Date   : Mon, 05 Dec 2005 19:49:46 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Domesday

Richard Gellman wrote:
> 
>>> Now the hard part: One Philips VP-415 LVROM Player.
>>> This is actually a VP405, with a hack
>> Quite some hack ;)
>>
> 
> No kidding. You should see inside one.

I've been inside more of them than I care to think about :(

 > It literally is a VP405, with bits
> added. The days of wires being trailed between components "to make things
> work" suddenly come flooding back.

Actually, later ones were much improved. Still bodge-like, but less of the 
trailing wires. When I say "much improved" I mean "still bloody awful" of 
course - PCB assembly quality was still about the worst I've ever seen in 
anything. A shame, as technically they're extremely good, with all sorts of 
built-in diags and the like.

> They even had to upgrade the power supply to accomodate the SCSI board, as
> the VP405s wasn't beefy enough, and even then the "new" PSU had bodges
> fitted to increase reliability. This is why so many VP415s die easily, they
> are a *very* large hack ;)

Not to mention that they have all those vertically mounted boards inside 
beneath the tray assembly - you can't diagnose individual board faults with 
the tray assembly in place, but you need the tray assembly in place to play 
anything in order to diagnose board faults :)

I ended up soldering up a bunch of short flying leads so that I could have 
boards hanging outside the case whilst testing...

> Re: Trackerball, Marconi does ring a bell thereof. 

Yes, I'm not sure what else they were used for. I can't imagine Marconi went 
to the expense of building them just for the Domesday project, so I imagine 
they must have been used somewhere else beforehand (possibly a spin-off of 
some defence project?)

> But I haven't seen many
> trackerball units floating around, so in the absence of one, a standard AMX
> mouse could be rigged to simulate one (probably a better idea too,
> considering how we are mostly accustomed to mice now).

Actually, most of the Marconi units seem pretty worn out anyway - the X/Y 
shafts seem very prone to wear inside. No doubt because as kids we all gave 
the ball a good spin whenever walking past them :-)

> For those interested in a few nostalgic statistics, you may be interested to
> know, that the 12" laserdiscs had a 324Mb data capacity, shared with a
> 54,000 frame video capacity.
> 
> By shared, this means a data area and a video frame can not co-exist in the
> same physical place.

Yes, 324MB *and* 54,000 frames capacity on the same disk, just to clarify.

I just dug out some of my Domesday info - I'd forgotten that it was Logica who 
did all the software work.

Oh, I found a nice news snippet from December 1981 the other day about Philips 
  delaying the UK launch of video disks - and industry analysts speculating 
that the technology was both too late to market and too expensive to be 
seriously used anyway. I suppose ultimately they were right, although it saw a 
few years of service...

cheers

Jules