Sanyo DP46849 46" LCD - Does not power up.

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

EN/UV to SOURCE is suspicious. EN/UV is supposed to either connector to DRAIN (for undervoltage lock out) or across an optocoupler... 330 ohms is very smaller.

[budm]

Re: Sanyo DP46849 46" LCD - Does not power up.

Hmm, what happen to my reply on the EN/UV pin, yes, it is way too low. Can you remove the IC and measure the resistance again without the IC in place?

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

EN/UV to SOURCE is suspicious. EN/UV is supposed to either connector to DRAIN (for undervoltage lock out) or across an optocoupler... 330 ohms is very smaller.

Hmm, what happen to my reply on the EN/UV pin, yes, it is way too low. Can you remove the IC and measure the resistance again without the IC in place?

Tomorrow I will remove IC and re-test EN/UV to 4 Source pins.

I also received a reply in e-mail from the forum that didn't show up in the post...

I ordered some 47 Ohm 1W resistors since I couldn't find any in my stash,

You can use a CR2032 3V battery or two AA batteries in series instead. Most PS_ON pins wii go high with 3V. The postive terminal of the battery goes to the PS_ON pin and negative goes to ground.

Should this be attempted before removing the IC or was it removed from the post purposely?

[retiredcaps]

Re: Sanyo DP46849 46" LCD - Does not power up.

You can use a CR2032 3V battery or two AA batteries in series instead. Most PS_ON pins wii go high with 3V. The postive terminal of the battery goes to the PS_ON pin and negative goes to ground.

Pay no attention to my post above. I had multiple windows open and cut & paste into the wrong window.

That is the problem with having 2 lcd screens and multiple windows open.

[retiredcaps]

Re: Sanyo DP46849 46" LCD - Does not power up.

Nothing looks obviously shorted with the IC.

And this why it helps to have multiple inputs on the problem. Obviously, my brain was somewhere else with my incorrect post (3V battery).

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

And this why it helps to have multiple inputs on the problem. Obviously, my brain was somewhere else with my incorrect post (3V battery).

Thanks for the info. I only mentioned it incase there was some forum glitch and it got lost unintentionally. I'll get that IC out today and retest. My 47 Ohm 1W resistors won't be here until Thur/Fri most likely.

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

EN/UV to SOURCE is suspicious. EN/UV is supposed to either connector to DRAIN (for undervoltage lock out) or across an optocoupler... 330 ohms is very smaller.

Hmm, what happen to my reply on the EN/UV pin, yes, it is way too low. Can you remove the IC and measure the resistance again without the IC in place?

Just got the IC off the board, despite my desoldering pump committing suicide midway through the procedure (The plunger flew out of the end and landed somewhere in the shop. I didn't even look for it, I ordered a new one.), and pin 1 EN/UV to any of the four S (Source) pins (5,6,7,8) still read ~330 Ohm. (329.95-300.01). I doubled checked to make sure I'm getting Pin 1 right, and confirmed it as it has the tell-tale dot on the IC itself, as well as the pin configuration (3 on one side, 4 on the other).

Does this lean toward a bad IC? I wouldn't be surprised if it's not the only bad part in this unit, but progress could be fun.

OK, check this diode..

I had the iron out so I lifted one leg and checked that diode from earlier. Here are the results:

Black on Anode, Red on Cathode = 0 VDC
Red on Anode, Black on Cathode = 0.2215 VDC

I also got the full part number, it's in 2 lines:

LT746
SB560

Still waiting on resistor for load to test voltages on the IC that I removed.

[budm]

Re: Sanyo DP46849 46" LCD - Does not power up.

So you you are still readin 300 Ohms on the IC pin?f that is the case, more likely that IC is bad. I would get another one.

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

0VDC, or "OL"?

The TNY IC is failed. Perhaps a power surge killed it. It is strange that power surges seem to happen a lot in US, but I've never seen a single device in the UK damaged by such!

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

So you you are still readin 300 Ohms on the IC pin?f that is the case, more likely that IC is bad. I would get another one.

Yes, still 300 Ohm between Pin 1 and any of the source pins (5, 6, 7, 8). I'll order another one for starters.

0VDC, or "OL"?

The TNY IC is failed. Perhaps a power surge killed it. It is strange that power surges seem to happen a lot in US, but I've never seen a single device in the UK damaged by such!

Definitely 0 VDC and not OL. With you being the 2nd recommendation of replacing that IC I'll try to locate and order one tomorrow. I'm guessing this was the result of a power surge. There are 3 TVs that I'm working on from the same location as a result of a surge. One was simply a blown fuse and is back in service, the second needed 2 capacitors replaced to bring it back to life but I've also discovered that all the HDMI ports have failed while other ports work (I'm thinking main board at this point), and the third is this TV you've all been helping me with that appears to have a sick power supply.

