[TechAssist] Re: Magnavox GS 9P6040-C102 PTV-843
- From: "G.Larkman" <mail@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 26 Oct 2004 12:11:12 -0700
Dave,
Chassis - PTV-843
Model - 9P5540 C102
Brand - Magnavox Projection TV
Symptom....- turns on with green light then shutsdown. Breif build up of HV.
Clue - unplugging the convergence module power supply harness allows set to
fire up with no convergence correction and postage stamp picture on all 4
sides.. Note. not bad C/G IC's. the board is
simply loading down the main power supply. Further checks reveal 130V rail
is dropping down to 94 V and then shutdown with additional load of CG panel.
Fix - This is an unusual SMPS in as much as it has two controllers, one
on the hot side and the other on the cold side of the supply.
There are 4 opto couplers and opto IC loc # 7412, part #483520988561 had
become thermally sensitive and caused a lack of regulation..
Freezing it with a frozen Q-tip (another Nesda learned trick!) would cause
the 130V rail to plummet.
Replacing IC led to rock solid 130V rail.
NOTE. also check resistor R3456 / 510Kohm for drifting.
Thanks to Jeff at Intrepid for his assistance with a schematic. (was on B/o
forever)
Glenn Larkman
Audiotech
256 Nth Hwy 101
ENCINITAS CA 92024
760 944 9048
FAX 944 0345
mail to"mail@xxxxxxxxxxxxx"
"www.audiotech.net"
----- Original Message -----
From: "peggs" <peggs@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>; "Tech Line" <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, October 26, 2004 12:50 PM
Subject: [TechAssist] Re: Magnavox GS 9P6040-C102 PTV-843
Try Heat/Freeze on the Opto's in the Power Supply.
I think this is the chassis having trouble with those.
Peggs
At 09:57 AM 10/26/04, TV Man wrote:
>Picture comes in on all 4 sides till you have about the size of a 25" TV.
>If you leave it like that it comes back to normal in about 15 min. Never
>worked on this model before and I have no shop, so I have to repair in
>home . Any help would be appreciated. Thanks, Dave
>TV Man
>P.O.Box 654
>Inverness, Fl. 34451
>
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