How convergence circuits work

Convergence circuits correct the size, shape, and position of the scanned image (raster) by applying voltages and waveforms to the secondary (sub) deflection yokes on the neck of each CRT. These are windings in which a change in current results in a magnetic field that affects the behavior of the electron beam that scans the image on the phosphor. These yokes have horizontal and vertical windings similar to deflection yokes, but carry much less current and much lower voltages. Still, controlling the beam with the precision needed to match the images in all three tubes requires a reasonable amount of power. The amplifiers that drive these yokes are similar to those used in less expensive audio applications such as lower end receivers and portable (boom box) devices.

There are six channels that need to be amplified, horizontal and vertical for red, green, and blue. Most systems use integrated circuit designs with 2, 3, or 6 channels per chip. They are almost always STK series chips made by Sanyo. Some sets have used discrete transistors for these amps, but they are relatively rare. Most of the chips range in power rating from 20 watts to 70 watts. The run constantly when the set is on so they do tend to get hot. Temperatures in the range of 130 to 160 degrees F are not uncommon. Imagine an audio receiver running with the volume at a fairly loud level constantly. This is what these units do. Consequently, there are failures.

The correction starts with a series of waveforms applied to the amplifiers, along with a small dc offset. The waveforms are typically combinations of parabolas (for correction such as pincushion), sawtooths or ramp functions (for keystone and skew), and more complex patterns for point convergence. Vertical correction is applied at horizontal scan rates or factors and multiples of it, and horizontal correction is applied at vertical rates or factors and multiples of it. The chips must, therefore operate over frequencies that are typical of audio amps for conventional NTSC systems, and much higher rates for HD systems. The bandwidth of the ICs ranges from just adequate for NTSC as roughly 15kHz to over 100kHz, far beyond what is needed for HD applications. Most of the current chips have adequate bandwidth, some from a few years ago are marginal and should be upgraded to later versions. I will cover that in another post.

The dc offset is typically no more than a few hundred millivolts. Too much dc, or too much correction at the limits of the capability of the chips can cause them to run very hot. Heat is not a good thing for most semiconductors, so proper set-up is important. The dc offset is typically going to effect position changes (called static convergence) with little or no effect on the size and shape of the picture (called dynamic convergence).

The waveforms are generally generated in a circuit area called the convergence generator, which may be a separate module or combined with another set of circuits on a larger board. The correction signals are then applied to the input to the output ICs as a combination of the waveforms needed to correct the image. At that point the signals are in the hundreds of millivolts to perhaps a couple of volts. The output ICs amplify them and provide the power to drive the convergence yokes. They are usually powered by + and - supplies ranging from about 16 volts to 40 volts, depending on the design of the set and the chips chosen for that application.

 

The chips

This is a list of most of the commonly used STK devices and some that Sanyo made that are rarely, if ever, used. I will add links to the data sheets that I have, but some of them are not available. Some of the chips are versions made for a particular TV manufacturer, and Sanyo does not provide data on those, typically. It is generally best to use the same chip that is found in the set. However, there have been newer versions of some of these produced that are identical in performance and superior in certain applications. I will note my recommendations and the logic behind them, but I in no way, nor does HTS, take any responsibility for the accuracy of the information with regard to substitution of parts. Any substitution is your responsibility. I can only relate what I have found to work with parts that I know to be original Sanyo parts.


STK4273 replace with STK4274 if heat sink allows
STK4274
STK4275
STK4278

STK391-110
STK391-120
STK391-220

STK392-010 replace with STK392-040
STK392-020 replace with STK392-040
***The -040 has wider bandwidth and has higher current rating than the -010 and -020. I use in ALL cases to replace the older versions.

