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Old 11-07-2012, 04:40 PM   #1
IamCanadian
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Default Toshiba 37AV502R BAD Psu?

Hey Everybody,

Problem:

Starting with the tv unpluged overnight, Plug it in in the morning and it will turn on and work as normal for a few moments, Then restarts, Works for a shorter amount of time, then just goes to a flashing green led.

I took the back off, and Instinctively checked for bad caps/components.

Found 1 suspect Diode with discolored leads from heat, Removed and tested, it was ok. (It was a Avalanche Diode)

The caps look perfect. All caps on the secondary side are marked with KY, I believe they are NIPPON CHEMI.

Even though they look fine I am going to replace them (6 in total)

Does anyone have experience with this brand of cap? is it a known bad company? is it normal for them to fail with no external clues?
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Old 11-07-2012, 04:48 PM   #2
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Default Re: Toshiba 37AV502R BAD Psu?

No need to replace the Nippon Chemicon caps. They are excellent caps. Typically, Toshiba use very good caps. It's typically only premium brands like Samsung and LG which use poor quality capacitors (and other components) and then market their products above others.

Can you post some pictures of the insides of your TV?
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Old 11-07-2012, 05:00 PM   #3
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Default Re: Toshiba 37AV502R BAD Psu?

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Old 11-07-2012, 05:02 PM   #4
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Default Re: Toshiba 37AV502R BAD Psu?

OK, do you have a digital multimeter? (DMM)
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Old 11-07-2012, 05:09 PM   #5
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Default Re: Toshiba 37AV502R BAD Psu?

Here's the SMART guide service material hope it helps in your troubleshooting
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File Type: jpg Snap1.jpg (133.8 KB, 39 views)
Attached Files
File Type: pdf SMART2009-LCD509.pdf (630.6 KB, 73 views)
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Last edited by RON_CET; 11-07-2012 at 06:01 PM.. Reason: additional info service bullentin on power supply
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Old 11-07-2012, 05:10 PM   #6
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Default Re: Toshiba 37AV502R BAD Psu?

I do have a DMM, Any guidance you can give will be greatly appreciated!
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Old 11-07-2012, 05:13 PM   #7
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Default Re: Toshiba 37AV502R BAD Psu?

Quote:
Originally Posted by RON_CET View Post
Here's the SMART guide service material hope it helps in your troubleshooting
Thank you For that!
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Old 11-07-2012, 05:25 PM   #8
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Default Re: Toshiba 37AV502R BAD Psu?

This connector going to the main board needs to be checked with the TV malfunctioning and functioning properly. Are you able to get the TV to turn on at all?

Note: I have no idea of your abilities here, so I'm going to dumb it down a little -- feel free to let me know if you're more confident with meter usage than I'm making out.

Set your meter to DC 20V or if it is an autoranging meter set it to DC volts. Move the red probe into the Volt/Ohm jack and ensure the black probe is in COM.

Place the black probe in the metal chassis of the TV; a screw mount is a good place as the probe will usually sit in there nicely.

Then, touch the red probe on each pin of this connector. You might need to dig it in a little; just make sure you're touching the metal. Record this measurement and report back. Repeat the measurements for the TV working and in standby.
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Old 11-07-2012, 05:28 PM   #9
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Default Re: Toshiba 37AV502R BAD Psu?

I can check while malfunctioning now, to test while working I will have to wait 4 hrs for the fault code to reset. I am competent with the use and terms of a DMM. No need to dumb it down.
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Old 11-07-2012, 05:31 PM   #10
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Default Re: Toshiba 37AV502R BAD Psu?

Malfunctioning will be fine for now, I will check in the morning if you have the other readings. If the power supply is outputting the right voltages while TV is malfunctioning, it usually indicates a main board fault.
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Old 11-07-2012, 05:39 PM   #11
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Default Re: Toshiba 37AV502R BAD Psu?

Yeah I figure that too, Still not 100% sure about the brand of the caps.
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Old 11-07-2012, 05:42 PM   #12
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Default Re: Toshiba 37AV502R BAD Psu?

Quote:
Originally Posted by IamCanadian View Post
Yeah I figure that too, Still not 100% sure about the brand of the caps.
Little "crown" symbol on them, brown colour, KY series? Like this?
http://ecx.images-amazon.com/images/...500_AA300_.jpg

Nippon or United Chemicon. They are in the big 4 of cap makers: Nichicon, Panasonic, Rubycon also join them. They are regarded as being very good, I have only ever seen one go bad on a motherboard, and it was very badly bulged. Apparently that's the one place they don't survive well.
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Old 11-07-2012, 05:46 PM   #13
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Default Re: Toshiba 37AV502R BAD Psu?

Ok yup that is them. Thanks I will post up results tomorrow of at fault and working tests.
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Old 11-08-2012, 12:12 PM   #14
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Default Re: Toshiba 37AV502R BAD Psu?

While tv is working all voltages are right 5v, 12v and 24v, BL on is only 4.25v
Dim is 3v. secondary transistors heat up very fast though.

When not working 5v pins 11 and 12 (pin 10 is nc) fluctuate from 1-2v, But show 5v with cable to main board disconnected. pin13-16 fluctuate as well
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Old 11-08-2012, 12:16 PM   #15
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Default Re: Toshiba 37AV502R BAD Psu?

Do you have a hairdryer or hot air gun (max about 60C) you can easily use? Heat up this portion of the board while it's flashing away and see if it starts up. In particular, that small capacitor in the middle can fail causing the 5V output to pulse with high load (like a main board.)

If it does start, turn it off, wait for it to error out, then repeat the test. If it starts again, you should suspect that capacitor.
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Old 11-08-2012, 12:18 PM   #16
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Default Re: Toshiba 37AV502R BAD Psu?

lol I have a hot air gun right beside me, I will give it a go, stay tuned, and thank you for your lighting fast reply's
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Old 11-08-2012, 12:23 PM   #17
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Default Re: Toshiba 37AV502R BAD Psu?

Heating up that part of the power supply did put the voltage back to a solid 5v but still pulsing.
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Old 11-08-2012, 12:24 PM   #18
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Default Re: Toshiba 37AV502R BAD Psu?

the tv just came back to life by itself just after my last post, it has never done that before without being unpluged for 4 hrs
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Old 11-08-2012, 12:41 PM   #19
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Default Re: Toshiba 37AV502R BAD Psu?

So it would seem like heating that cap has had an effect? Can you repeat it? (Note -- it might take some time for the heat to reach the cap, so try circling right around it if you can.)
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Old 11-08-2012, 12:46 PM   #20
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Default Re: Toshiba 37AV502R BAD Psu?

ok each time i apply heat to that cap tv works well, i will proceed to replace it
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