't know how to fix things, and if I do, then maybe I ought to tell them. Not that I do anything special, but I do try to do it properly. Unfortunately I have a bit of Asperger somewhere in me, which leads to a tendency to talk to other people about my personal interests until the glazed look has turned into a murderous stare. Other people can apparently see this but it seems that I can't. I thought that maybe a blog would allow me to vent my desires without offending anyone who can't switch me off.

At the moment I'm working on a batch of broken hi-fi units, mostly cassette decks with soggy belts or other faults. I've also got a toy truck's towing hitch to finish, the fridge to sort out and a shed full of bikes, toys, electronics and other bric-a-brac which all need some kind of attention. I intend to post a snippet every so often about the progress, or otherwise, of these things. Then I can imagine the rest of the world gasping in astonishment, horror, mirth or pity. Actually I'm probably the only one who will ever read these little confessions so it matters not.

 So that's it for now. Next time I'll put some meat in the sandwich, so to speak, and who knows where it will go from there. By the way, the "dragonbone" in my username refers to a device I had once, purchased in Madison (Wisconsin, USA):

....which was basically an electronic dice (die?) which could be switched to have as many 'sides' as you needed. It was for use in Dungeons and Dragons and other like pursuits, games which often used odd-sized dice to decide who won a battle, or how many steps to move. This was before computer games got going. Anyway, it was fashioned to look like a bone with 'jewels' (LEDs) all the way along, and a bit at the end which you twisted to select the sided-ness - so if you selected 12 and pressed a stud, it would light up the LEDs to indicate a random number between 1 and 12. It seemed like a neat name for a neat gadget incorporating wizardry, mystery, oddity and dorkishness. Just like me.