Author Topic: It's been a tough day  (Read 875 times)

TC Chris

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Re: It's been a tough day
« Reply #15 on: June 14, 2017, 07:19:55 PM »
When I was a kid, you could fix a TV, but maybe not a cat.  Now we've got great veterinary medicine so we can fix cats surprisingly well, but TV sets are a mystery.  Actually, that's probably progress, because for most of us pets are really more valuable than TV sets.  I've still got my parents' first TV, a 1953 Zenith console, but I don't have the same kind of affection for it that I've had for various cats & dogs.

By the way, I've tried the soap, hair, and stink deer remedies.  Actually, the neighbors tried the stink remedy but the smell migrated.  The first two didn't deter hungry ungulates and the third option was a cure that was worse than the disease.  I'm waiting for a plague, or maybe an outbreak of poaching.  Anybody who wants venison, I'll send a map.

Chris Campbell

electra225

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Re: It's been a tough day
« Reply #16 on: June 14, 2017, 10:44:15 PM »
The golf cart project is stalled waiting for suspension bushings.  A little over two months waiting for backordered bushings.  Other than that, progress is being made.  I have to brush up on my engineering skills a bit to build the bumpers, but after a couple false starts, things started progressing more normally.  The painter is on the case, the tires are ordered and the widgets like the OOOGAH horn, mirrors and the driving lights have been sourced. 

We are watching our old 1992 RCA Home Theater, a 32" console that cost nearly $1400 new.  I just did not have the heart to toss it, so it sits in the living room collecting dust.  Then when the new flat panel takes a dump, guess what comes to the rescue.  It has a lot better audio than the flat panel, but a 32" CRT set, huge in its day, looks tiny compared to a 55" flat panel.  I understand that the unreliability of flat panel sets is almost that of the old tube chassis CRT sets from the 1950's.  Apparently, it is so bad that TV repair shops are coming back.  You could not break the solid state CRT sets from the middle 1970's to the end of the CRT days, so the TV repair shops all died off.  Two or three years ago, NOBODY worked on flat panels and parts were non-existant.  Now, at least a cottage industry supplying parts has sprung up.  Most of the books on flat panel repair that I have seen are out of China.  I have not checked to see if Howard Sams Publishing puts out a book on flat panel repair.  I read where guys on other forums claim that flat panel repair is like falling off a log.  They are either extremely lucky or not very honest.  Most claim capacitors in the power supply are all that ever goes wrong.  I beg to differ.
If it ain't broke, call me.  I can break it....

19and41

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Re: It's been a tough day
« Reply #17 on: June 15, 2017, 03:18:47 PM »
It's hard to say who would consistently make a bad set because so many come from the contractor de jour and they can be better or worse than the going appraisal.  I hope the repaif kit pans out.  Solid state can't be that alien a province.  I would like to get a monitor at a thrift store and try repairing it.  I'd just settle for the time to do it in.  ;D
"Any sufficiently advanced technology is indistinguishable from magic."
Arthur C. Clarke

electra225

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Re: It's been a tough day
« Reply #18 on: June 15, 2017, 05:17:25 PM »
There are seven different versions of the chassis in this model TV.  Seven.  I need number five.  Not in stock, back ordered.  They cannot tell me when the repair kit for my set will be available.  "Could be a week, could be a year.  Just depends on demand."  Great.  I understand that it is the "most popular" version for what that is worth.  I won't share the name of the outfit that told me this.  I guess I go to Plan B, whatever that may be.
If it ain't broke, call me.  I can break it....

electra225

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Re: It's been a tough day
« Reply #19 on: June 24, 2017, 12:00:41 AM »
Plan B has actually been fairly interesting.  My wife is not thrilled by my "tinkering" since she has no big TV anymore until I decide what I need to do.  Since I am still learning, here is what I know to this point.

First, this TV, like every product with "RCA" printed on it currently produced has ZERO, even less than zero, factory support.  The horrible ON Corporation has no dependable phone number and none they will answer.  I have not found a scratch of printed service literature on this set.  Sams does not bother to mess with RCA stuff anymore, apparently.  Working on this set is like working on a 1930's orphan set.  Guessing is the order of the day in many cases.

Depending strictly on my experience working with old tube equipment, I remembered two facts about the failure of this TV.  First, it failed suddenly, while we were watching it.  It still had sound, at least for a time after the screen went dark.  Second, if this was a tube TV, I would be taking a hard look at both the power supply and the horizontal output section of the chassis. 