STK392-040
STK392-560
STK392-570

STK392-110 Hitachi replaces these with STK394-160, for other sets it may not be a good sub. The STK392-150 is a good sub in any set, IME.
STK392-120 Hitachi replaces these with STK394-160, for other sets it may not be a good sub.
STK392-150 Hitachi replaces these with STK394-160, for other sets it may not be a good sub.
STK392-180
STK392-210
STK392-220

STK393-110

STK394-160 (This is my choice to replace the STK392-110, -120, & -150 in most Hitachi sets and are available in the kits in the next post)
STK394-210
STK394-250
STK392-260
STK394-510

Suffixes
-L means bent pins for horizontal mounting
-E means lead free
-HIC in Mitsubishi parts simply means that it is an IC on a heat sink and is irrelevant to buying parts.

 

Buying the parts

Added note:

I keep getting lots of the same questions, so let me clarify a few points. First, if you do not buy the parts from one of the known reliable distributors, you may be getting counterfeits or seconds. Just because someone claims to be selling original Sanyo parts does not mean that they are good quality OEM parts. MANY techs and consumers have been burned. If you are DIYing, you are already saving lots of money. DO NOT take chances with cheap suppliers. You may get lucky and you may not. The problem is that you will not be sure and without the skills of an experienced tech (and even with them) you may not be able to figure out whether you have a problem with parts or botched the repair.

The STK394-160 has become a good replacement for the parts as listed in the post above. It was originally only available in the Hitachi kits. I still only buy them that way because I know that the parts I get through Hitachi have been reliable. Who knows whether the ones available through other channels are first quality parts, counterfeits, or seconds. I won't take the chance. The question of whether the Hitachi kits have the STK392-150 or the STK394-160 keeps coming up. They originally supplied the -150 in the kits. Some of the distributors keep telling people the kits have them because they may still have old stock with those parts. I have not seen a Hitachi kit with the -150 in many months. If you get them, they are still a far superior part to the original STK392-110, so don't sweat it.

There are many distributors that sell replacement parts for these repairs. Unfortunately, as many techs and shops have learned the hard way, not all of them are selling premium quality parts. There appear to be some cheap copies that have given results that range from OK to virtually 100% failure. It is highly recommended to buy parts that are known to be original Sanyo chips. The vendors that I have listed below have been found to be very careful sell only original Sanyo chips.

Most of these can be found in the Parts Distributors thread at

http://www.hometheatershack.com/for...m/forums/manufacturer-vendor-reference-information/4396-parts-distributors.html

I personally ONLY use these vendors for STK ICs. There may be others with good parts but don't ask me about them. These are the only ones that I trust enough to recommend without qualification. If you use parts from other vendors and you have a problem you are only adding variables to a process that already has many pitfalls. You can read through the various repair threads and see dozens of people who have had problems completing these kinds of repairs. Many are due to using cheap parts, many are due to service mistakes or not being thorough. In my experience it is not worth the risk to add variables to a repair, even with my experience. For a novice to do so is simply asking for complications.

ACME
B&D
Electronica (in Denver, NOT Electronix, DO NOT BUY convergence ICs from Electronix)
or authorized distributors selling the parts as supplied from the TV manufacturer.


Hitachi has put together kits for some of their models which contain two chips (usually an upgrade of the originals) and more resistors than most repairs require. It is often cheaper to buy the parts this way. The chassis number is on the label with the model number and/or on a sticker inside the set. However, these kits have become very hard to find recently.

These are the part numbers that I know of for the Hitachi kits:

