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February 16, 2008 11:46 AM

Categories: Televisions and Projectors

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Randy

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Joined: 09/09/2005

I've been trying to fix this tv for some time now. I bought the well known PTC replacement and other kits, after replacing all this it keeps blowing fuses. I even checked the net and saw all the postings for this model and the fuse problem. I did what the postings recommended and replaced the original fuse with a slow burn 4A 250v and then a slow burn 5A 250v same problem it blows instantly. I removed the PTC and tried again, same thing. I'm running out of ideas and have never had this much problem with a tv before. Does anyone know what could be wrong with this thing?

Discussion:    Add a Comment | Comments 1-25 of 34 | Latest Comment | 1 2 Next »

February 16, 2008 11:54 AM

if fuse blows right away you have a dead short somewhere. check bridge rect. horz. out trans power supply trans.

February 16, 2008 12:32 PM

Thanks for your help. Yes the fuse does blow instantly and completely blackens.I'll try and locate those components and try testing them. Thanks again

February 17, 2008 8:14 AM

This model was famous for the degauss thermistor drawing too much current at turn on.  The old part, contained in a square white case, gets replaced with a newer thermistor.  Sorry, I don't have the part number. 

February 17, 2008 9:06 AM

Yes I remember this problem too. Unplug the degaussing coil and see if the fuse still blows

"Those who do not know their opponet's arguments, do not completely understand their own".

February 17, 2008 9:37 AM

I have replaced the thermistor with the newer ptc part#212266300019 and fuse still blows. I have removed it completly and tried plugging it in same thing happens. I've replaced the rectifier component 6500, but I hope I put it in correctly. on the board there is a square with a shaded in triangle in one corner does the - symbol of the rectifier go into this side with the +symbol at the opposite end?

February 17, 2008 10:36 AM

Send a picture n what you are talking about please.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 17, 2008 12:31 PM

:

You'll see where the rectifier goes onto the board there is a white border around the four pins with a small white triangle in the right corner, does this signify something on how the rectifier goes onto the board? on the bottom of the board the hole is marked 4 below the side with the triangle I inserted the -pin in this side and + pin at the opposite end. Is this the proper way to insert it? Thanks for your help and hopefully I can get this fuse to stop blowing!!

February 17, 2008 3:55 PM

It is hard to tell. See the +  and the minus on the rectifier? Measure with an ohm meter to the + on that large capacitor right beside it. If the negitive lead to the rectifier is connected to the positive of the cap, it is in wrong. The plus of the cap should connect to the + of the rectifier. Same with the negitive of the recifier should go directly to the negitive of the cap.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 17, 2008 4:14 PM

Thanks for the help, I checked with my continuity setting on my DMM and I have the rectifier in backwards, the + on my rectifier was connected with the - on the capacitor.I'll have to go out tomorrow and get some more fuses then try this out again. Once again thanks for the help!!

February 17, 2008 4:51 PM

I managed to find a fuse amongst all my junk. I flipped the rectifier around put in the fuse and plugged in the set. Well the fuse didn't blow but nothing happens, dead set. Well back to the drawing board but one problem out of the way thanks to you. Thanks again.

February 17, 2008 5:14 PM

Now, double check the capacitor, and make sure you did not blow it out. I myself would replace the capacitor.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 17, 2008 5:36 PM

The capacitor seems fine but I think I'll do like you say and replace it. I'll have to find one next week it's a 470uf 200wv and I doubt I have one here.

February 17, 2008 6:23 PM

I found a capacitor out of another tv that was working, I soldered it in nothing happens. I then checked resistor 3532 and it is also fine, the set will still not turn on.

February 17, 2008 6:47 PM

If you have the schematic or the service manual, send it to techman32k@yahoo.com

"Those who do not know their opponet's arguments, do not completely understand their own".

February 17, 2008 6:56 PM

I checked something I probably should have checked first. I figured seeing the tv won't turn on I'd better check the switch. so I did and there isn't any power anywhere on the board with the on/off switch.

February 17, 2008 6:58 PM

I have the schematic which I bought, but it came in spanish, I'll try sending it to you anyway.

February 18, 2008 7:41 AM

Ok after looking over the schematic, and knowing the bridge rectifier was installed backwards, the first things I would replace would be the power supply regulator IC as well as the power FET. That would be IC7511, and Q7512. I would also check resistor R7.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 18, 2008 9:02 AM

Thanks Larry, I located those parts and I'm going to start with 7512 I'll have to figure out how to test these parts. Once I do I'll get back to you. Thanks

February 23, 2008 7:15 PM

what you need to do is flip bd. over then plug in and measure voltage across cap 2505 thats the cap  in front of the rectifier. it should measure about 160 volts dc. if no voltage there thre should be a low ohm res. in line with ac about a 5 watt res. unplug set and check for continuity.

February 24, 2008 11:43 AM

I checked voltage at cap 2505 and I've got 164 volts. I'm thinking the problem may lie at regulator 7515 but I'm not sure how to check these. I don't have an exact match to substitute and try, but I'm trying to match one up and see if it will work.

February 24, 2008 2:38 PM

There really is no foolproof way of checking that regulator IC, it has to be replace to be sure.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 24, 2008 2:45 PM

I haven't got an exact substite. It's marked B0412 FQPF9N50 can I substiute with an IRF840. They seem to have fairly close specs both being N-channel mosfet.

February 24, 2008 2:47 PM

As long as the specs are the same or exceeds the original, you should be OK.

"Those who do not know their opponet's arguments, do not completely understand their own".

February 25, 2008 12:18 PM

this tv has a switched mode power supply. if you have voltage at the cap you should have it at the regulator.set your meter for setting higher than two hundred volts and see if you have voltage on regulator if you do look at your meter and see if your dot moves back and forth. if it is your supply is up and running. another way to see is check your secondary voltages.if you have b plus (135v) you should also have15v and 30volts for vert.give or take a few volts. if you have no voltage on the seconday side your switched mode supply is not running.our store serviced this brand for many years and i have never ever replaced this part. however if you put br. ret. in wrong it may be bad.

February 26, 2008 8:20 AM

I have voltage between cap and regulator (7512) on drain leg about 171 voltsdc. The dot on my meter doesn't move. When I check for secondary voltage out of transformer 5512 there is none in fact there is no voltage going in. Is this what you mean by checking secondary voltage? 

Discussion:    Add a Comment | Back to Top | Comments 1-25 of 34 | Latest Comment | 1 2 Next »

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