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Philips 32PT5441 & Magnavox 25TS52    
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jmricker



Joined: 30 Jun 2009
Posts: 6
Location: North Carolina

PostPosted: Tue Jun 30, 2009 6:19 pm    Post subject: Philips 32PT5441 & Magnavox 25TS52 Reply with quote

I've acquired two televisions and had a few questions about how to go about fixing them.

Recently my in-laws TV (Philips 32PT5771) went out on them and I said I would try my hand at fixing it. I've wanted to learn more about electronics and electronics repair so this seemed like a good opportunity to get started. Also, I rescued a TV (Magnavox 25TS52) off of freecycle that the person giving it away said needed to have the on/off switch repaired. Of course its not that easy Smile My wife says I'm started a hospital for electronics but this may be hospice care at best.

The Philips powers up, gives three lines, one red, one green and one blue for a few seconds then it shuts off. Is this horizontal deflection?

I also have some questions about dealing with the electricity. If I've discharged the CRT, does that take care of all the dangerous electricity? Or am I supposed to discharge the individual capacitors as well?

I'm also waiting on a voltmeter that I've ordered so I have only done a visual inspection of the two board. The Philips has one resistor that has a red smear underneath it. That isn't a burned place is it? I'll know more when I can test it.

Finally the Magnavox doesn't power up at all and the fuse looks to be in good shape. Where should be the next direction in troubleshooting?

Thanks
Joel
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JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Tue Jun 30, 2009 7:01 pm    Post subject: Reply with quote

You may want a thread for each of these sets.
If Philips "Lines" are horizontal ACROSS the center of the screen, is Vertical deflection thats defective.

Some electrolytics will still contain a charge when the set is unplugged. The charge will bleed off most within 20 - 30 seconds. But shouldn't hurt anything to discharge with a couple K ohm 10 watt resistor if it makes you feel better.

Good magnifier is helpful for visual inspections.

Magnavox: start with the Switched Mode Power Supply secondary. Are there voltages (Ground Reference: Tuner shield) on the non-transformer-connected side of the diodes (usually the line or Cathode)? If not move back to the primary (Ground Reference: Main lytic or bridge rectifier "-")
and see if regulator is getting b-plus. If NO secondary voltages and regulator has b-plus ... most likely regulator is defective.
jmricker



Joined: 30 Jun 2009
Posts: 6
Location: North Carolina

PostPosted: Wed Jul 01, 2009 5:12 am    Post subject: Reply with quote

Thanks, this gives me something to chew on while I wait for my voltmeter to arrive.

JTS1957 wrote:
You may want a thread for each of these sets.


Ok, I'll probably focus on the Philips first anyway so I'll start a new one for the Magnavox later.

Quote:

Some electrolytics will still contain a charge when the set is unplugged. The charge will bleed off most within 20 - 30 seconds. But shouldn't hurt anything to discharge with a couple K ohm 10 watt resistor if it makes you feel better.


How much juice are we talking about anyway? I've been reading conflicting reports about working with televisions. One site will say something like you will die from monkeying around with a television and others will say pfft, nothing harmful at all. What do you say?

Quote:

Good magnifier is helpful for visual inspections.


I can see that already plus a good light. I'll post pictures later about what I find if anything.

Thanks
Joel
JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Wed Jul 01, 2009 8:02 am    Post subject: Reply with quote

How much juice depends on the circuit that the cap is in.
The most dangerous area in any TV is the LOW voltage power supply (remember the input for this is 120VAC, just like the wall outlet), you're talking up to a few hundred volts at currents well over lethal levels. That's with the unit working normally.
Some believe the HIGH voltage area is more dangerous. My opinion: hogwash. The voltages are up to 40KV but the current is so much less. It will get your attention if you accidently connect to it, but you are more likely to be hurt by your "reaction" to it than the shock itself.
Now having said that, unless you are a total klutz (I'm not), or have heart problems (I Do), if you observe the proper care, you should be safe enough. You may have read that you should keep one hand in your pocket - good advice.
jmricker



Joined: 30 Jun 2009
Posts: 6
Location: North Carolina

PostPosted: Sun Jul 12, 2009 6:07 pm    Post subject: Reply with quote

A little bit of a delay from my last post. The multimeter I ordered evidently came on the slow boat from China and I needed to gather a few other tools I didn't have like a good soldering iron and whatnot.

JTS1957 wrote:
You may want a thread for each of these sets.
If Philips "Lines" are horizontal ACROSS the center of the screen, is Vertical deflection thats defective.


They weren't exactly in the center of the screen. I would say the lines were in the center of the bottom half of the screen going across and each spaced about a half inch apart. Does that make a difference?

I don't see anything that jumps out at me as being the vertical deflection ic but I'm going to try resoldering all of them thats attached to a heatsink. Can't hurt right? Several of them are covered by the heat sink so its hard to read any identifying numbers on them. Also there is some dark gunk on some of the connections -- is a sign of bad connections as well?

Thanks
Joel
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JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Sun Jul 12, 2009 6:52 pm    Post subject: Reply with quote

Lines similar to this?
http://www.riddledtv.com/repair/journal/Vertical/horizontal_line.jpg
Just did Google on Philips model number - only two results - both refer to this thread? Partial Mag # = many hits. Also what type of display, CRT/LCD, etc.?
jmricker



Joined: 30 Jun 2009
Posts: 6
Location: North Carolina

PostPosted: Mon Jul 13, 2009 1:36 pm    Post subject: Reply with quote

JTS1957 wrote:
Lines similar to this?
http://www.riddledtv.com/repair/journal/Vertical/horizontal_line.jpg


It doesn't quite look like the same. Here is a picture of what I see:



Hope thats clear enough to see. The lines aren't bunched up like the one you showed but spaced a half inch apart.

JTS1957 wrote:

Just did Google on Philips model number - only two results - both refer to this thread? Partial Mag # = many hits. Also what type of display, CRT/LCD, etc.?


Opps.. wrote down the wrong number. Its 32PT5441 and its a CRT display.

I also have two pictures of the board I thought I would share.



JTS1957



Joined: 21 Jan 2009
Posts: 2395
Location: Far, Far Away

PostPosted: Mon Jul 13, 2009 2:42 pm    Post subject: Reply with quote

So much easier with pix...

Found these:
This one had 3 color lines at the 1/3 bottom of screen the two smd caps 2456 / 2490 were burnt on the board,
cap 2465 was leaky and smd diode 6457 was shorted.

Turns on with 3 colored lines 3/4 way down screen audio then shutdown. replace d 6457 ans cap 2465.

Value Of 3371 Resistor On Crt Pcb After 6457 Replaced, 470 ohm 1/4 watt



This is also one of the sets that has degaussing thermistor/blows fuse. And H. Driver upgrade kit.
jmricker



Joined: 30 Jun 2009
Posts: 6
Location: North Carolina

PostPosted: Tue Jul 14, 2009 4:34 pm    Post subject: Reply with quote

Oh thats great information. I also found a schematic online to help identify the diode. Now that I've finally found it, I found a place to order and just have to wait until it arrives. For anybody else with this problem, here is a pic of the location and a closeup of the schematic:





I'll post more when I receive my shipment.
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