Kit Part Number
Chassis
Models

X480293
DP14G
43UWX10B
53UWX10B
53UWX10B
61UWX10B
61UWX10BA
61UWX10BB

X480295
DP15
53UDX10B
53UDX10BA
61UDX10B

X480296
DP15E
43FDX10B
43FDX11B

X480297
DP15H
53FDX20B

X480300
DP07
53SWX01W
61SWX01W

X480301
DP05
53FDX01B
53FDX01BA
DP05F
43FDX01
DP06
53SDX01B
61SDX01B

X480302
DP17
53SWX10B
53SWX12B
61SWX10B
61SWX12B

X480306
DP25H
53F300
DP25K
43F300
DP26
57XWX20B
65XWX20B


You have to get these from a Hitachi authorized distributor. I buy a lot of parts for other brands in these kits because they come with either the STK392-150 or the STK394-160E. I use the latter to replace other versions as noted in this thread. It is cheaper than buying the chips individually and I get the resistors. Also, you can be pretty sure that Hitachi is getting Sanyo original ICs for their parts and not some cheap copies from another manufacturer. This information was originally only available to servicers via the Hitachi web site. I would not have posted it, however, if I had not found it elsewhere on the internet on sites that also post much mis-information regarding these repairs. It is my policy to repect the agreements with vendors like Hitachi regarding the distribution of their documents. Thus far, we have not received a response from requests to Hitachi regarding whether it is acceptable to post it, and since other sites have provided the information and it is supplied in each kit sold, we assume that the company is not concerned with its presence here.

 

Diagnosing the problem

Not all problems with convergence are the output ICs. Most certainly are, but before changing parts, or even buying them, you want to be sure. There are some symptoms that are pretty good indicators, but some problems are not so obvious. I will try to describe some of the ways that, as a technician, I would determine whether or not the output ICs are defective.

Symptoms can vary. The most common and obvious would be when the convergence cannot be corrected in one color in one direction. This indicates that one channel of one of the chips is likely bad. It could also mean that you simply have a bad solder connection at the IC, the connection to the yokes, a resistor, or a connection coming from the convergence generator. The first thing to do in diagnosis is to observe the symptoms carefully. Try adjusting the red and blue horizontally and vertically if you have manual controls or in the service menu. Try running any auto convergence mode if you have it and watch each color. If one does not move in one direction you have a good indication that one channel is bad or where to look for a bad connection.

Intermittent problems with convergence may indicate simply bad connections at the ICs. Some problems that are not intermittent can be the same. Check the solder joints for ring cracks. Many times the factory does not deposit enough solder on the pins and repeated heating and cooling cycles can cause the solder to crack.

Some sets may not even power up. It is not uncommon for shorted convergence outputs to cause a shutdown of the set and/or to blow fuses. It is always a good idea to look for the obvious, such as blown fuses, burned resistors, bad solder connections, etc. A lot of the process of troubleshooting is observing things that simply don't fit with a normally operating system. Checking power supplies is always a good start. There are usually a number of different power supply lines at different voltages supplying various circuits. The convergence supplies are almost always a pair of + and - supplies. If one of them is not coming up or goes down faster than the other, you have an important clue. When one of the supplies is down, if the set does run, convergence will usually be bad on all three colors, and in both directions.

If you suspect that convergence outputs are bad and causing a shutdown condition, one way to be sure is to disconnect the supply lines to the chips. It is sometimes easier just to remove the chips altogether. Nearly all sets will run with no convergence outputs. You won't get any convergence correction and the pix will be curved in on all sides and offset, but you should be able to measure the + and - supplies at that point to be sure that they are present. While the chips are out, you can also measure the output resistors that sometimes open when a chip fails. I'll deal more with those in another post.

While the chips are out, it is a good idea to check the dc offset at the six inputs to the ICs from the convergence generator circuit. If it is more than a few hundred millivolts, you need to deal with that. It could be that the position control has been adjusted to its limit trying to correct convergence, but it could also mean a problem in the circuits that generate the correction voltages. Some auto convergence systems will try to correct for a bad chip and end up with severe conditions driving the inputs. This can be difficult to deal with, but usually is correctable by running the convergence process as soon as the circuit is repaired.

Added note:
Many have posted with questions about fuses. Different sets have different types of fuses. Some use traditional glass fuses, some use pico fuses. Pico fuses are small resistor shaped devices that are soldered into the board. Many have labels on the board identifying them as fuses with the rating, some do not. They can be black, green, blue/green, yellow/orange or other colors, depending on the set. Refer to the service manual for each model for more info. As stated above, you should have positive and negative supply voltages at the output ICs and you can verify this with the chips removed with no damage to the set if everything else is OK. These supplies are usually in the 18-35 volt range, d.c.

