I have a friend with a malfunctioning TV and no job, so paying for repair is not likely, but is an electronics engineer, albeit silicon design and not circuitry.

Does anyone have any pointers on TV repair? The TV is a Sony CRT HDTV. I don't have the model number at hand, but the KD-36XS955 looks close.

The symptom is that the TV will sometimes simply not show video at all, sometimes failing to come on after being shut off, sometimes cutting out while it's on. It will also sometimes seemingly partially lose deflection, so that the picture becomes smaller for an instant. He has a trouble code that the TV is communicating via the power LED with a blink code. I don't have that at hand, either.

Between us, we can probably figure out how to break it more. Anyone want to help us actually make it better?

Tried looking for a service manual? Generally thre are a number of sites that offer PDFs for "sale" for $10-20. I highly doubt they are authorised to sell them so but I've bought a couple with no issue so far.

That LED blink code is definitely worth deciphering.

My XBR40800 did about the same thing. I ended up finding on the internet that it was a common problem and one IC needed to be replaced. I had a local repair come do it and he noted he had to do that same repair many times. The labor was 100.00 and I got the part online cheap.

Probably not the same thing since it's a different model but if you can't find it on the internet maybe calling a repair guy and asking might help.

Sets of a certain model will all have the same problem with the same thing. Just search usenet and see if there are any other postings for the same model.

I did a couple year stint doing tv repair and most of the time I didn't even have to plug it in to know what's wrong.

Sonys have an overvoltage detector for the crt high volts. This is just a wire that wraps around the back side of the crt and plugs into the pcb. I've fixed it before just by unplugging that wire.

My experience (chronicled here) was that the Internets were fantastic at diagnosing my problem. I ordered the replacement IC amps online, then when I extracted the board, it was clear that several resistors were fried. I found the service manual (free, on RapidShare or equivalent) to get the resistor values. All in all, not a bad experience, but I never would have gotten that far without the Internet to document how other people solved the very same problem.

What the others said. You need to acquire the service manual and do some digging on the internet to see if this is a common problem. Does the temperature of the TV affect it in any way?

If he is a polygon pusher then make sure he doesn't fry himself when poking around in there. 12V would be counted as "high voltage" for most of them :P

Just drain the caps with a screwdriver or other all-metal implement.

I recently wanted a new TV so looked at "faulty" ones on ebay. In a week or two I had:

- A 42" plasma (£70) with blown video inputs but VGA works fine, so I use that with a TV > VGA adapter I bought in HK and had laying around.

- A 32" HD LCD (£50) - described as "flashing red, green and blue" with no remote. I bought a replacement remote and pressed "menu" to get it out of burn-in mode.

- A 32" HD LCD (£40) - described as "green in the dark sections". Fixed by cleaning the LVDS connector.

I also have a 46" Bravia (KDL-46X3500) that has been dropped on one corner (damaging the bezel). The screen looks good but it's missing the UB1 board, I'm not sure if it's worth buying one because the screen might have been fatally damaged too.

Anyway Googling gets you a lot of info on TV faults, these sites are good:

http://www.tv.quuq.org/
http://www.eserviceinfo.com/
http://www.agoraquest.com/ - has lots of Sony stuff but the search function is crippled without a subs ($12).

fixya.com is appalling.

Service manual for that set is:

http://www.eserviceinfo.com/downloadsm/31560/Sony_KD-30XS955.html

Hi,

Long Email Alert - hit the delete button if you want to now.

Another thing to look at are capacitors. Electrolytic Capacitors are notorious for drying up in ALL Electronics. One of the first things to look for are capacitors near heat generating components (examples are...

1) Any Capacitor near a heat-sinked device
2) Horizontal Output
3) Flyback Transformer
4) Vertical Output
5) Pincussion Driver & Transformer
6) Audio Output IC
7) Power Supply components
8) Large heat-dissipating resistors
9) CRT Cathode/Grid drivers & resistors on the CRT socket card

Aluminum Electrolytic Capacitor have an Electrolytic paste inside and the high temperatures surrounding them plus no decent way to remove the heat causes the Electrolytic to either dry out and the capacitor loses its capability to store energy or the losses due to high Equivalent Series Resistance make it ineffective. To save cost, manufacturers usually install 85 Deg. C temperature rated capacitors. They should use 105 Deg. C rated capacitors in most locations.