My first guess, based on information I got off YouTube was that since I have the red "standby" light on when the TV is plugged in, I need to take a hard look at the main board, which basically is the tuner, IF strip, audio section, power switch and video amp section of a "normal" old TV.  The power supply board is always "hot" when the TV is plugged in.  This PS board sends a 5 volt reference signal to the main board.  When the "on" button is pushed, whether by remote control or on the side panel of the TV, the main board sends another 5 volt signal to the power board, telling it to power up high voltage, in this case to power the LED back light panel.  The PS board also sends a 12 volt signal to the main board to power up the audio amplifier and the tuner.  Another 12 volt signal powers up the LED driver board and the T-Con (timing connection) boards.  The LED driver board functions like the video output section of a typical TV.  The T-Con board functions like the horizontal section and flyback of a typical TV.  My TV has no back lights at this point.  I also have no voltage at the plug from the power supply to the LED back light panels.  The chances of both back light panels failing at the same moment, even on a set known for LED failure is rather remote.  My next step is to put the base back on the TV so I can stand it up in operating position and where I can see the screen.  I need to connect my VCR to the TV so I can have an audio source, since there is no "white noise" with a digital TV running with no signal.  I then need to shine a flashlight on the screen to see if I see an image.  If so, everything on the TV is basically working, the main board is eliminated as the problem, and I need to find out why the back lights failed suddenly.  There will really be only two possible causes for dead back lights.  First, and certainly fatal, would be LED panel failure, both of them failing at the same time in my case.  Or, the power supply has failed, and is not powering up the LED panel.  I need to see around 100 (this is a guesstimation based on a Samsung set, I have no official information for this set) volts to the LED panel out of the power supply.  I'm not totally sure where I measure for this voltage.  The plug for the backlights on the PS board has a L+, L-, NC, NC, L-, L+ marking.  I ASSUME I measure both sets of "L+, L-" wires for the required 100 volts DC.  The way I understand it, if I see 100 volts, the TV should be working.  If I see like 130 volts, the LED panel is presumed to be bad.  If I see zero or substantially less than 100 volts, it is presumed the power supply is bad.  I will perform both the flashlight test and the directed voltage tests and we'll go from there.

When we work with our tube equipment, we concern ourselves with each point in the wiring and the voltages thereon.  Working with this TV we are only concerned with certain reference voltages.  Voltages on individual components is both unknown and unimportant.  This set is serviced from the module stage, if it can be serviced at all.  I still have not found a dependable source for parts, even if I convince myself of the exact module that caused the failure.  There are places that have parts for this TV listed.  I have yet to find one that will actually deliver the goods.  So I paid good money for a TV that "might" be usable for a time, "might" be serviceable if it breaks and I search heaven and earth for information how to fix it, and "might" be able to be fixed IF I can find parts.  Parts that "might" actually exist.

The power supply board for this set and other LED TV's is rather interesting in itself.  There is actually a heavy black line, approximately down the middle of the board, that separates the high voltage "hot" side from the low voltage "cold" side of the power supply.  The back light power supply is on the right, lower corner of the PS board.  It requires a 3.5 volt signal (present) from the main board to activate the power to the LED panel.  The LED panel is actually two pieces, consisting of six LED panels, each with six individual LED's.  The LED power supply consists of a transformer, two MOSFET's that serve as rectifiers, two diodes, and three 22uf@250 volt electrolytic capacitors.  There is no voltage that I have found on anything concerning the LED power supply.  I have not measured voltage on the transformer as that requires removing the PS board, which I have not done. 
« Last Edit: June 24, 2017, 12:32:03 AM by electra225 »
If it ain't broke, call me.  I can break it....

electra225

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Re: It's been a tough day
« Reply #20 on: June 24, 2017, 10:02:36 AM »
Further "testing" (I'm fumbling and guessing here!) has found no power to the LED panels from the power supply.  Since there are no back lights, I can't really see anything in the way of using the remote to get the VCR to work!  So I looked for the square graphic that says "No Signal" that comes up when you first turn on the set.  I shined a flashlight on the screen and found this graphic.  So, tentatively, that tells me that the TV is somewhat working, we just have no back lights for whatever reason.  And I have no power to the plug that goes to the LED panels from the PS board, with the LED's plugged in and unplugged.  So the first part I reckon I'll throw at this thing is the PS board if I can actually get one. 

My theory at this point is that an IC of some sort or a MOSFET has died and has killed the power supply for the LED's.  There is a theory that if the system detects a shorted LED, it will "shut down" to protect the PS.  I tried the "top secret" reset, pushing the "Menu" and "Vol-" buttons at the same time while holding the power on button for 60 seconds.  Then I repowered the set.  This is allegedly the "hard reset" mode, which did nothing.  This procedure, providing I have a live power supply, is supposed to cause the set to restart at least for one time.  I'm not sure I buy the "this set eats LED's" theory since there is so little factual information available on this set.  Who made this determination and what is their qualifications?  Methinks sour grapes by a disgruntled RCA owner has more to do with this than anything.  Like the old "dual 6X5 rectifier" whine propagated by some who have worked with old Zenith radios.  One guy has a problem, and it becomes an epidemic after it gets told several times.  I may indeed have a dead LED panel in the final analysis, but I am hesitant to call that an "epidemic."