Be Thorough!
Don't just assume that you have a convergence problem because colors don't line up. Verify that you cannot adjust it. If all of the adjustments for R,G,& B, both horizontal and vertical have an effect, your problem is somewhere other than the output ICs. You may have to go into the service mode to check this on some sets, but it is better to make a good diagnosis than to assume something and chase your tail. I have gone behind many other techs and consumers who jumped to a conclusion and wasted a lot of time changing parts only to have me later diagnose the problem as something else, like a pincushion problem or bad video processor IC causing a problem that affected the convergence.

Some sets allow you to reset the convergence and not store to memory, so that you can recover the convergencde memory if you find that you need to. Keep this in mind. A complete convergence reset can cause hours of work rebuilding the geometry and convergence, particularly if multiple modes are used for various formats and resolutions.

It is always a good idea to verify that there is no excessive offset from the convergence generator and that data is not corrupt before assuming you only have an output problem.

 

The Resistors

Added note:

If you have ANY DOUBT at all, CHANGE the resistors. Many techs and DIYers have blown ICs or confused themselves by missing an open resistor. Be sure that you check them after you remove the chips and after the convergence yoke connectors are disconnected. Some sets have resistors in parallel, so if you get a lower reading than you expect for a single resistor you need to take this into account. A bad resistor will read HIGHER resistance. If you have any doubt about the effect of the circuit on your reading, lift one leg and read the value out of the circuit.


If one has a problem with convergence circuits and simply assumes that changing the ICs will solve the problem, probably better than half of the time one would be correct. However, some sets have a tendency to damage related resistors when a chip fails. Sometimes, the resistors themselves will be the only problem. This is rare, and when it is the case, it is often because of an intermittent connection at the IC or an intermittent failure in the IC.

There are usually very low value resistors in series or parallel with the output and load. These are present to keep the chip from dumping more current than necessary and to equalize the impedance of the load resulting in more efficient operation and better linearity. The values are often somewhat critical. There are often more than one resistor in parallel to increase the power handling while using smaller and less costly parts. There are also usually resistors in parallel with the yoke. These are typically much higher values and lower power handling. Again, these are present to tune the circuit to operate more efficiently and with greater linearity. The better the design and choices of load resistors, for a given yoke/IC combination, the more predictable the convergence and likely greater adjustability.

WARNING: If you are not sure about the values of the reisistors or how to test them properly STOP. You can do more damage or damage new ICs if you don't get this right or miss an open resistor. Improper values can lead to alignment problems and overheating.

Some useful links for figuring out what values you have:
http://www.lalena.com/audio/electronics/color/
http://www.ealnet.com/m-eal/resistor/resistor.htm

It is very important to check the resistors when servicing these circuits. It is easiest to check them with a DMM with the chips removed and the yokes disconnected. Verify that they are the values marked on them, but remember, the circuit may affect the readings. In particular, the low value resistor s that are in parallel will not read their marked value. Look at the circuit to see how they are connected. If they are in parallel, two resistors will read half of the rated value. It is when you get a reading that is a higher ohm value that you have to be concerned. This means something is open or partially open. Resistors almost never fail by going lower in resistance. The go higher or to near infinity.

Even if they all measure properly, they need to be inspected carefully. If they are discolored differently from others in the circuit or have cracks or chips, they should be replaced. An open resistor can damage a new chip or just frustrate the out of you trying to adjust the set. Use flameproof or metal resistors in the same values as the originals unless the manufacturer suggests a change. They can normally be sourced from the same distributors that carry the chips.


When using the Hitachi kits, be sure to use the correct kit for your set and verify the values of the resistors in your set if you are not replacing them. Some sets require a change in the values to avoid a shutdown condition!

 

Heat

Dissipating heat is important for the reliability of output ICs in all sets that use them. Regardless of the set and the specifics of the circuit design, improper heat sinking can shorten the life of the outputs. It is important to clean off the old heat sink compound if it is dried. When applying new heat sink compound it is important to use only enough to fill the spaces where there is not metal to metal contact, but no more. More is NOT better.

I smear a thin layer on both surfaces, then slide the chips back and forth a bit until I feel metal scraping metal. This assures the best contact. To much heat sink compound actually inhibits the heat transfer to the heat sink. Heat sink compound is not a particularly good thermal conductor, but it is much better than air. You still want the metal to touch as much as possible. The Heat sink compound should just fill the spaces that don't touch.

