Date : Mon, 15 Aug 2011 08:37:22 +1200
From : car@... (Chris Reece)
Subject: Advice on restoring a dead Beeb?
Wow, what a flood! Sorry for the delay in response -- on call this weekend,
bit busy. I'll go back through the list mail later and make sure I mop up
the rest of the questions asked, but for now...
On 15/08/2011, at 4:32 AM, Rick Murray wrote:
> On 14/08/2011 15:14, Peter Coghlan wrote:
>>>
>> Ah, I see. I somehow assumed we were discussing power up only but on
>> rereading the original post, I see Chris says "reset" which suggests
>> powering on or pressing break.
> Yup, it's a bit ambiguous, but useful for diagnostic as the reset
> appears to start, but not complete.
Power on. I'll establish what the behaviour is with a break-induced reset.
(All I recall from when I tried it without a logic probe to watch was "nothing
happens" so I'll need to do that again just a little more rigourously.)
> Indeed - are we getting as far as initing the display? Flashing cursor?
> Stuck? Gibberish?
Excellent question; one with an answer that more studly nerds may be able
to decomplicate.
I have British Beeb here, and an old NZ portable TV given to me by a colleague
with some muttered warning about how the UHF spectrum here is different
to that in the UK. I did, of course attempt tune the TV in (after disconnecting
speaker to get rid of that hideous droning noise and the best I could do
was a black and white (yeah!) barbershop pole type display. More black than
white, could have been a flash cursor. Or next week's winning lottery numbers,
who knows.
>
>
>> Sure, but I don't think Chris has said what is written on it. He does
>> say ROM but it is not clear if he is distinguishing between ROMs and
>> EPROMs either.
>
> No, he identified the MOS by removing it, as the only labelled one was DFS.
Wait up -- I took a picture the very first time I opened it. Mobile phone,
poor quality, but I'll dig it out. Here:
http://jessies.org/~car/misc/20110815-bbcmicro/IMG_0994.jpg
There are two identical ROMs (in appearance) in the bank of five, and I
foolishly pulled all three ROMs (one labelled DFS) when I did my reseatathon.
I couldn't determine which of the two doppelgangers was which, but my fuzzy
knowledge and a paw through some manual (yet to be identified) they must
be MOS and BASIC, no?
And getting "further" by flashing lights diagnosis, I assumed that they're
now in the right order.
> Chris - if you are reading - do you have a video camera, decent digital
> camera or mobile phone? Could you record it powering up twice - once
> aiming at the keyboard LEDs, and once recording what (if anything) is
> shown on-screen? Drop it on YouTube, let us know the URL. Then we can
> see/hear its behaviour.
I certainly can, and please accept my apologies for not quite keeping up
with this after asking the question -- I was waiting for a lull and some
matching spare time. Still waiting for that spare time.
;)
Cheers,
Chris.