Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

[sattech200]

Morning All!

Just picked up a 40” Proscan, Model: 40LD45Q
Plug unit in and the red standby light appears. Press the power button and it turns to solid blue. It will hold this state indefinitely until you press the power button again or remove power. I removed the cover and did a close visual inspection of all boards, front and back and found nothing abnormal looking. The backlights do not even attempt to turn on. I hear no relay clicks or any other sound when the power button is pushed.

I have searched Hi and Low for a service manual or schematic and have come up empty handed. My thoughts are that the Mainboard is sending the signal to the power supply board but something is failing on the power supply board.

I replaced the capacitors, near the area of CON2F as shown in the pictures. (Those were just new oddball ones I had laying around, all I could find). The original capacitors showed no visual sign's of failure. I went ahead and replaced what I had to rule that out. (Desperately needing to order a cap tester!) My intention is to order a full cap kit once I figure out where the problem is. If I’m understanding this correctly, a low signal on the FB pin of CN3 is normal, that if it was greater than 2volts then a fault from the inverter board would be present.

Where should I start troubleshooting next? I want to dig deep into this power supply and identify the cause of the problem instead of just ordering a new one. Thank you for any ideas and suggestions.

Measurements of:
CON2F
`````````STBY Power ON
+5VSB 5.26 5.33
+5V 0.02 5.33
+12 0.0 13.30
+12 NC NC
ADJ .02 3.49

PS/ON 0.10 4.92
+5V 0.02 5.33
+12V NC NC
On/Off 0.02 3.43

CN3
VOC 0.0 13.3
FB 0.0 0.0
LD 0.0 12.6
LD 0.0 12.6

CON3F
24V 1.67 26.0
24V 1.67 26.0

(Sorry for the formating, not sure of a better way to do this.)

[notallbad]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Have to agree, those readings look good. I would say PS b/d too!

Good photos of the solder side of the PS b/d??

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

I've spent a solid day looking for service manual/schematics for this set and finally found this. Talk about waving a carrot in front of the rabbit. ughhh. Seriously wish I could find the full manual.
http://dc359.4shared.com/doc/qwaBqW_4/preview.html

I've started troubleshooting power supply but would really like to know what IC U2 is. Half the numbers are scratched off. I've used a couple different magnifying glasses and can only make out.
E6E....
SE6...

I've checked voltages at U1 (Inverter IC, OB3316QP) and all look good from what I can tell (based on my limited knowledge and experience) according to the datasheet I found here EXCEPT for the VS, I'm not clear on what that should be from the datasheet.
U1 Inverter IC, OB3316QP
1-ENA…….……2.75v
3-CS…………….1.27v
5-STIME……....0v
6-VS…………....0v
7-VDDA…..……5.17v
8-GATE2……….2.05v
9-GATE1……....2.05v
11-RI….………...2.40v
14-BF/DMOD..2.07v
15-DIM…….…..3.45v
16-SVD…….…..5.19v

One thing that keeps sticking in my head is that I haven't been able to identify any fuses on any boards of this set outside of the glass one on the main input.

Attached Pics are the backside of the power supply board RE46AY2502, AYL400203. I can try to get clearer pics if that will help any.

Any and all thoughts, comments or suggestions are greatly appreciated.
Thank you.
Randy

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Do you notice if the backlights flash for seconds? So far the inverter/power supply board is getting all the right signals.
By the way, this power supply board does not use 24vdc for driving the Inverter trnasformers, it uses about 380~390VDC voltage fro driving the transformer. Do you get about 380~390VDC on that large 450VDC main filter? Measure it right at the two legs, be careful you are working on the hot side of the circuits.
The section you asked about the ICs are the Cold side of the circuit for low voltage section.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

No, no split second flash, no clicking relay, I don't hear even the slightest indication of anything trying to start. Only the Power light turns blue and will stay that way until I hit the power button again. Have done that about 20 times now just to see.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Dang!! Was sitting here studying the board and had the thought of a bad solder joint. I went and started reworking all the joints around the HV transformers. Put board back in, hit the power button, after about a second the HV connector on the power supply started arching real bad and burnt the connector!!! I thought, well crap, maybe I didn't have it plugged in all the way. Since the connector was now burnt and unusable I soldered the HV wires directly to power board and went for round two. Same darn thing happened burning one of the wires off the board.
Hmmm......
I have brain freeze and need to take a break!! Back at it tommorow.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Should also note, that when I was reworking the solder joints I went ahead and pulled the two HV transformers and did basic resistance checks. They both were similar in values although I couldn't find what the specs were on them.

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

That means the inverter is working and putting out high voltage, otherwise you will not see the high voltage arcing.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

For the life of me I cannot explain what happened last night. I resoldered the HV wires and put everything back together and I'm back to where I started....and that's a good thing!

I am measuring 416 Vdc across the two legs of the large filter capacitor.

I don't know if I missed this before or if it's a slight change, When I turn the set on and have complete silence I can very faintly hear what I think is an oscillating noise coming from the HV transformers. It goes away when I turn the power off and no other signs of life.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

I have been beating my head on this all day!!!


But I'm learning new things and that why I do this! The set was free for changing caps on another unit so If I end up with a good working 40" out of the deal with spending little $ to repair it'll be a great day! (Plus I get to enjoy a nice frosty one if I pull it off!

After going over a bunch of stuff on the power supply and giving thought to what happened last night I decided to move my attention to the inverter board.
(I know it's not technically an inverter but I can't remember what the correct name was so I'm just using that for now).