Some sets are notorious for running very hot. Samsung sets that use the small board mounted on the CRT bulkhead are a good example. They may run hotter than most because the chips are higher in the set and subject to less cooling by convection. Some techs put fans on them. I have never done so and never had recalls of these repairs, so I do not think it is necessary. Extra cooling certainly can't hurt, but one should be very careful about installing any extra components in a set.

Another suggestion that may improve thermal transfer is milling the heat sink and back of the IC. I would be very careful with this procedure, with care not to remove significant metal from the IC. One way to do it is simply to place two layers of fine sandpaper back to back and slide it between the chip and the heat sink. This takes a bit off of the high points and can work well if a chip or the heat sink is not flat. I have rarely found it necessary, except on some smaller ICs and stamped heat sinks. These chips are usually mounted on larger heat sinks that are less likely to be warped.

Heat sink compound:

http://www.arcticsilver.com/#
http://www.gcelectronics.com/order/SubCatPDF/specialty chemicals 44 54 57-58.pdf
http://www.radioshack.com/product/i...=features&accessories=accessories&productId=2102858&support=support&tab=support
http://www.alliedelec.com/catalog/catalogpages/200607/1898.pdf?Catalog=&PageNum=1898

 

Soldering and Desoldering

If you have any soldering skill at all, most of these repairs are not difficult. The mistakes that I would expect most people to make are bridges between pins and damaging traces on the board. To minimize damage to the board, it is best to use an iron that is hot enough. A common misconception with regard to soldering is that to hot an iron will do more damage. This is only true in the extreme, as with butane powered irons or large soldering guns. Even these will not do damage unless they are applied too much. A hotter iron will get the job done faster, causing less heating of the component and the board. However, an iron that is too hot will cause oxidation which will make it harder to transfer heat. When this happens you can do damage by holding the iron on the joint too long. A good rule of thumb is if the tip stays shiny it is ready to use, if it gets dull or discolored the iron is too hot. A too hot iron will need frequent cleaning and tining.

For desoldering, a good choice is the radio shack desoldering iron with the red bulb. I works fine if you can get to the joints. Some chips will be mounted where they are hard to get to with such a large device. It is also fine to use de-soldering braid. Use a medium size and get a good quality braid. It should be shiny and not dull. Cut short pieces and hold them with a pair of pliers, and use a lot. Don't be stingy. Do not keep heating if it does not melt the solder rather quickly as you will likely damage the traces on the circuit board. When braid does not quickly pick up the solder, you either have too cool an iron or the braid is oxidized too much. Add some fresh solder to the joint or some liquid flux to the braid.

When soldering, I recommend using eutectic 63/37 lead solder. I use it on all boards, even those with lead free solder. It has a lower melting point and will lower the melting point of lead free solder when you add it to a joint. It is handy for desoldering on lead free boards, as they can be difficult to work with. You wont run into many lead free boards when working with convergence outputs but some have reduced lead contents and can be hard to desolder. Just add some fresh solder to a difficult joint and it will likely be easier to work with.

When reinstalling the chips, always secure the heat sink first, then solder the pins. This assures that there is no mechanical stress on the joint. Heat the pin and trace simultaneously and the solder should melt on the pin, not the iron. The rule of thumb for soldering is heat the work, not the solder. You should get a good flow and a smooth shiny joint. If not, the temperature is not right. Ideally, use a temperature controlled solder station. Otherwise, use a 40W-45W iron.

 

Adjusting Convergence

Once the repair is complete, the set will need some adjustment. There are so many different systems for adjusting convergence that it is not practical to describe them all here. This will be a very brief look at general issues. Specific information may be found in the vendor threads, or if you post a question in a new thread it is likely that we can give you some specific pointers.

Most sets never come from the factory converged as well as they could be. After changing convergence outputs, additional variance is likely to be introduced, from the new ICs themselves, which vary some, as well as any movement of wire placement or heat sink effectiveness changes. Resistor values may have changed, or resistance in the circuit may have been affected by soldering. Regardless, if you wan the most out of your set, tweak the convergence.

