Sony KDL-46VE5 - no power, no standby or LED

[gintama]

This time around, I'm hoping I can save some friends from having to buy a new set. Their TV is the Sony Bravia KDL-46VE5 [mfr link] - one day it just wouldn't turn on, and no LEDs were lit. There was no known physical trauma or input power issue.

I've opened it up and blown the dust off, and done some minor poking around with a DMM... The only thing I've really determined is that there's no standby power / no voltages going to the main board. The main fuse is good, the power button and phantom-drain/eco-switch are also fine, and none of the (mostly Rubycon) caps are bulging. I'm guessing this points to a power supply issue.

As such, here are some photos of the power PCB, part 8-597-105-11 / board 1-878-773-23:



The main PCB on this one is board A-1641-795-A or 1-879-239-13 (shopjimmy lists the latter number as 1-879-239-12, but the other one matches). Didn't have a chance to remove this board or take photos.

I'd really appreciate if anyone is able to help out - and let me know if more or better photos are needed.

[gintama]

I can't edit the first post any more, but I forgot to mention I'm looking to repair the problem board rather than replace it. It's a 2009 set and boards are scarce/expensive.

Additional photos - the main board and overall layout.

[CapLeaker]

Since you got no 3.3V STBY voltage, do you have 170V DC on the main filter caps?

First picture top right, there is a silver heat sink. On the left of the heatsink there is a small transformer and a small IC. That is the stby section in the primary. I think the IC is IC6200. What is printed on that IC?

[R_J]

I believe the standby (primary) circuit is what I outlined in yellow, check the number on the ic to get what the voltages should be, also check the resistors (in red) R6016 (does go open sometimes) and check R6200 & R6202, I think they supply voltage for the standby ic.
If measuring voltage you should have around +160 accross C6503 or C6501, If you have that voltage (negative probe to - of c6503) you should have close to the same voltage at R6200 and then at R6202 and then at pin 5 of ic6200

[gintama]

IC6200 is a Panasonic MIP2H2. The datasheets all seem to be for complete power supply circuits, but I found a document on Scribd titled "Sony Training Manual Chassis WAX2T" which shows the following table:

Pin | Function | vDC  | vAC/Hz
1     VDD        6V
2     FB         1.8V
3     OLP        0V
4     VCC        13V
5     DRAIN      390V   ~500p-p ( 45kHz )
7-8   SOURCE     GND

"This circuit develops two voltages, 3.3v STBY voltage for devices such as main uPC, EMMA processor, IR receiver; and 17.5v for main converter (controlled by Power On line)".

The two axial resistors (R6500/.47Ohm and R6200/10Ohm) are within parameters.

This rectangular one next to the relay (R6016/6.8Ohms) reads ~35MOhm or nothing at all, which I take it means it has failed open.


I didn't get to any powered tests tonight. Are the previously suggested ones still needed? If so I'll get to them in the morning.

[budm]

Start checking for shorted parts in the primary side.
That resistor/thermal fuse is for inrush current limiter, it is bypassed when relay RY6000 is turned on, if the relay contacts are bad then that resistor will not be bypassed so it will burn open circuit when TV is trying to pull full current.
So look for shorts first, then the relay contacts (more difficult to check).
Since that resistor is open so you will not have AC feeding the bridge rectifier.

[CapLeaker]

it does happen that just the "inrush current limit resistor" fails (but then you would have to look hard at the relay). But I would definitely check if there isn't a short in the primary or the fact of a bad relay as budm suggested.

[ernest79336]

I have the exact set same problem i took the cover off the relay and it will turn on if i manually push down on the relay to make it connect so is it bad?

[dick_barton]

Have you checked the resistors identified above?

[gintama]

I replaced the fusible resistor (R6016) on mine but there was no change. I couldn't find a suitable replacement for the relay in my parts bins so that's as much as I've had time for so far.

ernest79336, can you show a picture of the uncovered relay? I didn't realize you could do that without destroying them or I would have tried it!

[gintama]

Oh my. That was... embarrassingly simple. After ernest's post above, I took a closer look at the relay, to find that there's a clearly visible line where the housing goes on, and even large clips showing it's intended to be removed. I gently pressed on the side of the housing to see how loose it was - and it just popped off. I had no idea they weren't sealed units.

