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Old 07-16-2019, 01:49 AM   #1
beetle1303
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Default Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Hi,
I'm a newbie wanting to learn by doing (with rubber gloves and rubber shoes on).

This is what I have:
TV: Toshiba 32AV600E (230V)
PS model : SRV2169WW-I - 68-FB43B (see Pic01, Pic02)
Main Board : PE0736

1) Plugged TV into wall power supply - no Red standby light. Pressed power button, nothing happened.

2) Opened up TV, checked fuse blown, and replaced it.

3) Now Red standby light turned on for 5-6 seconds, then went off. Pressed power button, nothing happened. Power off/on, no Red standby light either. But unplugged from wall socket for few minutes, plugged in again, the cycle repeats.

4) Did some poking around the PS with DMM, found 240Vac and 320Vdc at the primary side, and 5Vdc at 5V1 pin (see Pic03, presumed to be Standby)

5) Removed the PS board, found 2 burnt marks on the plastic sheet backing the PS (see Pic04)

6) Checked the corresponding spots on the back of PS, using DMM to test the resistors, found R834 and R835 Opened, and the other 2 beside it are OK (see Pic05, Pic06)

*Some Pics are courtesy of forum member @Carbonfiber in a similar tread here.

I have and can handle some simple soldering/de-soldering of larger components like big capacitors, but I do not have tools and parts to replace these 2 resistors.

At this point, I am seeking help to determine if these 2 burnt resistors is the root cause of this TV not powering up issue before further debugging.

Any advice is appreciated.

Thank you.
Attached Images
File Type: jpg Pic01.JPG (239.0 KB, 12 views)
File Type: jpg Pic02.JPG (960.3 KB, 9 views)
File Type: jpg Pic03.jpg (308.3 KB, 8 views)
File Type: jpg Pic04.jpg (259.2 KB, 8 views)
File Type: jpg Pic05.JPG (25.4 KB, 14 views)
File Type: jpg Pic06.jpg (280.2 KB, 13 views)
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Old 07-16-2019, 02:25 AM   #2
yokoono
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Unfortunately for you the repair is quite complicated for a beginner (controller, mosfet etc.). And the harder a forum. Call a more knowledgeable electronist and watch him fix it. An electrical fuse burns out of a cause. Simply replacing it does not solve the problem. Especially since, from the pictures, it is seen that the source is quite burnt.
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Old 07-16-2019, 02:35 AM   #3
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

For my education, would restoring these 2 burnt resistors be the first step to get started with the debug/repair process?
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Old 07-16-2019, 02:50 AM   #4
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

NOT. The first step is to find out WHY THE RESISTANCE HAS BEEN. The cause must first be sought and then the defect removed. If you replace only the resistances will burn again.
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Old 07-16-2019, 03:28 AM   #5
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

To trace forwards/backwards to/from these resistors in the circuitry is definitely beyond me... However, if they were caused by external factors like lightning power surged that blown the fuse and these resistors, then restoring them could yield a positive outcome?
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Old 07-16-2019, 03:43 AM   #6
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

A flash on the power supply almost irreparably destroys the power supply. A lightning strike on the signal path irreparably destroys the motherboard.
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Old 07-16-2019, 09:02 AM   #7
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Check and see if this is a match, don't know anything about the seller, just ran across the ad, they do have 100 percent feedback: https://www.ebay.com/itm/srv2169ww-p...EAAOSwQ7lcs4GQ
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Old 07-16-2019, 03:41 PM   #8
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

The two burnt resistors are 33Ω according to picture 6
I suspect Q801 & Q802 are shorted and likely other components like Q803 & Q804, R819, R808 and possibly IC801
It is likely Q801/802 shorted drain to gate and burnt the two 33Ω resistors, If that IS the case, there was +300 volts on those two resistors/q803/804 and the ic which can not handle more than 10~20 volts max

Last edited by R_J; 07-16-2019 at 03:57 PM..
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Old 07-17-2019, 07:58 AM   #9
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

nomoresonys: total costs is rather high and could buy a similar functional resale unit here in Singapore, but thank you.

R_J: I will take out the board and measure these components to see what I get, and report back later. Thank you.
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Old 07-17-2019, 09:25 AM   #10
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

So I did some in-circuit measurement using my DMM:
1) Q801, Q802, R808 are shorted
2) R819 is good
3) Q803 & Q804 - pardon me I do not know what these are, and how to measure them. I put my DMM into continuity mode, black lead on right side and red lead on each of the 3 resisters. The outcomes are 764, 1, 764 to R833, R834, R835 respectively (see attached pic)
4) I do not know how to check IC801...

In trying to replace those opened / shorted resistors, can I use the traditional resistors in place of those smd type?
**I don't have proper tools and skills to fix those tiny resistors...
Attached Images
File Type: jpg Pic07.jpg (377.1 KB, 6 views)

Last edited by beetle1303; 07-17-2019 at 09:29 AM..
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Old 07-17-2019, 09:53 AM   #11
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Quote:
Originally Posted by beetle1303 View Post
nomoresonys: total costs is rather high and could buy a similar functional resale unit here in Singapore, but thank you.

