Tuesday, July 10, 2018

All Hands on (Tape) Deck! - CPCs Part 2

I am constantly amazed by how quickly time marches by. In the blink of an eye we went from arguing whether the Spectrum or the CBM64 was better (the Speccy obviously - I mean, c'mon) to arguing about whether iPhone or Android is better. The more things change, the more they stay the same...

In the same way, how we handle data storage has changed dramatically. As my brain sees it, this has played out over the last couple of years or so. As reality sees it, this has played out over the last three and a half decades. 

When we got our first computer - a shiny ZX Spectrum Plus - it required programs and games to be loaded via tape. This was fairly standard for most home micros of the time, at least in Europe. Our US cousins tended to use discs instead, the reasons for which are debatable.

Anyway. Tapes. Tapes were generally reliable, they were definitely cheap and absolutely sloooowwww. With a typical data transfer speed of 1535 bits per second, it took about five minutes to fill 48 Kilobytes*

*A note about units. I've said it before, I'll say it again. A kilobyte is 1024 bytes. It is not 1000 bytes. A 'kibibyte' is a steaming pile of horseshit dreamt up by someone who clearly couldn't understand powers of 2. So there.

But tapes were cheap, relatively easy to mass produce and, good news for all us schoolkids, monstrously easy to copy. Not that I ever did that...nope, no siree, not me.  To my 12 year old son it seems quite quaint to have a bulky mechanical extension attached to the side of keyboard. And, oh, the horror of having to wait up to five minutes to play a game (I suspect he has never measured how long it takes to get the average PS4 game up and running).

I digress. The CPC464s that I have, have been re-assembled and had some limited testing. They appear to work based on my 'heath-robinson' video cable (yes it's a couple of bent bits of wire pushed into the correct pins with a phono plug on the other end). On the banged up one (which I shall refer to as 'Bert') a tape will play as soon as 'play' is pressed - sometimes. On the one that is in slightly better condition (which I shall refer to as 'Ernie'), the load sequence has to be initiated before the tape will start to play. Curious.

Nicking a composite output...
Also, Bert's deck sometimes won't rewind unless the button is given an extra stab, and the tape counter reset button on Bert is smashed to pieces. I think we can safely say which end hit the floor first when Bert was clearly dropped.

Ernie's deck seems to be OK in that all functions work without issue. The tape counter is fine on Ernie. I suspect Ernie just needs a new belt.

Time to put my repair pants on.

Getting the tape deck out requires the removal of a lot of screws. And the power switch. And the volume control. And the keyboard... Actually, you can get away with not removing the keyboard if you de-solder the power LED from he cassette control board. So, once you've done that the whole thing lifts out of the case.

Complete unit. LED removed from case (not desoldered)

Both decks needed a darn good clean. Isopropyl alcohol and cotton buds. Enough said on that. To cure the slightly hesitant rewind on Bert I got a small piece of 1000 grit sandpaper and very gently rubbed it between the flexible switches on the unit. This worked surprisingly well and rewind now works first time, every time. It also cured the accidentally intermittent 'play'.

Flexi-switch - now works properly.
There is another definite fault on Bert's tape deck. A previous owner has soldered two wires together from where one the flexible switches makes contact. I tried putting them back the way they should be but then the tape deck didn't play at all, so I put it back the way it was originally. I'll just have to live with it. Strangely, the relay in the deck still clicks when the CPC is trying to start or stop the tape but, with the wiring modified the way it is, it just keeps on playin'.

Blue & Purple wires are linked. Hmmm.
On Ernie, I noticed that the pinch roller had a dent in it. I realised that someone must have pressed the play button and left it in that state for some time. This dent resulted in a distinct wobble to the sound every second or so. It didn't affect the loading of the game I managed to record to tape (Harrier  Attack - purely for testing purposes ;) ) but was very, very noticeable. This was a pain as I intended to sell Ernie on to help re-coup the initial outlay on my bundle. I began to wonder if I could swap the pinch roller over.

After imagining being neck deep in mechanism bits and springs and washers I decided, what the heck. If I could remove it easily enough from Bert then I should be able to do the same with Ernie. Fortunately, I was correct to have a go at this. The pinch roller was held onto a plastic shaft by a simple plastic pin that pushed into the top of the shaft. Gently prising it up allowed it to pop off without any drama. I repeated the same on Ernie and immediately installed the non-dented pinch roller in about ten seconds. Easy. Certainly easier than I originally expected!

While the dented pinch roller was out of the deck I attempted to squish it back into shape before re-installed in Bert. Bert will be staying with me so I have no problem with a bit of a 'wobble' from physical tapes. I managed to make it a little better but then decided to go all out and sand it down a bit. (*Imagines the gasps of horror from CPC aficionados...*). It actually worked quite well. The rubber is starting to perish and so I had to be careful not to take too much off or knock chunks out of it.

Now, the main event. Both decks need new belts and, as luck would have it, the chaps at Retro Computer Shack had a twin pack of belts for only a few pounds. Installing them is relatively straightforward, if a little bit fiddly. On the underside of the deck, simply undo one retaining screw, lift the arm and pull out the old belt. Fitting a new one is the same, in reverse. This took about five minutes on each deck and the new belts are nice and firm and grippy. Nice.

Beltin'

Repair action shot.

The buttons also required some attention as they were really dirty. To get them off is also fairly simple. Remove the circlip at the end of the shaft that runs through the buttons. Carefully remove the shaft and the buttons should drop. Then carefully remove each button from the frame. There a tiny springs, three in total, on the bottom part of the buttons that stops them rattling around when they are 'on'. Try not to lose these! They have a habit of pinging off when you remove the buttons so be careful!

Pingy springs - easy to lose, impossible to find again...

The buttons were soaked in soapy water and cleaned with an old toothbrush. Isn't everything? ;)

While I was at it I decide to have a look at the broken tape counter reset in Bert. The button had snapped off the end of the wedge that pushes against the counter mechanism. I tried to fix this with superglue and a small piece of wire across the previous break to give it some strength. It sort of worked but the mechanism is quite stiff and I suspect that the repair has partially failed. It's OK though, as it's more cosmetic than anything and I intend to use an input mod to load stuff up so I won't actually need the counter to work properly.

Before (partially) successful repair.
At this point Ernie is complete. Captain obvious alert. Re-assembly of the CPC is the reversal of disassembly. No great shakes, just a lot of screws... but Ernie is ready to be sold to his next owner.

Bert is getting a little extra something. The thing is, I have no tapes. Or at least, I only have one tape that I've managed to get a working copy of Harrier Attack on to. To allow me to load tapes when I don't have tapes I shall add an input socket. This is easy enough to do by soldering a couple of wires to the tape head and feeding those wires to a 3.5mm socket. By using a 3.5mm plug to 3.5mm plug cable I can now feed sound directly into the CPC from my PC. See?

Wires connected to the head.

Epoxy'ed into place. 

Exterior view - looks almost factory.


Wide angle view.
Using a simple cable and a piece of software called 'CDT2WAV' I can now load any game. It's not perfect as I have to still press play on the tape deck and, of course, the games still load at uber-slow speed. But at least I can play them!

I've really enjoyed playing with the CPCs. They're surprisingly well built and are refreshingly simple in their construction. I'd highly recommend you get one of these if you're looking to start a retro collection as they are easy to work on and, in the main, the only bits that fail are the tape drive belts.

The Speccy's still best though.


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