Circuit Board Electricians

[Jeff Matthews]

Anyone here work with electronics enough to "expertly" give advice on diagnosing why my 50" Sanyon plasma turns itself off and back on? Sometimes, it screeches with a loud alarm as it turns off. Sometimes, it does not. There is no issue with the picture or sound.

[JJkizak]

Well let's see. you will need a complete book of schematic diagrams ( usually about $140.00) for your model with test procedures, and about $5000.00 worth of decent test equipment and test leads before you begin touching any of the guts inside. If it has internal calibration then you will need the break-in code to set everything which you get from the manual after you fix the thing---if you can get the new part (maybe impossible or the new board (probably $250.00 minimum) maybe six months after you order it. Why screw aroiund with it---just set it on the curb and buy a new one.

JJK

[Jay481985]

Jeff it sounds like a bad capacitor. I suggest googling you tv with "sanyon X problem" and see if its a known issue. Samsung had a model with cheap and bad capacitors that blow in a year or two and most people junked them. Some would google it and replace the board or if you're good with soldiering change the capacitor itself.

[JL Sargent]

I had a TV that was turning itself off like that. I carefully poked around the wire connectors with a plastic screwdriver and found a cold solder joint on a wire end. I soldered it up and all has been good since. So I guess it cost a whole nickles worth of solder.[]

[Marvel]

I would, without having the tools for diagnostics, say it might be a cracked trace or bad solder joint. A cracked trace/board, will flex as it heats and cools, creating all sorts of havoc. Good luck!

Buce

[gagelle]

This guy on Ebay was selling vintage equipment at inflated prices claiming to have restored them himself. I was a bit suspicious because he never was specific about what he did. So I sent him one question: Do you have an Oscilloscope? His answer was, "no, I do it by feel."

[pite]

The guy on Ebay must be fortunate enough that he didn't happened to meet PWK!

fix the electronics by feel = [bs]

[pite]

When you say 'screeches with a loud alarm' you mean 'loud screeching sound'? Seems SMPS (Power Board) that powers the various circuit boards, panel, etc. might have an issue or a defective power semiconductor component. Some times you might be a lucky one, having a 'Cold Solder Joint' that you can find and resolder/fix.

It's hard to tell you which component on the board is causing it, without looking at the schematics. One thing to make sure, that please don't touch or solder when the TV is on or pluged in (possibly in stand-by mode). Turn OFF the TV, wait for good 3-5 minutes to discharge stored energy from the capacitors and then disconnect from the wall outlet before opening it and touching anything inside. The power board might be generating enough power to cause you harm (upconverting to very high voltages from 110VAC) for your plasma screen.

[JL Sargent]

This guy on Ebay was selling vintage equipment at inflated prices claiming to have restored them himself. I was a bit suspicious because he never was specific about what he did. So I sent him one question: Do you have an Oscilloscope? His answer was, "no, I do it by feel."

Not so fast. A tech could replace every capacitor, resistor, OPTs, and tubes in an amp without a scope of any kind. What he should have said was that his (brain/ear) was better than any scope. To that answer I would be more inclined to agree.

[pite]

If Restoring = Change everything on the board without diagnosing/checking, yes one can do it that way. A time consuming, very expensive affair, performance altering and might introduce a issue as it's done without understanding to begin with. And, regarding the audio at that point it becomes a individual preference.

Imagine, how expensive it will be if technician starts replacing all components on the board without measuring and analyzing the signals. Even the very simple to work with cross over consisting capacitor, inductor, resistors could become a costly affair.

May be right there, that's your answer, why he had 'inflated prices'...

[JJkizak]

And if there are custom unidentified control chips how do you substitute those without harming perfomance?

JJK

[pite]

And if there are custom unidentified control chips how do you substitute those without harming perfomance?

JJK

On that subject, there is no way one can work - good chances of destroying it...Imagine working with 60nm/45nm/30nm Audio-Video processors, ASICs, DAC, etc.. Even the amplifier chips are quite small being SMDs. If they are BGA part, forget it...Without hi-end equipments to desolder and solder there is no way one can work with typical 'Soldering Iron Station' that we use otherwise for cross overs or making cables etc (coarse work!)... Not to mention, wave soldering is used when they are populated on 8 to 10 layer PCB (Printed Circuit Board).

All in all, we stay away from desoldering and soldering by hand. Once the defective componenet is identified on the PCB, a highly skilled technician is deployed to work under a microscope to connect those fragile/thin legs of ICs to the pads on the PCB while mainitaining the time and temperature for a given solder joint. Too much temperature or too long at the given soldering joint and the pad comes off the PCB or the IC is destroyed...

And if you touch it without proper grounding equipment, the static charge/power may damage the IC, amplifier, or a transistor...Too much price for a curiosity!

[Marvel]

pfffft...

I worked on surface mount chips with all the wrong equipment while working for a gov. contractor.... you just have to be careful. A good magnifier while soldering and a reasonable soldering station means it is possible.Small pitch surfacemount chips canbe replaced with no problem.

Bruce

[pite]

pfffft...

I worked on surface mount chips with all the wrong equipment while working for a gov. contractor.... you just have to be careful. A good magnifier while soldering and a reasonable soldering station means it is possible.Small pitch surfacemount chips canbe replaced with no problem.

Bruce

Works for you! Unfortunately, not for us with today's 30nm/45nm SMDs and BGA parts... Not to mention that we can't pass the audit!

[Marvel]

Not to mention that we can't pass the audit!

There is that ... []

I didn't have to do it very often. We had some prototype neural network boards with some custom chips on them. The company in Huntsville did the assembly, and they weren't always the neatest.

[gagelle]

I'm an amateur in these matters but I've read that a scope will reveal distortion or clipping that is not detectible by the human ear.

[pite]

very true...often one won't here the content. That's the one reason that tube/valve amplifier sounds smoother and revealing. The part of the frequency peak (amplitude) which is clipped otherwise in solid state is available through tube/valve amplifier as it doesn't go in to clipping mode, thus allowing speaker to reproduce it.

[deafbykhorns]

Plasmas have a circuit that sense overheating

Its in the power supply which are about $300

[USNRET]

I have a Vizio Plasma that would do that. A few minutes on the web gave me the info and $11.34 worth of caps (shipping included) fixed it right up!

[JL Sargent]

I had a VIzio LCD that would turn itself off on the video while the audio continued on. I figured it was the power board with a problem. It was under warranty, they sent a guy out that couldn't fix it. I boxed it up and took it back to the store for a swap with a different brand unit. All good with that one, Philips.