Date : Fri, 01 May 2009 12:34:50 +0100
From : bbcmailinglist@... (Ian Wolstenholme)
Subject: Microvitec Cub Monitor Adjustments
Thanks for this - in view of the warning, I don't think I'll be fiddling about
much inside these monitors. I had an idea the "convergence" might be
something to do with the rings on the back of the tube, I reckon I'll just
have to live with it ("live" being the operative word!)
Best wishes,
Ian
----- Original Message -----
From: Mark Haysman [mailto:jumbos.bazzar@...]
To: bbc-micro@...
Sent: Thu, 30 Apr 2009 18:42:17 +0100
Subject: Re: [BBC-Micro] Microvitec Cub Monitor Adjustments
Hi.
The focus drift is the Tripler on it's way out. It may be the pot, but it's
usually the divider network inside the tripler block. If it's a good
monitor, like a 1441 or a 1451 with a nice tube, then it's worth replacing
the tripler. I got some of the green ones from www.n-tronics.com, they are
about ?30.00ea with the shipping.
Adjusting the convergance is not for the faint-hearted! But as long as you
mark your starting point, you can always go back to it. At the rear of the
tube, between the base board and the yolk are a set of 6 rings, in 3 groups
of 2. The front 2 adjust the purity,and the other 4 adjust the convergance.
You need to loosen off the clamp in order to move them. I don't have any
specific guidelines on adjusting them, I would suggest taking a black marker
pen, and draw a line across them, so you know where they were originally,
then you can move them about, and if you mess it up totally, you know where
to go back to. It may be that the convergance is the best it can be, some
tubes were better than others, the color mask inside the tube can warp over
time - I've seen 1451s that look pants next to an identical model that has
100% convergance.
Those little RGB pots on the base board are to do with color drive and bias.
One final thing, when you do the convergance, be careful not to blow
yourself up! You will get a tingle if you touch the wires to the yolk, a
hard slap if you catch the focus connector to the tube base, and a hard slam
across the room if you catch the HV cable! Also, remember the main board has
exposed mains on it.
Mark.
----- Original Message -----
From: "Ian Wolstenholme" <bbcmailinglist@...>
To: <bbc-micro@...>
Sent: Thursday, April 30, 2009 6:28 PM
Subject: [BBC-Micro] Microvitec Cub Monitor Adjustments
I've been trying to adjust the two Cub monitors I have connected to
Stations 200 & 201. Station 200's monitor gave up the ghost a while back,
just giving an unsteady picture flickering to the left and right. I managed
to fix this with the help of the service manual which told me which thing
inside to adjust and it's now back.
Whilst I was inside fiddling about I also altered the focus which resulted
in a much sharper picture.
However, I've noticed today that the focus has drifted back to how it was
before. It's not bad, but it's nowhere near as good as it was last night
when I twiddled the focus knob inside.
Is this something to do with the monitor warming up or can I find a
permanent solution?
With the other monitor, the focus has always been very bad and there is
some colour blurring. Text leaves a blue shadow to the left of characters
on the screen. It's all right in the very middle of the picture, but very
noticeable around the four edges of the screen. I couldn't find anything
in the service manual which appeared to address this and I've tried
twiddling
with the little holes marked R, G & B (of which there appear to be about 7)
on the board fixed to the back of the tube, but these just seem to affect
the overall colour.
Although I've improved the sharpness a bit with the focus control, it's
still
pretty bad and is practically unreadable in mode 0. Can I do anything to
improve this?
Best wishes,
Ian
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