R_J: I will take out the board and measure these components to see what I get, and report back later. Thank you.
I hear you, I wouldn't put more than a few bucks into a 32 inch screen.
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Old 07-18-2019, 09:00 AM   #12
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Quote:
Originally Posted by nomoresonys View Post
I hear you, I wouldn't put more than a few bucks into a 32 inch screen.
Me too.. the (learning) journey is more important than the destination (a working TV)
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Old 07-18-2019, 01:12 PM   #13
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Q803 & Q804 are transistors, You would need to look at the marking code on them (it's small) to know what they are. This could be the pinout.
The ic can't really be tested, you would need a scope to look at its output to know if it was working and outputing the drive signal
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File Type: jpg NPN2_-W600.jpg (17.4 KB, 5 views)
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Old 07-19-2019, 12:04 AM   #14
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

Thank you R_J, I took a close-up pic of Q803 & Q804, and googled for a closes match (see pics)

Since I have no ways to test them, I will leave them to last. For a start, I will source replacement parts for Q801, Q802, R808, R834 & R835, solder them on and see what will happen.
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File Type: jpg TransistorMyBoard.jpg (224.5 KB, 4 views)
File Type: jpg TransistorWebsite.JPG (19.4 KB, 5 views)
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Old 07-19-2019, 09:11 PM   #15
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

If you found the picture, what is the transistors number? is it 2SA1576A-Q ?
How did you test Q801 & Q802? Q803 & Q804 are likey just transistors, use your meter in diode test. Google " how to check a transistor with a meter"
And you can't just replace Q801,802 and the resistors, without having the drive signal from the ic, the parts will likely just blow up again.
Another example would be if the ic's output is shorted high. that would fully turn on Q801,Q802 and they would likely short instantly.

Last edited by R_J; 07-19-2019 at 09:43 PM..
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Old 07-20-2019, 03:47 AM   #16
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

https://www.youtube.com/watch?v=KGcoOETCaEQ
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Old 07-20-2019, 08:30 AM   #17
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

These are the names associated with the pic I found - 2SA1037AK / 2SA1576A / 2SA1774 / 2SA2029 / 2SA933AS (see attached datasheet)

I did google and follow those videos on how to test a mosfet transistor using DMM - on Q801 & Q802, all permutations of black and red leads on any of the 3 pins will "beep", compare the Q881 & Q882 which will not beep whichever ways I touch the leads.

On Q803 & Q804 are also never beep whichever ways I touch the pins.

On IC801 - can't see the marking on this chip, any way to find out?

So I guess I should also check on IC801 and replace it as the same time if this chip is bad.
Attached Images
File Type: jpg Q801-Q802.jpg (247.9 KB, 3 views)
File Type: jpg IC801-Corrected.jpg (363.6 KB, 2 views)
Attached Files
File Type: pdf datasheet.pdf (78.8 KB, 5 views)

Last edited by beetle1303; 07-20-2019 at 09:49 AM..
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Old 07-20-2019, 11:25 AM   #18
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

DO not rely on That @%$%^BEEP, it is meaningless, (most meters will beep between 0 and 150Ω) to check the transistors use diode test an your meter, place one probe on the base an then the other on collector, then emitter, it should read aqround .6xx ~ .7xx. Its similar to checking a diode. If you do not get a reading, reverse the probes. The check between collector and emitter, this should check OL or open.
If you are not getting a reading, the transistors are likely blown open, just like the resistors. You can clean the ic with alcohol and you should be able to read the number, It could be a NCP1207A

Last edited by R_J; 07-20-2019 at 11:31 AM..
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Old 07-21-2019, 08:55 AM   #19
beetle1303
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

OK, here's an update to measurement readings:
- Q881 & Q882 has the marking as Q801 & Q802. I put the red probe at the right pin, and black probe at middle pin read 576, and left pin read 864, both Q881 & Q882 are about the same.
- I repeated the same on Q801 & Q802 - both read 002 (and beep) middle and left pins.
- on Q803 & Q804, I am assuming pin 2 is Base, and pin 1 is Emitter, pin 3 Collector. Red probe on pin2, black probe on pin 3 read 763, on pin 1 read 1 (open?). Reversig the probes gave the same readings. Both Q803 and Q804 gave same readings.

I don't have alcohol to clean the IC, and the best pic I can get read something like ??501 (see pic)
Attached Images
File Type: jpg IC801.jpg (259.6 KB, 8 views)
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Old 07-21-2019, 01:49 PM   #20
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Default Re: Toshiba 32AV600E - Standby lights goes off after few seconds, cannot power up

"- on Q803 & Q804, I am assuming pin 2 is Base, and pin 1 is Emitter, pin 3 Collector"
You cannot assume the pin out of the device, you need to look up the spec sheet to get the pin out.
Example: look at post 13.
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