Re: PET 50Hz vs. 60Hz screens?

Check the display signal connector on the mother board.  If this does make 
good contact, it can cause jitter in the display.  Otherwise, check C27, 
C28, and C29 on the display board.



On Fri, 21 Dec 2012, MikeS wrote:

> Replacing the 60Hz 901499-01 ROM in a 60Hz Fat 40 with the 50Hz 901498-01 
> version works, but the screen has a slight but annoying jitter; I suspect 
> it's due to the proximity of the power transformer to the monitor.
>
> mike
>
> ----- Original Message ----- From: "Groepaz" <groepaz@gmx.net>
> To: <cbm-hackers@musoftware.de>
> Sent: Friday, December 21, 2012 12:09 PM
> Subject: Re: PET 50Hz vs. 60Hz screens?
>
>
> On Friday 14 December 2012, you wrote:
>> The question is, what is a "valid" timing?
>> 
>> Can an originally 60Hz screen run with a 50Hz timing and vice versa?
>> (I'm not talking about the line frequency here)
>
> thats really hard to answer without knowing hard technical facts about the
> screen :) depending on manufacturer this kind of info is written on the
> backside even, or maybe on the board (certainly its mentioned on the
> schematic
> that you can find in lots of old TV sets).
>
> practically i'd say however that any monochrome screen of that time can sync
> to both 50 and 60 hz. if in doubt try it out =)
>
>> The question is, can say a 50Hz program or demo run on a 60Hz machine, by
>> just reprogramming the CRTC appropriately, without damaging the screen?
>
> although in theory it is possible to damage the screen with improper
> timing -
> it is more than unlikely this will happen because of 50 vs 60 hz -
> personally
> i would ignore this "problem" alltogether :) if it makes funny noise, just
> switch it off quickly though =P
>
> -- 
>
> http://www.hitmen-console.org    http://magicdisk.untergrund.net
> http://www.pokefinder.org        http://ftp.pokefinder.org
>
> Mein Humor ist so elitär wie euer Gehabe!
>
>
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>
>
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>

wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

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