Riddled TV Repair Forum

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

Hi Guys,

I had a convergence problem on this set and decided to replace the convergence IC's. The TV worked (although in a 3D way) prior to my swapping out the IC's. I am a service technician and have fair soldering skills, but be that as it may, I still have a TV that upon power up does nothing. There is no display or audio. There are five green LED's illuminated and not flashing- I believe the power is good. There is also a Red LED labeled "protect" that may be pointing me in a direction, but I do not know where.

Can someone assist me with troubleshooting this?

Much thanks!

Google

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

Upon further investigation, I found fuse F906 blown. It is a 1.6a fuse. I replaced the fuse and upon power up, it immediatly blew again.

Any suggestions?

Thanks,
John

kuhurdler · Joined: 28 Dec 2006 Posts: 2580 Location: Overland Park, KS

check your solder splashes around the ICs. If it was working before, something you did had to have changed that.

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

I've checked and found a short between pins 8 and 9 on IC K05. i unsoldered the pins and the chip is not shorted, it is the socket points that are shorted. I am getting ready to dig deeper, but could sure use some guidance...

Thanks!

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

Well, after pulling up the prints, it appears pin 8 and 9 should be shorted, they are both +26V...

Back to the drawing board...

On another topic, how do you upload an image/picture?

Thanks

Google

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

I've removed the convergience chips from the board and the fuse is still blowing. IF906 is for the 110B+...

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

F906 is in the 115V supply.
Check the Horizontal output transistor Q777
Solder the driver transformer T701 if Q777 is shorted. Then replace transistor.

Hope this helps

Jesse

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

Thanks for the suggestion Jesse. I have been swamped this month and have not gotten back to the TV. Hopefully this weekend. I'll update if I make any progress.

Thanks for the suggestions!

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

Q777 has a generic number of 2SC4589-05 and a hitachi number of 2315274F and is available here: http://www.andrewselectronics.com for $11.61

The Emitter and Base of this transistor is directly across the driver transformer and will always read low in-circuit. The transistor should read like a diode between the Base and Collector and most of the time will read open between the Collector and Emitter. The Emitter and Base are the legs that are the furtherest apart on the transistor itself. The Collector is the center leg.

T701 is a small driver transformer that is surrounded on three sides by the same heatsink that Q777 is mounted on. Be sure to solder all of the legs of this transformer. Usually this transformer has cracked joints that distort the waveform causing the horizontal output transistor to fail.

Hope this helps

Jesse

Bigfoot · Joined: 09 Jan 2009 Posts: 7 Location: St. Louis

This did help a lot! The transistor was toast, so I got a "suitable sub" form Radio Shack because I was impatient. The suitable sub worked for about 6 hours then shorted out as well. My plan is to order an original and resolder the legs of the transformer (on my initial inspection, I thought they looked okay- this time I will make sure).

Thanks!

One item of note is that when the set was functioning properly, the red "protect" LED was still illuminated...