I hear that the LED's will "short out."  LED stands for light emitting diode.  Can a diode actually short?  I can see them opening.  The LED's are all in series like Christmas tree lights.  If one opens, all the diodes on one panel go out.  So for both LED panels to be dead, at least one LED on each panel would have had to go open simultaneously.  Even my luck is not THAT bad.  That is still a possibility at this point.
If it ain't broke, call me.  I can break it....

19and41

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Re: It's been a tough day
« Reply #21 on: June 24, 2017, 11:10:46 AM »
If it is of any value to you, of all the sets that have had problems where I work, there has not been one that had the led backlight fail.  The power supply to them, yes, but not the backlight.  It looks like you might have isolated the problem in that power supply.
"Any sufficiently advanced technology is indistinguishable from magic."
Arthur C. Clarke

electra225

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Re: It's been a tough day
« Reply #22 on: June 24, 2017, 04:28:57 PM »
Your comment is certainly welcome, Rex.  I know you have way more experience with "modern" electronics than I do.  I feel more confident about this now.  It is fairly common knowledge that power supply issues are the most common when dealing with broken flat screen TV's.  I'll see if I can get a power supply board in my hand and go from there.  Thanks, again!
If it ain't broke, call me.  I can break it....

TC Chris

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Re: It's been a tough day
« Reply #23 on: June 25, 2017, 11:46:05 PM »
This has been an interesting discussion, and one the reveals the difference between analyzing a problem and just throwing parts at it until it goes away. 

Chris Campbell

19and41

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Re: It's been a tough day
« Reply #24 on: June 26, 2017, 07:31:24 AM »
The bad thing with consumer electronics like these is that the components used on the boards are difficult to identify unless you have a layout diagram.  That tends to restrict one to board level replacement with the exception of filter caps.  If they are identified with house part numbers, their values are difficult to get.  Greg is a very good analyst and has done well in getting to a problem in the set.  It is mostly is just not being intimidated by a different way of TV construction. 
"Any sufficiently advanced technology is indistinguishable from magic."
Arthur C. Clarke

electra225

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Re: It's been a tough day
« Reply #25 on: June 26, 2017, 07:31:29 PM »
With no service literature available, no schematics, no factory support, and the only discussion available at any price is on You Tube, (not known for dependability) one is at a loss as to how to competently proceed.  "Throwing parts at it until it's fixed" is the way guys "in the know" work on these things.  I tried using the logic that serves us when we work on an old tube Magnavox stereo.  Electrical principles still apply.  You still gotta have juice to it before something will work.  I'm not very proud of my journey into flat panel TV's.  I feel like an idiot.  I fumble.  I grumble.  Yet in all this, I feel fairly confident of the diagnosis and conclusions I have come to.  Nobody else has come closer.  If this actually fixes the set, that will be one of "those moments" when something works after you go to all the time and trouble.

And, thank you, Rex for your kind words of encouragement.  I trust your wise counsel.

Edit......My parts manager (the wife) informs me that an outfit in California has a PS board for this TV that is "in the mail."  Let's keep our fingers crossed.  By the way, if you need parts for a '63 Buick, a Magnavox stereo, or a Club Car golf cart, my wife knows where they are.  She is touting herself as the RCA parts guru.  I'm not as convinced as she is....... ;) 
« Last Edit: June 26, 2017, 08:03:32 PM by electra225 »
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19and41

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Re: It's been a tough day
« Reply #26 on: June 26, 2017, 10:11:07 PM »
Sounds like you folks have it made.
"Any sufficiently advanced technology is indistinguishable from magic."
Arthur C. Clarke

electra225

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Re: It's been a tough day
« Reply #27 on: June 26, 2017, 10:23:12 PM »
Let's reserve the "have it made" comment until we see the TV working again.  I found out a long time ago that things "go better" when my wife has input.  She can drive me nuts at times, but she is tough as a mate for a fight.  Having her look for parts gets her off my back about not getting the TV fixed.  I refer to this technique as "Constructive Obstructionism."  She gets to be "in charge" and I am no longer the bad guy.  She falls for it every time...... ;)
If it ain't broke, call me.  I can break it....

electra225

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Re: It's been a tough day
« Reply #28 on: June 27, 2017, 09:39:57 AM »
We got an email stating "Thank you for choosing XXXXXX electronic salvage.  We strive to provide high quality reclaimed and used parts for your TV........"  'Scuse me?  Reclaimed and salvage?  I don't think so.  I have one of those.  So, I cancelled the order and am forging on to NEW parts.  Surely if there are NEW TV's there must be NEW parts.

www.shopjimmy.com allegedly has 107 new power supply boards of the part number I need for this TV.  That should be plenty.  $10.03 shipping for one little board.   I ordered one and it should be here Friday.  We are not out of the woods yet.......
If it ain't broke, call me.  I can break it....

19and41

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Re: It's been a tough day
« Reply #29 on: June 27, 2017, 06:44:24 PM »
Hope it does the trick.
"Any sufficiently advanced technology is indistinguishable from magic."
Arthur C. Clarke