So I verified all the connections were in order, applied power, and manually closed the relay... After hitting the power button, the set lit up fine. Plugged in a old game system, audio and video seem normal.

Not sure what to do now. As I understand it, this narrows down the problem to the stand-by circuit. That relay connects the 120V lines, so as a last resort I could rewire the "Power Saving" switch on the TV to manually bridge that connection (instead of breaking the 120V circuit before the power supply like it does now). I'd prefer to fix it properly though...

[gintama]

Taking some measurements, finally.

Originally Posted by R_J

I believe the standby (primary) circuit is what I outlined in yellow, check the number on the ic to get what the voltages should be, also check the resistors (in red) R6016 (does go open sometimes) and check R6200 & R6202, I think they supply voltage for the standby ic.
If measuring voltage you should have around +160 accross C6503 or C6501, If you have that voltage (negative probe to - of c6503) you should have close to the same voltage at R6200 and then at R6202 and then at pin 5 of ic6200

No voltage across the two large caps (C6503/C6501), or the nearby resistors (R6200/R6202), same at IC6200 pin 5. R6202 has a resistance of about 36 kOhm, but I'm not sure what it should be - the only legible markings say 1 Watt and 104 J.

With the TV plugged in (but the relay not closed), IC6200 reads 1.15VDC at pin 1, and 0.24VDC at pin 4. With the relay closed, these read 6VDC and 11VDC respectively, which are near spec.

[dskall]

I had same problem cleaned the contacts on the relay with a business card and still working.

[gintama]

Thanks for the suggestion, but with no power to activate the relay, I doubt the condition of the contacts is much of an issue.

[gintama]

Well, this project sat on the workbench long enough, here is the final outcome.

I found multiple places that still had stock of the needed power PCB, most at a cost of USD ~$100 with shipping to Canada. Most had exactly the same quantity available, so were probably just storefronts with the same supplier. My friend wasn't sold on putting that much money into an old TV and possibly still ending up with it not working, so I proceeded with my earlier plan.



The lower trace to CN6003 (the Energy Saving Switch) was severed, and a jumper was added to connect that point to one of the relay contacts (RY6000, just above the "R"). The upper point of CN6003 is already connected to the other relay contact. Finally, a jumper was connected between the two nearby test points, JL6523 & JL6524 to replace the switch.

When the Energy Saving Switch is ON, the TV's standby LED comes on and the unit behaves as expected. When the switch is OFF, there's no standby power and the remote cannot turn on the TV. Once the TV is turned on, the relay closes normally, so you could move the switch to the OFF position and nothing would happen. Power usage appears unchanged, about 3W in standby regardless of the position of the switch. The switch itself is sort of redundant in this configuration, but I thought it best to have a way to bypass the hack in case the unit is left unattended for a long period of time but not unplugged.

[R_J]

See if this is any help

[gintama]

Hah, yeah that would probably be quite helpful! I'll take a look, thanks.

[jeffinpeggs]

I would like to thank you all for your input, and especially gintama for the bypass instructions and photo. I had the same problem and after testing I found one bad cap. After replacing it I still had no power and stumbled upon this forum and post. Tv is now working after applying the bypass, Thank you very much.

[gintama]

Originally Posted by jeffinpeggs

Thank you very much.

I'm glad to hear it helped. Thank you for reporting back about it. I wonder how many more of these sets have failed this way...

[RyanM]

Which relay is that?

Originally Posted by gintama

Oh my. That was... embarrassingly simple. After ernest's post above, I took a closer look at the relay, to find that there's a clearly visible line where the housing goes on, and even large clips showing it's intended to be removed. I gently pressed on the side of the housing to see how loose it was - and it just popped off. I had no idea they weren't sealed units.

So I verified all the connections were in order, applied power, and manually closed the relay... After hitting the power button, the set lit up fine. Plugged in a old game system, audio and video seem normal.

Not sure what to do now. As I understand it, this narrows down the problem to the stand-by circuit. That relay connects the 120V lines, so as a last resort I could rewire the "Power Saving" switch on the TV to manually bridge that connection (instead of breaking the 120V circuit before the power supply like it does now). I'd prefer to fix it properly though...