Re: Lisa 2 video problems

Watching some of the guys who restore vintage TVs I've seen these sort of odd problems from bad flyback transformers as well :( I'd check the PSU first though since that's much easier to fix.

-J

On Sat, Jun 28, 2014 at 10:56 PM, Bill Vogel <hightrailrider_at_email.domain.hidden> wrote:

> I'm thinking that there is a problem in the horizontal blanking circuitry,
> the link that goes from the
> flyback transformer to the video. (R16, CR4, etc.) Maybe an open cap is
> allowing the blanking
> signal to 'ring'? If you have an oscilloscope it would be useful to look
> at the signal in that area.
>
> Hope that is helpful.
>
> Bill.
> :-)(((
>
> On Jun 28, 2014, at 5:12 PM, James MacPhail <gg__at_email.domain.hidden>
> wrote:
>
>
> Examples of Ken's Lisa symptoms are here:
>
> http://members.shaw.ca/sigmaseven/boylephoto1.JPG
> http://members.shaw.ca/sigmaseven/boylephoto4.JPG
>
> The symptom is the wide dark vertical bars at the left third of the screen
> (ignore the gibberish image in the second picture).
>
> I suspect the problem is related to the +28V supply on the video board,
> but perhaps someone knows more specifically what part needs to be changed?
>
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-- 
Jason Perkins
313 355 0085

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