Date   : Sat, 22 Oct 2005 11:06:43 +0100
From   : "Ian Wolstenholme" <BBCMailingList@...>
Subject: RE:

I'm happy to erase EPROMs for anybody who wants to send them
to me.

Best wishes,


Ian

----- Original Message -----
From: David Hunt
To:  <bbc-micro@...>
Sent: Fri, 21 Oct 2005 00:09:50 +0100
Subject: RE: [BBC-Micro]

> I think they all work the same way.........

Yes, it is a tried and tested way of using a single microswitch for the
whole space-bar that gives the user the luxury of not having to press it
exactly in the centre. Most PC keyboards have this arrangement on other
larger keys such as Enter and Shift.

On the Beeb this is taken care of by two small, thin pieces of plastic with
a hole in the bottom. What works for me is to insert the plastic lugs into
each end of the space-bar key. Then let rest over the holes where the piece
of metal is, then using a screwdriver, lift the metal rod level with the
hole and then move a space-bar lug hole over it. Now to get the other side
in push the metal rod as far as possible in the other direction, this will
move the space-bar over a bit, but that's what you want. Then gently lift
the metal rod level with the hole and move it over just enough so it is
inside the hole. Now gently align the space-bar with the microswitch key and
press down on it. Then you should end up with a perfect space-bar again.

I've done this soooo many times that it all happens in a blink of the eye,
almost like a Ninja!

> >
> > 2. My Solidisk EPROM burner does not burn EProms? I
> > have been using the correct size EPROMS and correct
> > orientation when I insert them. I have been following
> > the instructions re: when to turn Vcc and Vpp on, etc.
> > The lights do come on! The EPROMs are old though. Am I
> > supposed to pulll off the sticky cover over the EPROM
> > window when I try to burn one? Can you just keep
> > burning over the same EPROM, or do you require a new
> > one every time?
> >

You problem is likely related to the fact you haven't erased the EPROM yet.
In order to do this you need to get an EPROM eraser. Basically, this is a UV
light in a box with a timer. They're pretty cheap, eBay or a local
electronics store will have them. 

Perhaps there are hobbyists in your area who might erase some for you. The
life expectancy i.e. number of write cycles varies depending on the
materials used in manufacture. Over time, these materials and the
manufacturing quality improved so many more cycles are possible. You should
expect at least 200 cycles even from early 80s devices, but well over 1000
cycles on modern devices.

Dave ;)