I am an electronics newbie and have what appears to be a fairly simple repair to do on my T.V. I have heard from another forum that this problem is fairly common on my model of T.V.
The problem is that when I turn the set on, all I get is bright white horizontal lines across the screen--then the set turns itself off after 5 seconds. I have been told that the problem is the 10 ohm # 3340 resistor is burnt open. This resistor is on the crt board and easily accesible.
My first question is: Should the resistor show visible damage or could the damage be internal only? Upon visual inspection I see no signs of overheating.
The second question is: Do I need to bleed off any residual or stored electricity before replacing the resistor and if so how?
Thanks in advance for any help you are able to give and have a safe 2004.
T.S.

 

hi,

a resistor may show a very visible damage sign, others may not. but the best way is to check it with a tester. if you have infinite reading its open.

but there might be other causes to your problem :cry:

__________________
\"NONE BUT THE BRAVE DESERVES THE FAIR\" ~Shakespeare~

 

Hello and thanks--I miss my tv!
As for testing--would I use just an ampmeter or should I get a special tester for this? Also--can I safely test without bleeding off the electricity first?I know that I sound ignorant about this stuff--because I am--but aside from the cost savings I enjoy being able to repair things myself--I guess it gives me a sense of accomplishment.
Once again thanks.T.S.

 

What you are describing is called vertical field collapse. I means that the vertical deflection coil is not being properly driven. If you suspect the resistor, just unsolder one end, and then use an Ohmmeter to measure its value. Some TV's have a small value, fairly high wattage, resistor in series with the vertical deflection coil to reduce ringing.

Also, before working on the TV, unplug it completely (do not use the on/off switch for this purpose). Then get a very well insulated flat blade screwdriver (thick undamaged plastic handle). Get a piece of wire with alligator clips on each end. Clip the shaft of the screwdriver, and clip the metal part of the chassis with the other end. Now gently insert the blade under the anode cap (kind of like a suction cup) which in on the tube. Hold the screwdriver on the handle only. You should hear a big clap when you finally touch the anode hook. It may startle you if you are not accustomed to this.

Finally, if you have any reservation whatsoever, please do not attempt this!

 

No it's not!, he mentioned 'lines' not 'line', it sounds like the HT feed (200V or so) to the video output transistors is O/C - this gives a bright screen with even brighter flyback lines across it.

However, it's unlikely to have gone without any reason - but seeing as he hasn't mentioned the manufacturer (never mind the model number as well), there's not a lot I can really suggest.

A common fault on various Grundig sets is the video output I/C going S/C, this is usually caused by the CRT flashing over internally.

 

Good morning and thanks to all. Sorryabout not mentioning the brand--it is a Phillips Magnavox model TP2785C221. The lines do cover the entire screen from top to bottom. Have a great day.
T.S.

 

An open R3340 is a known problem that will cause a bright screen with retrace lines followed by set shutdown on that model...

 

When doing this on a older sony tv (trinitron models with only 1 electron-cannon (or whatever the english word for it is)) be aware that they have a spring underneath the cap. lifting the cap to much without special equipment will make the spring drop inside the tube, wich means the end for it.

got nothing to do with the philips tv in this thread but just mentioning it

 

Just for the record, I retract my diagnosis given earlier about vertical field collapse. I misread the lines vs. line, as Nigel pointed out.

Also, I am not familiar with Grundig TV's, or any TV's, European or otherwise, for that matter. I used to work on the small signal design of RGB monitors, two jobs ago.

Jem

 

A big thank you to all who offered help and advice to this clueless newbie. I am very grateful for you who shared your knowledge with me.The repair went off without a problem and thanks to the advice that I received I felt confident from beginning to end. The set is back up and rotting my brain, good as new.


Thanks and God Bless.
T.S.