Some of the voltages just don't seem right on the inverter board(but I don't know what the right voltages should be?), especially after watching this utube video. I know the bored in the video isn't the same but it is similar. I have 0 volts coming out of all the transformers when powered on (Meter set to AC mV).
http://www.youtube.com/watch?v=oE6K4xBVweA

I pulled two of the transformers from the board just to check resistance in an attempt to gain more information. I pulled the top one out of the 20 that are in line and I pulled the offset one closer to the center. I have no idea what the spec should be but guessing the top one is probably good.
P=0.7 Ohms, S=228 Ohms.

However I did find the reading a little odd on the center one, but again I'm not sure what the correct value should be.
P=0.5 Ohms, S=1.6 Ohms.

After giving this a little thought I decided to put the board back in without the center transformer in place just to see what the results were. I found no change in the symptoms from the test. Any idea what the purpose of that one is? (The offset transformer).

After giving this more thought I decided to try something. Everything on the set is hooked up like it should be except for the HV line. Offset transformer has been reinstalled. I took a spare bulb from another set and connected it to the HV output of the power supply. Wouldn't ya know it?? The bulb fired up and stayed on!!

This raises even more questions now....like what's up with the protection circuit? but that's not my main worry at the moment, just excited to see some sign of life and progress finally being made. Gotta take a break and digest this a little.

Budm, I just wanted to say thank you very much for all that you have contributed so far. It's helped keep me on the right track and I really appreciate that. Any suggestions at this point are greatly appreciated.

Thank you
Randy

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

The reading of good transformers should be with 3% from each other.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

It's a different transformer, different part number

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

The 20 good ones = 6601D
The 1 offset one is = 6602A

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

OK, the offset one is the current sensing transformer, it is not the same as the rest.
I was surprised that you do not even see the backlights flash since you are are able to get high voltage arc at the connector when it was not seated.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

I was under the impression all of the transformers were current sensing for the protection circuit?? What other purpose do they serve? The HV Line comes in and goes directly to the bulb connector. You know, as I sit here typing it got me to thinking/investigating. I'm in a hurry so won't have much time till a little later but I need to find a basic schematic, block diagram, etc.... explaining theory of what this board does.... Light bulb just went off. I checked resistance between the two terminals on connector mounted to the inverter board that the HV plugs into and I measure 0.4ohms between the two terminals. Is this normal?

I've attached a crappy pic, let me know if you need a clearer one and I'll get out the good camera.

I've had this itch to post my first you tube video. Not the best of videos and my Adobe skills are VERY rusty but I'm in a hurry to get this posted.

Two videos, First one showing the set with a spare test bulb connected directly to power supply, working normally as it should.
http://www.youtube.com/watch?v=ZVoFN...ature=youtu.be

Second video showing the set being fired up in total darkness to show no screen flicker is found.
http://www.youtube.com/watch?v=ZVoFN...ature=youtu.be

I also hooked my test bulb to each of the ten individual outputs (while the original bulbs were connected to the inverter). No change in symptoms was found.

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

If you look at the inverter board, there is a smaller connector with 4 wires? attached, there are label next to it, what does it say on those pin? This balancer board will send out two signals: one signal is for lamp current sensing signal, if one or more lamp draw too much current, it will send error signal to shutdown the inverter. Another signal is for Lamp detection if the lamp connection is open (you will have high voltage arcing if the lamp is not connected), it will send the error signal to shutdown the inverter.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Balancer board! Been driving me nuts that I couldn't remember correct terminology.

That is the CN3 connector listed in first post.
........Stby.....Run
Vcc...0v.....13.3V
FB.....0v.....0v
FB.....NC.....NC
GND... .....
GND...NC....NC
LD.....0v......12.6v
LD.....0v.....12.6v

(NC = No Physically connected wire)

From the documentation I found originally...and If I understood it correctly, the shutdown condition from the balancer board is < 2.0V on the FB Pin.

Another clue to the mystery. When I have the test bulb connected to the power supply, with the 4pin control wire connected to balancer board, it actually shutdown the test bulb 2 out of about 10 times that I powered it up that way. In most of the testing the test bulb was staying illuminated for the minute or two I performed the test. I would have thought it should have done the 2 second shutdown every time since no current is being drawn out of the balancer board.

[budm]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

All those voltages are correct for normal operation.
FB per SONY should be around 2V. So there is problem in the FB circuit.
LD normal = 11~12v, bad will be LO (<1V)

Sony uses basically the same setup as yours, so you may want to read this training manual on post 35.
https://www.badcaps.net/forum/showth...499#post368499

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Well, I have spent a Lot of time trying to identify the failed component but haven't been able to due to lack of service and information and experience. The resistance readings seem really odd on that oddball transformer and suspect it might be that. I even pulled ALL transformers from the bored and did resistance testing on each one.

At this point I guess I will order a balancer board as soon as the budget allows (wich might be a while) unless someone might be able to provide additional information on this problem...specifically tech info on the balancer board.

Thank you for any and all advice. I will update this post when progress is made.

[sattech200]

Re: Proscan 40LD45Q Power Supply not turning back lights on, no HV fault present.

Bummer! Finally managed to swing a replacement balancer board and still have the exact same symptoms....

Sure do wish I could find some service information on this set.... I hate having to swap test parts.