The electrolytic also drys up because of high ripple currents in the capacitor (under-rated for the application to 2 cents - they expect them to fail after 4 years - sort-of encourages us to upgrade to new "technology"). In this case, the heat generated actually boils the electrolyte and the safety vent in the construction of the capacitor opens to expell the gas and the electrolyte exits through the vent. This can be seen as residue on the circuit board (often conductive - causing problems with other circuitry), that the small Panasonic SMT can
Capacitors are know for - they are called "fish Caps" becuase when someone opens up a product that has some of them that are bad - it often smells like "fish".

A quick identifier for these is that the top will be bulged or the outside wrapper will be "shrunk" around the top of the capacitor (others will have more of the plastic on top). The ones most prone to failure are the capacitors that are over 50V (the higher the voltage, the higher the liklihood of it being bad), because they are used for filter capacitors and usually have high frequency ripple currents that stress the electrolyte paste dielectric and then are further compromised by locallized heat sources.

If he wants to keep the TV, and you want to help him, you need to replace some of the capacitors. You will need to aware of some safety information FIRST, so read all of what is below, BEFORE YOU START.

*** Caution and Disclaimer *** If you have not been inside a TV or exposed to high voltages, I advise you to have it serviced by a qualified Service Technician. The information here is my own oppinion only for "entertainment purposes" and I accept no liability for injury caused by following any of this information.

Always work with one hand in your pocket (use only one hand while working near high voltage to prevent the current going through your body from one hand to the other) on an insluated (ungrounded), surface. Many people have been injured or killed by being careless around high voltage. Not always by the electrical shock, but, by being thrown into something by the convulsing of the body muscles when excited by the shock.

Do not strike or scratch the Cathode Ray Tube (CRT or picture tube). It is constructed with a vacuum inside and being a large device, if the vacuum is compromised, the CRT actually implodes sucking all of the glass inward and then expellinging it EVERYWHERE as glass shrapnel causing great injury. ALWAYS have safety glasses on when working near CRTs and exercise extreme caution. Limit the number of by-standers, they could be injured too.

The CRT is actually a large surface Glass Dielectric Capacitor. There is an inside coating of auqadag (a sprayed metal coating) that attaches to a metallic button on the bell shape of the CRT. This inside coating is called the High Voltage Anode connection and is also the positive plate of the capacitor. There is the physical Glass material construction of the CRT bell, which is the dielectric of the capacitor. There is also a metallic spray coating black soot looking coating on the outside of the CRT. The outside coating is the negative plate of the capacitor. The negative outside coating is usually connected to High Voltage Ground by a spring wire that goes around the CRT bell or the CRT frame. The CRT High Voltage is used as a post accellerating potential to pull electrons from the CRT gun to the faceplate phosphors (what we watch). The CRT being a capacitor is also used to filter the high voltage.



Before you do anything inside the TV, un-plug it and leave it off for a day.

Remove the back cover, connect a long known-good clip-lead (check it with an Ohmeter before you use it) ** One hand in your pocket **, to the metal band spring wire that surrounds the back of the CRT or attach it to the metal CRT attachment frame. Attach the other end to an insulated-handled long screwdriver.

** One hand in your pocket **, - visually - locate the High Voltage lead wire going to the CRT. This will attach to the CRT with a rubber button cover. Using the screwdriver with the wire attached and already connected to the CRT ground wire or CRT mounting frame above, slide it under the cap (being careful not to scratch the CRT). Prepare yourself for a small audible "snap" from the high voltage arc discharge - so that you are not startled and injure yourself. Leave it shorting for 30 seconds.

** One hand in your pocket **, use the screwdriver blade to lift the cap some and use a flashlight (use the other hand too) to locate a mechanical clip or double spring wire clip to the CRT Anode attachment. Use the screwdriver to lightly push on the attachment to remove it from the lip of the CRT Anode attachment. Use the screwdriver blade to do the same with the other spring wire clip to remove the cap. Remove the screwdriver from the clip-lead and attach the clip lead to the CRT Anode connection to continue the discharge (they can self re-charge to a lower voltage). Leave the clip lead there until reassembly - but, remember to remove it when you reassemble the TV.


