Riddled TV Repair Forum

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

I was watching this CRT TV when all of the sudden the screen was scrambled. I checked to be sure it was the TV, and not the cable system (definitely TV).
View a 20 second YouTube video of the symptom:

http://youtu.be/bHlRCTcHWRo

It has an LA7841 Vertical Deflection Output Circuit on board 4B10B06900.

Is this the problem? Can I test it without a scope? Anybody have a schematic? Any ideas and help greatly appreciated.

Google

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

How do these solder joints look to you (three photos)?

http://www.flickr.com/photos/kfhaggerty/9155805794/

They connect the LA7841 vertical deflection IC to the board. I'm going to clean them up and see if that takes care of the problem.[/img]

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

No effect. (Expletive here), I was so sure. Any help out there?

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Difference manual: http://cmf.fixdevice.ru/smanuals/tv/sanyo/ds27510.html
Service manual: http://elektrotanya.com/sanyo_tv_avm-2751s_g7v-2751s0_sm.pdf/download.html

STAY OUT of the Service Menu in your attempts to solve this problem. IF the WRONG parameter is changed, the TV MAY never work again.

Do the symptoms change if you hook a DVD/DVR to a A/V input? Sound is O.K.? Menus are or are not affected?

I'm not signing up for flickr just to view your pix.

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

The symptoms don't change when switching inputs (DVD for example), and the sound is normal. Resoldering the poor connections to the LA7841 did not fix the problem, so I won't bother trying to figure out a way to attach those photos here. And thanks for the link to that manual.

Google

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Menus (On Screen Displays) are also out of sync? or are they displayed normally?

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

Menus are normal. How interesting. That must mean something important, or you wouldn't have asked, I assume. I never thought to look for that. What do you think? Oh....I have to say thanks again. One couldn't ask for a much better service manual. I wish Polaroid produced something as good, for their flat screens. The manual for the TLA04011C isn't worth a dam n.

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

It just proves that the set is capable of correctly displaying CPU generated graphics.
In your video I note that your screen has a bluish tint, has no horizontal or vertical synchronization and appears a little washed out. I am assuming OSD IS proper - sync is good, as you've already reported, ALSO no bluish tint & not washed out?

The next step I'd take would be to confirm that EEPROM wasn't corrupted by a spike, static discharge or some gremlin passing by.
NOTE: I am just saying to 'confirm' - Check and report - DO NOT ADJUST or change ANY data at this time.

First carefully read pages 4 - 6. I am especially concerned about OPT & OP2 and ANY that are outside the 'Range of Data' (for example, you report a parameter with a data value of say 277 for a parameter that's supposed to have a range of 0 - 31).

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

I'll get to that and have results tomorrow. Thanks.

kfhaggerty · Joined: 27 Jun 2013 Posts: 11

I recorded all of the figures. Here are the two you wanted to see.

OPT 0
OP2 98

I charted all of the readings so if you need others I have them in front of me. The only one I'm uncertain of is #1; Horizontal Frequency. I was going to use my remote control to page up, but inadvertently changed that setting. I'm not sure if it was initially at 29, 30 or 31 when I opened the menu. So I set it at the initial set up figure of 29. I hope that doesn't screw you up any. The TV appears to have no change as a result.