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

I have never seen a diode fail with a 0V and 0.22V measurement. You have discovered a new form of zero-drop semiconductor that engineers have been trying to make for years... shame it has only a 0.22V reverse rating . Please test it again for my personal sanity. Consider ordering a replacement for your personal assurance... and mine.

[budm]

Re: Sanyo DP46849 46" LCD - Does not power up.

If it is that shorted, you should be able to see O ohm on the Ohm meter.

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

I have never seen a diode fail with a 0V and 0.22V measurement. You have discovered a new form of zero-drop semiconductor that engineers have been trying to make for years... shame it has only a 0.22V reverse rating . Please test it again for my personal sanity. Consider ordering a replacement for your personal assurance... and mine.

If it is that shorted, you should be able to see O ohm on the Ohm meter.

Oh, wow, I didn't even catch that. My personal sanity is now in question and I can hear my high school electronics teacher scolding at me for not paying attention. I was rushing to get out of the office, at the time I was sure it didn't read OL, but now I'm questioning it. When in diode test on the Fluke 189 I know it'll show OL, but I tried it twice and it just read 0 VDC? (I think.) I'll check it again using diode check and resistance when I get to the office tomorrow. Would make sense to order another since it'll likely be inexpensive and I'm going to get taken to the cleaners on shipping anyway with only shipping one IC anyway.

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

If you do find this device has a zero-volt drop, send it to the semiconductor lab at my university as they'd probably be interested:

Institute of Microwaves and Photonics
Electronic and Electrical Engineering
University of Leeds
West Yorkshire
UK

But I'm betting it's OL and 0.22V

[budm]

Re: Sanyo DP46849 46" LCD - Does not power up.

I would like to send that to my friends at Fairchild semiconductor also (I worked there for 10 years).

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

Tell you what, we can split it in two and send it to both labs.

[retiredcaps]

Re: Sanyo DP46849 46" LCD - Does not power up.

I'll buy the defective Fluke 189. PM me.

[tom66]

Re: Sanyo DP46849 46" LCD - Does not power up.

I'll buy the defective Fluke 189. PM me.

Would you also like to buy 60 defective Agilent U1241B's?

My university lab is full of them and every... single... one has a defect where when left alone for several minutes, it will go crazy and start reading massively positive or negative voltages, 0V on diode test no matter what's connected and 100 or so ohms with the probes open.

Lab tech says they're due to be upgraded in a year or so, and if they end up throwing these out, I'm sure as hell grabbing some. Apparently, they just need a firmware update...!

[retiredcaps]

Re: Sanyo DP46849 46" LCD - Does not power up.

Lab tech says they're due to be upgraded in a year or so, and if they end up throwing these out, I'm sure as hell grabbing some. Apparently, they just need a firmware update...!

Some? Grab them ALL.

I'm very surprised at the lack of action with these malfunctioning multimeters.

People are supposed to trust the readings before taking potential action. For example, if the Agilent reads 0V across the legs of a large filter capacitor which in reality is charged to 400V, there could be serious problems if I start to desolder it.

As you are aware, Dave Jones, has found a lot of problems with the Agilent handhelds and if they were never firmware upgraded, it could be an easy fix (don't forget to send me one). A lot easier than picking up massively heavy monitors and repairing them.

PS. To show I'm not a Fluke fanboy, Fluke have their own problems as evidenced in this latest recall of products.

http://www.fluke.com/fluke/usen/support/safety/

http://www.fluke.com/fluke/usen/supp...37X-Recall.htm

January, 2013

Description of the problem

The printed circuit assembly may not be properly fastened to the test lead input jack. This may result in inaccurate voltage readings, including a low or no voltage reading on a circuit energized with a hazardous voltage, presenting a shock, electrocution or thermal burn hazard.

[Deebeaux]

Re: Sanyo DP46849 46" LCD - Does not power up.

If you do find this device has a zero-volt drop, send it to the semiconductor lab at my university as they'd probably be interested:

Institute of Microwaves and Photonics
Electronic and Electrical Engineering
University of Leeds
West Yorkshire
UK

But I'm betting it's OL and 0.22V

I would like to send that to my friends at Fairchild semiconductor also (I worked there for 10 years).

Tell you what, we can split it in two and send it to both labs.

Bad news guys, I haven't made any sort of revolutionary discovery. Definitely 0.22V and OL. I saw a O and the VDC in the corner lit, so I went with it. Was trying to get out of the office at the end of the day, seems to effect accuracy around here. I'll just change my nickname to "zero-volt drop" since I doubt I'll ever live that down.

Will order the IC today and replace and then go from there.

I'll buy the defective Fluke 189. PM me.

Sorry, Fluke 189 doesn't appear to be defective, the operator however...