If he wants to keep the TV, it's a good idea if you open it up for anything else, take detailed pictures with a digital camera of the above areas, find the capacitors in those areas that are suspect (by the way that doesn't mean ALL capacitors in the TV will be bad, just those suspect near the heat generating devices), note the value and polarity of each component (the stripe down the side is negative - by-the-way - I have seen NEW capacitors that actually have the strip being (+)), and unsolder them. Take them to a GOOD (not Radio Shack, they won't have them), Electronics supply house (Capacitors are usually cost less than $2.00 each - you may replace around 15 in a typical TV), and purchase 105 Deg C capacitors to replace them. Be sure to notice that the Vertical Output coupling capacitor may be a Non-Polar capacitor, be sure to get one that is non-polar if it is.

While you are there, check all high temperature connections for cracked solder or heat stressed fractures and connections. Re-solder those with 60/40 rosin-core solder (never acid core for electronics work). Many resistors, transistors, MOSFETs, Diodes, transformers, capacitors, inductors, etc. generate lots of heat and compromise their solder joints over time. Check grounds solder connections too.

Also check the small value resistors coming from the Flyback or Power Supply areas. Thse will be usually less than 10 Ohms and they are used as current limiters and fuses when the capacitors dry-up as the ripple currents are high (by not being filtered as well), voltage goes down - still need the same power - so, current goes up, stresses or blows the resistors).

It might also be a cracked PC-Trace too (even on the push-button switch panel), look for that as well especially if the TV has had rough mechanical treatment.


Re-assemble after you have done the above things, be sure to remove the CRT shorting clip-lead. Re-check everything before the cover goes on. Power it on and see if that fixes it.


Good luck, hope you can find the problem and wait for the next thing to break.

Ross

+2 for capacitor check. Nearly everything that breaks around here, except for the empegs, is due to bad/expired caps.

As for TVs.. our Viewsonic 37" LCD has one (of 12) backlights not lit. I disassembled as much of the set as I could to try and access it, but hit the point of too many pieces and gave up -- reassembling it while it was still possible.

None of my voltmeters go high enough to verify the 1300V supply lines to the tubes, though all of them appeared to have more than 700V live.

Cheers

Sounds like it's time for a new toy!

Hi,

You could make yourself a HV Divider with the 10 MegOhm (or whatever Volt-Ohms input impedance of your DMM and few 10 MegOhm series resistors. Be sure you ues wire that will support the withstanding voltage. Just scale the output per the voltage divider value.

Ross

I did find this wonderful CRT repair video guide which may come in handy.

I read that as "CRT repair video game". That would have been interesting.

This is very interesting. And, it brings to my mind a question on what MB would you guys buy today, if I wanted something good and long-lasting, for my personal PC? Any Brand/Model that you would recommend for its quality components on board?

The only motherboard I have ever had die here, for any reason, was the VIA Mini-ITX board in our server. Sure enough, the capacitors burst. I replaced all of those (last year), and now it is fine again.

No other motherboards here have required service over the past 20 years. Most of them here are by ASUS and Tyan. Duke, our PVR, has a FoxConn motherboard.

EDIT: actually, one ASUS board I purchased second-hand had to be sent in for warranty service, as the SDRAM sockets were not all functional.

I have replaced the odd lithium-based battery on some motherboards -- those are normally good for up to 10 years or so.

Cheers

Hi,

I second Mark on the FoxConn motherboard. I have a BloodRage in my i7 simulation system. It has what they and others term as "Solid Capacitors". These are contructed from an Organic Conductive Polymer material instead of the Electrolytic Paste or fluid.

They are said to last 20+ years instead of the 4 years I mentioned earlier. I think they are right.

The one thing to remember with ALL electronics (not so much with vacuum tube based equipment - except - you guessed it Electrolytic CAPACITORS) is that heat kills. Often, running a system 10 Degrees C cooler doubles its lifespan. If you want reliability and long life, keep it cool!

With many tube based Electrolytic Capacitors that failed, they were multiple sections in a common metal can mounted upright to the chassis. When they fail they are either not available or extremely expensive. What many do, is remove the bottom cover of the can, remove the dried-up capacitors, replace them - stack them inside the original can - with 105 Deg C. Electrolytic Capacitors (much smaller these days than what was in there originally), put a similar cover back on the bottom, and reinstall them into the equipment.

Ross