Some sets use some form of auto-convergence, with trade names such as flash focus, self focus, magic focus, or whatever. These may get you in the ballpark, but a close examination of the result will reveal that convergence errors still likely exist. This is because all of these systems use as a reference the last stored settings from the factory or the last time the set was manually converged. The "auto-convergence" is really just a reset to those values, using data from between four and eight sensors around the edge of the screen. You have to do the convergence manually then store it if you are going to get the best performance.

Generally, you will have to enter the service mode to get to the most effective level of convergence control. The method for doing so varies, so it is important to get the documentation for your set, if possible. Training and service manuals will usually have the details of negotiating the service menus. It is very important to only change things that you know you should be changing. Record your original data and your changes. Be certain about what you are doing because is is possible to do permanent, expensive, and in some cases, irreparable damage by altering service menu values on certain parameters.

It is not a good idea on most sets to try to reduce overscan by very much. You may just have to do a lot of re-convergence and geometry or you may miss the sensors on any auto-convergence systems. Check with someone familiar with the changes you want to make BEFORE making them.

Any focusing should be done before convergence adjustments.

Some terms that you may run into and the general order of adjustment on sytems that have these controls:

Static Convergence refers to the position of the whole image, vertically and horizontally.
Height and Width, aka size are pretty obvious.
Linearity refers to the relative size of different parts of the image, usually one side or the other or top to bottom.
Skew, aka Tilt refers to the angle of the lines relative to the edges of the screen, usually skew is on the vertical lines and tilt is on the horizontal lines.
Keystone, aka Trap refers to the relative size of each side or top and bottom. Incorrect keystone results in a trapezoid rather than a rectangle.
Pincushion refers to a bulging outward or barrel shaped distortion or the reverse, an hourglass shaped distortion where the sides bow inward.

The above controls may not be used on later sets with point convergence. Many systems use them as preliminary adjustments before point convergence, while some only have the individual point controls.

Be sure to understand how to save your settings and remember to do so before you quit. Also, be sure that you understand how to initialize the data for any auto-convergence functions. Some sets will not behave properly if this is not done.


What if the ICs and resistors do not fix the problem?
First, look for the obvious. A connector may not be plugged in or may be loose, you may have bridged a solder joint of have a solder drip or splash somewhere it shouldn't be, or you may have missed an open resistor or fuse. Check for bad solder connections on related regulators and other circuits. Moving a board around can upset connections that you may not have noticed. Check the controls...what works and what does not. Do you have + and - supplies to the output ICs? Do you have correction signals coming from the convergence generator (this takes a scope to see) and do they change when adjusting? What is the DC offset at the inputs to the convergence amps? As a last resort, try a full convergence reset if your set has it, but understand that you may have to start from scratch and need a reference grid to get it corrected. If the problem is not a botched repair or misplaced connector (which most are), you could have a problem with a bad EEPROM, convergence yoke, or convergence generator. These problems will often require a professional to troubleshoot.

One thing to do if you are continuing to blow fuses or have shutdown problems is remove the ICs and replace the fuses. You can safely run nearly any set with no convergence amp ICs installed. If the set runs, you know it probably has to do with the converence amps or related circuits. You may have missed a resistor or had a bad connection, or blew a chip with a solder bridge or with residual voltage in the circuit. You may also have a problem somewhere else or a problem with the power supply. Sometimes with bad caps in the supplies you can get some unusual problems, so the filter caps on the convergence supplies should be checked.

 

Repair Cost

These repairs are so common that they deserve some breakout treatment and discussion of what one should expect from a servicer. There are lots of folks who can DIY these repairs, and lots who should not or would not attempt it themselves. For those who choose to have a technician perform the repair, it may be useful to get the perpective of a servicer. A lot of techs might not like some of the opinion here, but that's life.

