Date   : Tue, 26 Aug 2003 08:42:30 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re:

In article <000001c36b24$c4d4a210$6600a8c0@...>, C Alastair Seggie
<alastairseggie@...> writes

>    When initially turned on the picture scrolls from left to right 
>    (looking at the screen) then stabilises with the picture far over 
>    to the left so you can see a small part of it creeping back in to 
>    view on the RHS of the screen. It slowly migrates to the picture 
>    right until it is almost a good picture. =A0Then all hell breaks 
>    loose and it goes back to the scrolling.

At first look, it sounds like the horizontal sync is slightly off.  Go
to:

http://www.8bs.com/othrdnld/manuals/cubmanual/!cub2.htm

and scroll down to the first set of diagrams.  Does the first one
showing the picture breaking up horizontally describe your symptoms?
If so, adjust VR218 - IIRC, this is one of a row of pots at the back of
the main circuit board (closest to the back of the monitor.)  Let the
monitor warm up, display a picture, slowly adjust VR218 one way until
the picture begins to roll, then adjust it the other way until it begins
to roll again.  Then set the pot to the half way point.  That concludes
the set up procedure.

A non-metal trimming tool is preferred.  If you must use a screwdriver,
use an insulated one and keep one hand behind your back while working in
a live monitor.  If you're not comfortable working inside a monitor,
don't do it.  There are lethal voltages and currents present inside,
even for quite some time after power has been removed.

If you cannot get the picture to lock, there is a fault.

> Then all of a sudden it is 
>    fine, the whole process takes about 15-30 min. But even when the 
>    screen is good it is white when the BBC is off.

Very odd.  You say below the board has the "large green box" on the RHS
of the lower circuit board.  This is the tripler module, which
multiplies the 8kV line output voltage to 24kV for the tube.  This means
the monitor has an Issue 3 circuit board.  Issue 3 PCBs should show a
dark screen with no input.

> I have it open and 
>    I found a resistor R231 (the largest one under the CRT) that had 
>    come away from the metal strip that goes to the uppermost lead, I 
>    have re-soldered this but it has made no difference.

R231 is a safety resistor.  The metal strip you refer to is spring
laden.  If an overload condition occurs due to a fault, the resistor
heats up, melting the solder and the sprung connection opens.

The monitor will not work at all with this resistor open (it removes the
power feed to the line output stage.)  If it opens up again of its own
accord, there is almost certainly a fault.  Does the monitor make any
unusual noises?  (clicking, squealing)?

> I may have 
>    actually knocked this off while trying to get the board out. This 
>    one has the large green box on the RHS of the bottom circuit board.

With respect, you don't sound as if you are experienced in electronic
repair, and a monitor is not the best place to start learning.  Could I
suggest for your own safety you take it to a TV shop or scrap it and buy
another?  Cubs are about a tenner secondhand.

Mike

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