[Coco] Magnavox monitor

[peak at mail.polarcomm.com]

Sounds like a Power supply shutdown problem to me. If B+ 
voltage is a little high the HEW ckt will prevent high 
voltage. Another victim of polititians (Health Education 
Welfare) getting their hands into our circuitry!

Eric 


---- Original message ----
>Date: Sun, 29 Feb 2004 20:44:08 -0600
>From: "Boisy G. Pitre" <boisy at boisypitre.com>  
>Subject: Re: [Coco] Magnavox monitor  
>To: CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
>
>Marty (and all the others who bothered to reply),
>
>Thanks for taking time to help with this problem.
>
>I was incorrect about something, and have to revise the 
description of 
>the problem slightly.  It has been some months since I tried 
it to turn 
>the monitor on, and I actually hooked it up a while ago.  
Here's what 
>actually happens:
>
>When I press the power switch on the back of the monitor, I 
hear the 
>high pitch wine, but as soon as I let the switch go, the 
whine stops.  
>However, the front panel green LED (which indicates power 
on) NEVER 
>comes on.
>
>If I press the power switch again, it does the same thing.  
As long as 
>I hold the power switch down with my finger, I hear the high 
pitch 
>squeal, but the LED does not come on.  Releasing the switch 
always 
>causes the noise to go away.
>
>If I recall correctly, this switch should keep the monitor 
on once it 
>has been pressed.  This does not seem to be happening.
>
>I've checked the fuse and it isn't burnt.  It may be that 
the switch 
>has somehow been rendered ineffective.
>
>I'll put a little more time in diagnosing the problem.  If I 
can't get 
>it to work, then I'll junk it, or send it to someone who 
thinks they 
>can fix it (and it will be theirs).
>
>Boisy
>
>On Feb 29, 2004, at 6:06 PM, Marty Goodman wrote:
>
>> Hi there, Boisy!
>>
>> You PROBABLY are well acquainted with this, and it 
PROBABLY isn't the
>> problem with the monitor you have, but...
>>
>> OLD Magnavox moniotor (8CM series) tended to have cold 
solder joints on
>> their boards, especially those connecting the flyback 
transformer to 
>> the
>> circuit board.  If you meticulously solder-reflowed the 
contacts for 
>> the
>> flyback (and perahaps other large parts connected with the 
high 
>> voltage and
>> medium voltage circuits) it often would fix problems with 
those 
>> monitors
>> characterized by sudden onset of no picture.
>>
>> It's pretty quick and easy to reflow those contacts, so it 
may be 
>> worth a
>> try.
>>
>> Pity it's so hard to ship a monitor... I've a spare Sony 
KV1311CR that 
>> I
>> would like to get rid of!
>>
>> But your description of your problem... with the high 
pitched squeal...
>> suggests you MAY have a dead component.  Perhpas a 
horizontal output
>> transistor, and/or something driving it.
>>
>> Sadly, I have no tech data on the 1CM series.  I do have a 
service 
>> manual
>> for the 8CM series, tho.
>>
>> ---marty
>>
>>
>>
>>
>>
>> -- 
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>> http://five.pairlist.net/mailman/listinfo/coco
>>
>
>
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