[Coco] FM-77AV video sync problems

[George's Coco Address]

Gene Heskett,

  Since you are(as far as I'm concerned) the guru on raster scan television, 
I have a question..

  I am confused about the power line frequency and how it relates to 
television. All the TVs I've worked on convert the incoming AC power to DC, 
switch it to AC(almost), goes through a transformer at a high 
frequency(efficiency), and then converts it back to DC.
 All our cocos convert the incoming AC power to DC, albeit a lower voltage. 
If  a matching computer and monitor are used on a power frequency(50 or 
60HZ), how can they have problems with sync, when there is no reference to 
the AC power frequency coming in?
  I can understand power supply problems when operated at incorrect 
frequencies, such as a transformer that is supposed to work at 60HZ vs. 
50HZ.

George



----- Original Message ----- 
From: "Bob Devries" <bdevries at gil.com.au>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Tuesday, April 11, 2006 8:27 PM
Subject: Re: [Coco] FM-77AV video sync problems


> Searching the web shows that Japan in fact uses both 50 and 60 Hz @ 
> 100VAC.
>
> http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_and_frequencies
>
>
> This being the case, it could well be that the FM-77AV is set for 50HZ 
> operation. This would definitely cause serious rolling of the picture if 
> used with a 60HZ monitor.
>
> This is the problem we Aussies faced when OS9 Level 2 came out. The GIME 
> was programmed for 60HZ operation in the boot, and when used on a TV that 
> did not have any H & V adjustments, it was very difficult indeed to get it 
> to work right. Even when using the CM-8 monitor, the Horizontal and 
> Vertical adjustments were all over to one end of the potentiometer range.
>
> --
> Regards, Bob Devries, Dalby, Queensland, Australia
>
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
>
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
>
> ----- Original Message ----- 
> From: <KnudsenMJ at aol.com>
> To: <coco at maltedmedia.com>
> Sent: Wednesday, April 12, 2006 11:08 AM
> Subject: Re: [Coco] FM-77AV video sync problems
>
>
>>
>> In a message dated 4/9/06 3:53:28 PM Eastern Daylight Time,
>> linville at tuxdriver.com writes:
>>
>>>I  suppose this could be a 50/60Hz issue...?  What is the power  cycle
>>>rate in Japan?
>>
>>
>>
>> Pretty sure Japan is 60 Hz, same as North America.  But you're right, 
>> the
>> voltage is lower, nominally 100V to our 117.
>>
>> When you play with the sync hold knobs on the monitor(s), is one extreme
>> rolling slower (ie, closer to sync) than the other extreme?  It sounds 
>> like  your
>> horiz sync is OK, it's the vertical.
>> Maybe the sync pulse polarity is wrong, but then, you should be able to
>> "stall" the image in the center for a few seconds with the Vert Hold 
>> knob.
>> --Mike K.
>>
>>
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