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Chat / Re: It's been a tough day
« Last post by electra225 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!
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Motorola / Motorola SK16W
« Last post by heats00 on June 24, 2017, 04:07:40 PM »
Found this for $40.  The cabinet is in pretty good shape and should clean up very well.  One small tear in the grill cloth.  It works as found, but the turntable will need to be cleaned and re-lubed, and the dial string will have to be restrung.  I would love to find the matching speaker to this!

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Chat / Re: It's been a tough day
« Last post by 19and41 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.
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Chat / Re: It's been a tough day
« Last post by electra225 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.
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Sale or Trade / Modern Walnut RCA SHF-2 For Sale Toledo Ohio
« Last post by bastardbus on June 24, 2017, 12:17:02 AM »
Recently found a Modern RCA SHF-1 and going to be letting go of my Modern SHF-2.  Located near Toledo Ohio.  Lots of pics and details.  Shoot me a PM if interested in discussing details, would prefer to chat on the phone. 

No tire kickers or dreamers please, serious inquires only.

email is oldvw@yahoo.com

Thanks
Todd
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Chat / Re: It's been a tough day
« Last post by electra225 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. 
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Motorola / Re: Motorola Stereophonic restoration at last
« Last post by Motorola Minion on June 23, 2017, 04:52:09 PM »
First, I measured the resistors and found all to be within spec. I also checked the primary resistance on all three output transformers, hoping for the best and all were close to resistances on the schematic.  ;D

Most Motorola products work as found due in no small part to the extensive use of ceramic disc caps in place of wax-paper caps for values .001 through .05 in. But due to effects of temperature and vibration on capacitance, ceramics have limitations in coupling and emphasis'/de-emp networks. Mylar film caps will replace them as I have done with two of my Magnavox amps.

The amp chassis is pretty shallow, so installing electrolytics under it requires some careful placement and the use of a 5-lug strip. this should be pretty clean when its done and I will label the caps with half-circle, square, triangle and dash to match the 4-section can designations, also shown on the Sams schematic.

Typically, I solder all the film caps across the ceramics, then cut them out when trimming all the leads. It ensures I double check old and new values before removal.

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Sightings / Re: Magnavox American Modern Lawrenceville, GA
« Last post by TC Chris on June 22, 2017, 11:55:35 PM »
It's a handsome thing. 

Chris Campbell
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Sightings / Re: CL: 1958 Fisher C-800 $350 -- San Diego, CA
« Last post by Harbourmaster on June 22, 2017, 09:08:28 PM »
Good idea except for the fact that right now the back of MY vehicle is full of a nice white iron trundle bed that I picked up off of the curb 3 weeks ago and it's still rattling around in there waiting for me to find a couple of hours to shuffle more stuff in the garage in order to make space for it until the girls are both big enough to actually use it.


AND


I'm going to the wedding with the wife and youngin's, and I think she might notice if I stopped off to load a console in the back of her mini van.


AND


I'm still trying to figure out what to do with the 2 other consoles I have stashed at work before the new manager shows up and asks "what the hell are these doing here?"



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