[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

>>

>>

>>

>>

>>

>> -- 

>> Coco mailing list

>> Coco at maltedmedia.com

>> http://five.pairlist.net/mailman/listinfo/coco

>>

>

>

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