Date   : Tue, 17 Mar 2009 04:40:31 +0000
From   : mike@... (Mike Tomlinson)
Subject: Microvitec Tripler

In article <782037.14757.qm@...>,
debounce@... writes

>One of my Cubs had a 'whiteout' a few weeks ago.? I jogged the pot marked VR932 
>and the screen went dark, then tried to turn it and the whole lot crumbled.? 

Very typical.

>R934 next to it was also burnt around one end.

Change it, R933, and R236 (on the main PCB next to the line output
transformer).  Those all form part of the voltage divider circuit which
sets the A1 voltage.  You should really use 1W metal film resistors for
all three replacements.

If R236 is a 1/2W carbon resistor, it WILL fail.

Standard carbon resistors will work but won't last (they fail in the
manner you described, with a burnt ring or a visible pinhole).  Of
course, on an old Cub which is used intermittently, you may not care, or
not mind changing the resistors when they fail.

>  Farnell no longer stocks the 
>exact trimmer, their suggested replacement is smaller but I improvised some 
>connections and so far it is holding up, although I wouldn't recommend doing 
>this.  (I used a 2.2M part as suggested in
>http://www.astro.ljmu.ac.uk/~bbcdocs/hardware/Microvitec-Series%203%20Colour%20D
>isplays%20Service%20English.zip
>- this may of course be an OCR error!)

No, you're right, it is 2.2M.  Serves me right for relying on my memory
:)

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