Date   : Thu, 19 Feb 2004 17:35:36 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Domesday oddness (difference between model B and Master video

Hi all,

latest on all the Domesday nightmare... :)

Turns out the remaining museum player has cooked its genlock since the
last assessment too (when it used to work until it warmed up). Now it's
dead when cold too. So much for being able to use it as a reference to
fix the others. 

So that's four units we have access to, three of which are fine apart
from the dead genlocks. The other unit is the same too, except it also
has a broken tray position sensor. I've got the video mixer schematics
traced out now at least, but it's slow going!

A curiousity though: I was attempting to use the Master host system to
control the player earlier, hooking the Master up to a normal monitor so
I could see what it was doing. Meanwhile I had a regular BBC B feeding
video into the LVROM.

Odd thing was, the LVROM just wouldn't sync to the disk contents at all
with the BBC B feeding video into it. The player plays video fine with
the Master's video out plugged into it - it just doesn't display the
Master's video signal on screen because of the broken genlock. 

But, what's the difference electrically between the BBC B and the
Master's video output? There must be some subtle timing difference
between the two. I know that BBC B works fine with a monitor, it's just
the LVROM doesn't seem to like it for some reason. 

Odd!

Couple of asides: 

1) both the Master host I have here and the one still at the museum have
suffered from flat NVRAM batteries at one time or another; I do hope
there aren't any hidden settings to do with the video chain which the
Domesday setup manual doesn't cover and would affect the players'
ability to lock onto the Master video output correctly!

2) The LVROM players have an internal battery too; I'm not sure what
settings they retain on power-off. One battery gives out about 2V, on
the other players they're reading less than 0.5V. The batteries are
marked with just a part number and give no indication of what voltage
they should give out :(  Hopefully them being operational is not
critical! 

cheers

Jules