Lisa 2 Video Problem

From: Jeff Hellige <jhellige_at_earthlink.net>
Date: Sun Apr 7 15:55:17 2002

> > The first thing to do would be to pop the top off of the Lisa
>> and check the 4-5 video adjustment dials along the top of the video
>> board, as well as the adjustment pot on the PSU. To me it definately
>
>Please don't!. If you have a real fault (and this sounds like one), it
>will not be cured by making adjustments. Once you've twiddled everything
>you will still have to cure the real fault and then re-align everything.
>The only times you should adjust presets are (a) after some other person
>has been fiddling about and (b) after replacing components in the
>relevant part of the circuit. And to twiddle PSU presets without knowing
>just what you are doing is a good way to wipe out the entire set of chips
>in the machine.

        The adjustment pot on the PSU I was referring to is part of
the video adjustment. It's reached from the rear of the machine
through a small hole in the back panel. Changing it's value is
actually part of the video alignment procedure after replacing the
video board or adding the XL screenkit modification. The pots on the
video board itself may also drift and need to be readjusted. This is
easily done by 'eyeballing' the video output as you would with the
vertical and horizontal sync adjustments on another monitor or TV. I
once had to open up a early Panasonic multisync monitor and do this.
Everyone else thought the monitor was bad due to it being totally out
of sync.

        Jeff
-- 
                           Home of the TRS-80 Model 2000 FAQ File
                                         http://www.cchaven.com
                     http://www.geocities.com/siliconvalley/lakes/6757
Received on Sun Apr 07 2002 - 15:55:17 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:34:29 BST