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CRT TV Mitsubishi CT29AS1 Vertical deflection problem?

Gpit6903

Jan 25, 2020
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Jan 25, 2020
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Hi all

I've been scratching my head for days to work this out.

My mitsubishi Crt TV CT29AS1 has gradually deteriorated. The top 1/3 of the picture is stretched. If I display a service test picture for geometry the circle ends up looking like an egg at the top. I have the service manual and have tweaked the service mode. However, I cannot adjust anymore.

Can someone help me by advising if it is the vertical deflection circuit and a bootstrap capacitor before I take it all apart and discharge?

Any advice would be amazing!!

Thank you

G
 

Gpit6903

Jan 25, 2020
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Jan 25, 2020
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I have no dismantled the TV and discharged it. Before I start recapping the whole board can anyone advise me of the deflection circuit and usual problems or capacitors that might go?
 

Gpit6903

Jan 25, 2020
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OK great thanks for this. I have a copy of the schematic but I can't identify what capacitor to esr test
 

bertus

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Nov 8, 2019
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Hello,

I tried to download a schematic and got an elbe E19 schematic.
Is this the deflection part of your TV?

Elbe E16 deflection.jpg

If so have a look at Q301,Q302, C307 and C308.
If not, do you have a link to the schematic?

bertus
 

bertus

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Nov 8, 2019
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Hello,

It looks like the vertical deflection is done by a TDA8178S:

E16 deflection.png

There are some scope test images in the schematic.

Bertus
 

bertus

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Nov 8, 2019
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Hello,

What happened in this corner?

E16_20200125_200133_part.jpg

It looks like someone tried to solder something and touched the plastic frame.

Bertus
 

bertus

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Nov 8, 2019
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Hello,

It looks like they tried to solder this region:

E16_20200125_200133_part2.jpg

So to see it is in the audio part.

Bertus
 

Gpit6903

Jan 25, 2020
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Hi,

Yes they have!!!! Why on earth would someone do that. Either way I don't use the audio on the TV as it runs via my amp.

In regards to the vertical deflection, will I need a professional to scope it? Or can I just replace the capacitors?

Many thanks
 

Gpit6903

Jan 25, 2020
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So upon inspection q550 solder was dry with supplies vpos. However upon putting it all back together the linearity is still poor. Any other ideas?
 

Gpit6903

Jan 25, 2020
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Update

After turning the TV on and testing voltages unfortunatly my avo meter grounded 2 pins on the ic. This took out a resistor, I have subsequently replaced the resistor and also 2 capacitors in the vertical ic.

The picture is now a white line which i presume is the Ic tda 8178s burnt out because I grounded it accidently.

1. At least the TV turns back on now after replacing the capacitors (bad values tested with esr meter)

2. I have managed to source a TDA8178S for the mitsubishi deflection circuit.

3. Not sure when it will arrive but is there any other caps I should check to ensure no other problems?

Any advice on the white line would be great!!!!

Thanks
 
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