CRT TV Mitsubishi CT29AS1 Vertical deflection problem?

[Gpit6903]

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]

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?

 

[bertus]

Hello,

The following page will tell you a lot of repairing a TV:
http://www.repairfaq.org/sam/tvfaq.htm

For vertical problems have a look at this part of the page:
http://www.repairfaq.org/sam/tvfaq.htm#tvtvnonl

Bertus

 

[Gpit6903]

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

 

[bertus]

Hello,

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



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

bertus

 

[Gpit6903]

Hi Bertus

I have this the exact schematic for my model.

https://drive.google.com/file/d/17G4UVAZuo9TQBnIG0Kg4wfGKtOe8NYdO/view?usp=drivesdk

Hopefully that works, it's the E16 complete Chasis.

Let me know really do appreciate your help, I will post pics if that helps

 

[bertus]

Hello,

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



There are some scope test images in the schematic.

Bertus

 

[Gpit6903]

I think I have the deflection circuit here

https://drive.google.com/file/d/17UhppMuCPGWUx9cbFlsctWWDNJIqLaSg/view?usp=drivesdk

Some of the solder looks in a bad way, what's happened?

 

[Gpit6903]

Hmmm

So does that mean its not a simple capacitor esr test and change?

https://drive.google.com/file/d/17q4xoHQP2K9jLWsg_IbBidEvXI3lUPms/view?usp=drivesdk

Here's a pic from above in the board itself

 

[bertus]

Hello,

What happened in this corner?



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

Bertus

 

[Gpit6903]

Woah, so has it been repaired before?

 

[bertus]

Hello,

It looks like they tried to solder this region:



So to see it is in the audio part.

Bertus

 

[Gpit6903]

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]

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]

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

 

[Gpit6903]

Advice anyone?

I'm about to start replacing the ic today.