Need Help: Magnavox CM8502 monitor

C

CM850240

Guest
Hi,

I'm definitely not an expert in this stuff so any help would be greatly
appreciated. I have a question about my Magnavox CM8502 monitor (the
Phillips-made, scaled down C=1084). It works fine for about 5 minutes. Then the
picture begins to slowly darken until it's totally black. I found if I tap on
the brightness dial, the picture brightness returns to normal for a few minutes
or seconds. Is it possible for a potentiometer to malfunction from heat? I was
under the impression that chips usually were the parts affected by this. The
TDA3563A video chip is very close to the brightness pot. Could the chip be the
problem instead? Not sure why tapping would temporarily fix it though.... The
solder looks good on the pot, BTW. Also, I heated the metal sides of the pot
with a soldering iron while testing the Ohms with a voltmeter. There was no
drastic change (from 2.41 to 2.37 with the meter set to 20K).

Anyone know a good place to get TDA3563As cheap (if it needs replacing)? I
found one place with them listed at $13 each.

Please email me at CM850240 ... at ... aol.com

Thanks

Thanks
 
"CM850240" <cm850240@aol.com.junk.co> wrote in message
news:20031031155728.06392.00000083@mb-m19.aol.com...
Hi,

I'm definitely not an expert in this stuff so any help would be greatly
appreciated. I have a question about my Magnavox CM8502 monitor (the
Phillips-made, scaled down C=1084). It works fine for about 5 minutes.
Then the
picture begins to slowly darken until it's totally black. I found if I tap
on
the brightness dial, the picture brightness returns to normal for a few
minutes
or seconds. Is it possible for a potentiometer to malfunction from heat? I
was
under the impression that chips usually were the parts affected by this.
The
TDA3563A video chip is very close to the brightness pot. Could the chip be
the
problem instead? Not sure why tapping would temporarily fix it though....
The
solder looks good on the pot, BTW. Also, I heated the metal sides of the
pot
with a soldering iron while testing the Ohms with a voltmeter. There was
no
drastic change (from 2.41 to 2.37 with the meter set to 20K).

Anyone know a good place to get TDA3563As cheap (if it needs replacing)? I
found one place with them listed at $13 each.

Please email me at CM850240 ... at ... aol.com

Thanks

Thanks
Click to expand...
Sounds like a cold solder joint.
 
This sounds more like a cold solder connection, or something is mechanically
not making contact or defective. I would not think it is the IC, unless the
IC was mechanically intermittent inside, which is very rare.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"CM850240" <cm850240@aol.com.junk.co> wrote in message
news:20031031155728.06392.00000083@mb-m19.aol.com...
Hi,

I'm definitely not an expert in this stuff so any help would be greatly
appreciated. I have a question about my Magnavox CM8502 monitor (the
Phillips-made, scaled down C=1084). It works fine for about 5 minutes. Then
the
picture begins to slowly darken until it's totally black. I found if I tap
on
the brightness dial, the picture brightness returns to normal for a few
minutes
or seconds. Is it possible for a potentiometer to malfunction from heat? I
was
under the impression that chips usually were the parts affected by this. The
TDA3563A video chip is very close to the brightness pot. Could the chip be
the
problem instead? Not sure why tapping would temporarily fix it though....
The
solder looks good on the pot, BTW. Also, I heated the metal sides of the pot
with a soldering iron while testing the Ohms with a voltmeter. There was no
drastic change (from 2.41 to 2.37 with the meter set to 20K).

Anyone know a good place to get TDA3563As cheap (if it needs replacing)? I
found one place with them listed at $13 each.

Please email me at CM850240 ... at ... aol.com

Thanks

Thanks
 
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