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?
if fuse blows right away you have a dead short somewhere. check bridge rect. horz. out trans power supply trans.
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
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.
Yes I remember this problem too. Unplug the degaussing coil and see if the fuse still blows
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?
Send a picture n what you are talking about please.
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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!!
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.
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!!
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.
Now, double check the capacitor, and make sure you did not blow it out. I myself would replace the capacitor.
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.
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.
If you have the schematic or the service manual, send it to [email protected]
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.
I have the schematic which I bought, but it came in spanish, I'll try sending it to you anyway.
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.
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
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.
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.
There really is no foolproof way of checking that regulator IC, it has to be replace to be sure.
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.
As long as the specs are the same or exceeds the original, you should be OK.
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.
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?
yes. if you have voltage on regulator you have to have it on one pin of the transfomer. the primary side.however if you check on the secondary side of transformer and you have no dc voltages then your power supply is not runnng. switched mode supplys are not easy to troubleshoot.you can start by replacing regulator but also check bias resistors all around the regulator. if you follow the lead on reg. that has 171v on it that trace should go to a pin on the primary side of trasformer that voltage must be present and it has to be switching. thats what i ment when i said the dot will go back and forth.also this supply has an isolated ground on the primary side. so make sure you take a good ground on the primary side.if you measure on the secondary side you must change your ground lead on that side of transformer.
I checked the primary side there is 171v going to pins 2 and 3 of the transformer from the gain on the regulator however it is not switching, the dot does not move. As for the secondary side there is no voltage at all.
if you have no voltage on secondary side of transformer your supply is not running.im assuming you moved your ground when you checked b plus on secondary side.primary and secondary are two differnt grounds.with set off you should measure 130 or so volts at horz. output transistor.dont measure this when set is running.if no voltage present somthing in reg. circuit is not right these are not easy to troubleshoot.
I finally have power on this thing. The green led on the front is finally lit and the fuse does not blow anymore. Now my only problem is that the set won't turn on when you hit the power button!! Any suggestions?
I measured for power. I was told by another member to watch my meter for switching power. I measured at component 7512 for switching power and there is none. Hopefully I'm doing this right (I'm a rookie) I got the tv out of the garbage for something to learn on it was completely dead and now I have stand by power.
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