Rates will vary greatly for most repairs. Shops in different areas have very different costs of doing business. I will give my general rates below, but keep in mind that they are likely quite low compared to other areas with higher costs of doing business. That said, a lot of shops really put the screws to customers on these repairs. High rates, sub-par replacement parts, not doing research, and lack of careful alignment have been seen in the work of many shops. I will describe what we do to give an idea of what a consumer should be looking for. I have little patience for shops that do not perform work with professionalism and who are not thorough.

Most convergence repairs can be done in the home if the tech is prepared. One should know the model number of the set, research the common repairs, have the likely output ICs, fuses, and resistors, and be prepared to complete most repairs in one trip. Some may turn out to be more complex and require a return trip or shop repair, but changing convergence outputs and related repairs should be rather routine. That said, one should understand that not every problem that involves convergence is going to be a simple matter of replacing output ICs. I generally allocate 2-3 hours including local travel to give plenty of time to do most jobs right. A less experienced tech should probably allocate 3-4 hours.

My charges are broken down into the categories of service call charge, labor, and parts. The service call charge is a flat rate for the trip out, diagnosis and providing an estimate. The labor is for the on site reapair, and the parts charge includes the chips, resistors, fuses, and a standard materials charge to cover things like solder, wick, heat sink compound, cleaners, freeze spray, etc.

A service call is priced by zip code, starting at $75 for the most local areas. Labor for most convergence output replacements is $150-225, depending on the set and specifics of the problem. We charge $37.50 each for most output ICs, $2.00 for most fuses, and $3.00 for most resistors, and $4.00 for materials. A typical repair would, therefore, cost from $300 to $375, plus tax IF I WAS DOING IT LOCALLY. Rates much higher than this would be reasonable in some markets, but with sloppy or less thorough service would, IMO, be a poor value.

All repairs should include the following and my techs are expected to (provide):
Prepare for the job BEFORE leaving the shop by doing necessary research to perform the job efficiently.
Arrive on time per scheduled appointments.
Diagnosis.
Parts replacement with the most updated part appropriate for the set using only original OEM parts.
Thorough cleaning of the heat sink and proper application of new heat sink compound.
Solder left looking as good or better than original factory work.
Cleaning of excess flux residue.
Resoldering other areas in the set known to create problems such as regulators or vertical ICs.
Carefully re-dressing wires in original manner.
Cleaning screens, lenses and mirrors with safe and effective products.
Optical, mechanical, electrostatic, and/or magnetic focusing as possible and necessary.
Visual gray scale adjustment.
Better than factory convergence adjustment in almost all cases.
A.C. leakage test for safety.
Grounding check.
Basic user level adjustment of the picture.
System evealuation and recommendations for improved wiring, wire management, system design, surge suppression, etc.
90 day warranty on repairs.

This is just the view of one service manager, though it is based on experience going back to 1979 and hundreds of these kinds of repairs, along with communication with dozens of other dealers, techs and shops on a regular basis.

 

Re: Repair Cost

Hi,

First of all, thank you for your very informative narritave on convergence problems with RPTV's as well as source material and options for repair.

I am experiencing the red & blue convergence problems (green is perfect) you described with my Mitsubishi WT-42311. In looking for replacement IC's STK392-110, I have serched this site's suppliers for your recommended replacement, STK394-160, but have not been able to find a source to buy them. Do you know where I can find a good quality STK394-160? I have found STK392-110, 150, AND 180 but not much luck with the STK394-160. They all should be a good match for my Mits CRT RPTV set right?

Thanks for your help,

gewiz44

 

You can get the STK394-160 in the Hitachi kits mentioned above, available through the Hitachi distributors such as Tritronics and Andrews.

 

Terrific Article Thanks

 

lcaillo,

Thank you so much for your hard work on this as this information will prove to be very helpful to many of us who have CRT RPTVs
So far my Sony has worked flawlessly but I suspect it wont be forever.

