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Sony kv-27fs120 help

 
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wildchild22




Joined: 16 Aug 2008
Posts: 185



PostLink    Posted: Mon Jan 09, 2017 1:41 pm    Post subject: Sony kv-27fs120 help Reply with quote


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I have a sony I got from the scrap yard that shows a pic like this
I am trying to save it but this is its last shot.
I have been troubleshooting and I downloaded the service manual and cannot find anything wrong. So I tried swapping the output at the neckboard green and red channels around by desoldering 1 end of the resistor and adding a jumper. And the pic shows red all the time. So it seems the heater element is shorted in the tube. I read I can run a 22 awg wire from the heater flyback and have a floating ground with 2 wraps and it will fix it. However I am unsure where to wrap the wire. Do anyone have a pic?


So it seems I need to cut pin 7 and 8 from the board.

H1 is heater power pin 7 and pin 8 appears to be ground from the schematic.

So I am guessing after I cut both traces for 7 and 8 I then hook the new wire from the flyback to pin 7 and leave the ground disconnected?




I do see a vertical rod on the transformer with a gap and magnets stacked vertically on the other. Is this where I wrap the wire?

I read about the procedure here but want to ensure I do it correctly.

http://www.tv-forums.com/forum/TV_Equipment_C4/TV_Repair_Forum_F3/sony_27_red_screen_P46608/


Common as Mud for Sony. 9 times out of 10 its the picture tube. It has a heater cathode short on the red gun. All is not lost though there is a modification fix. I had one lady didnt want her TV modified and gave me it. My daughter has had it now for 5 years without an issue. You need to isolate the tube heaters and run them from a 6.3V source easiest is from a wire on the flyback. 2 winds around the cross post will do it, do not fit it around the main body. Glue in place with hotmelt etc, you have to cut the print on the tube base to isolate the low pin from earth, the high pin usually has a resistor, keep that in. Its not an amateur job, I tell you what to do but get a pro to do it or be sure you can solder and understand electronics. Mod is a Sony Australia fix. R


Last edited by wildchild22 on Mon Jan 09, 2017 2:27 pm; edited 4 times in total
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wildchild22




Joined: 16 Aug 2008
Posts: 185



PostLink    Posted: Mon Jan 09, 2017 1:44 pm    Post subject: Reply with quote

Obviously the pic above is before I cut the trace. With the trace cut it does not start up correctly. Just for a sec then blanks.

It is a kv-27fs120 same the post I linked to.
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24006
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Mon Jan 09, 2017 5:19 pm    Post subject: Reply with quote

You need to isolate H1 and H2, then run the wire that you wrapped around the flyback twice to those two points on the CRT\.
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 506



PostLink    Posted: Tue Jan 10, 2017 12:11 am    Post subject: Reply with quote

Could it be that the green gun is experiencing low emission?
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jts1957




Joined: 17 Oct 2016
Posts: 4



PostLink    Posted: Tue Jan 10, 2017 5:18 am    Post subject: Reply with quote

Red gun H-K Short:

Green gun weak:

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wildchild22




Joined: 16 Aug 2008
Posts: 185



PostLink    Posted: Wed Jan 11, 2017 12:48 pm    Post subject: Reply with quote

Thanks Curt

The problem is fixed. After the mod the screen fired right up red as usual for split second then the color changed correct. However I measured the voltage on between the H1 and ground and I am getting 28 VAC is this to much for the heaters?
As they should run on 6.43 Volts DC.
Lastly is the tv still safe modified like this? I cant see why not but do not want to make a fire hazzard.

After a few minutes running it had like fireworks from behind the neckboard with an arcing noise. I unplugged it and waited a bit and plugged it back in. It runs fine now. except every now and then the picture collapses. Like every 15 mins and sometimes it makes like an arc noise. I am hoping it will settle down. If not back to the dump it goes.
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 506



PostLink    Posted: Wed Jan 11, 2017 3:56 pm    Post subject: Reply with quote

You may have some loose filament in there. Try tilting the tv tube face down, and give the neck some good taps (obviously not hard enough to break it). Almost sounds like you did a rejuvenation on it).
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wildchild22




Joined: 16 Aug 2008
Posts: 185



PostLink    Posted: Wed Jan 11, 2017 3:59 pm    Post subject: Reply with quote

Well the screen is starting to turn red again. Not real red but noticable. I do not think this sony is salvagable.
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