:T

 

Re: The chips

Hi,

I fixed my Mitsubishi WT-42311 using the information supplied in this thread, thanks. I tried to get the STK394-160's but because of problems with ordering and time, I settled for the STK392-150 IC's. I bought the solder sucker from radio shack ($11.00) and it worked like a charm. It's the one that is heated and has a squeeze bulb attached. After removing the old IC's I used a small screw driver to scribe around the old IC's onto the heat sink. That gave me a close placement guide for the new IC's to line up with the solder points on the circuit board. Then I spread a thin layer of new thermal compound on the back of each new IC and positioned them on the heat sink. It still took 4 - 5 tries to thread the 36 leads through the appropriate holes in the circuit board. My heat sink has holes to anchor through the circuit board into the TV chasis. I used small bolts to hold the heat sink to the circuit board for soldering. I applied flux to the leads and terimals and carefully soldered with a 45watt iron. Afterwards, I used a tooth brush to carefully clean flux and residue from between the terminals and checked with a magnifing glass to be sure nothing was bridging between any of the termanals. I then removed the bolts and carefully reinstalled the circuit board double and triple checking connections. I held my breath and turned on the power and it came on close to converged. After warming up I converged the set for both cable and component imputs and I noticed how hot the IC's were so I got a computer chip fan and attached it where it would blow on the chips and heat sink just to be safe. I used a cheap plug in transformer for it's power supply (12VDC) but I am thinking I could tap off of a transformer in the power supply of the TV for the fan (with a fuse in line) since it only draws .07 amps. It has a great picture and I am a happy camper.

Thanks again

 

While the 12 volt supply might be able to handle the extra load, for safety reasons I would recommend not trying it. You also may get some noise feeding back into the video or audio circuits from the fan. Just keep using the wall wart.

 

Just wanted to say thanks lcaillo, for all your time to put this thread together , I was very nearly caught up in the extorsion that my local repair guy (Gold Coast, Australia) was about to inflict on me.

He would not even look at the set unless I let him pick it up, and that was $110 ,whilst the repair would start at $300 on top of that. He had no phone credit to return my calls , and I dont think I would have put my dog in his van , let alone my 134cm.:wits-end:

So feeling helpless, and after sneakily finding out what and where the convergence board was, I came up with the STK392-120 chip number , entered it in the google search , and well here we are.

Cut a long story short, In australia I cant buy these IC's any cheaper than $130 each+ freight, so after buying them online from "Electronic Repair Kits" in Canada (Got 2 Pairs ,1 Pair For later) They arrived in 4 days and cost $5 air freight, which was cheaper than the freight in my own country. Also the IC's cost me $15 each as opposed to $130 each over here.:T

So after following clear instuctions, that I found on the net.

http://home.earthlink.net/~oleg.filippov/ConvergenceFix.htm

And then proudly turning the TV on, in front of the "astonished" Wife and Kids , Im glad to say if I wasent a legend in their eyes before ,I certainly am Now ! (thanks to you):hail:

So one question before I wind it up?

I have noticed the 2 big heat sinks on my IC board, Getting very hot.

( by the way my TV is an LG PT53A83T ), ,

So much so that I can only hold my hand on them for a matter of seconds before getting to hot to touch.
This cant be good , and after reading the thread and any other thread I can find on this , Was wondering is this normal ?

I noticed one Gentleman in this thread putting a PC chip fan , on his heatsinks which seems like a great idea , however wouldn't he have to keep turning the tranformer on and off with the TV, Or can you get them that only turn on with the sencing of heat ??????

Any advise is appreciated, and once again thankyou for your great thread.

Kind Regards Marty. :bigsmile:

 

I also wanted to thank you for taking the time to write this lengthy post. I have been doing research on fixing a Hitachi 43UWX10B with a suspected convergence problem. I have quickly examined the board and don't see any obvious cooked resistors, but i will test them when the new chips come hopefully at the end of this week. I did extensive reading and found that Hitachi replaced the STK392-110's with the aforementioned 394-160's, which i have ordered. I bought them here if it's any help to people, http://bestbuy.partsearch.com/Part/Hitachi+Ltd/Hitachi/CZ01341/New.aspx, i also bought tools from www.electronix.com. i don't know much about either site, but Bestbuy seems reputable, and the only reason i went with Electronix is because it came up first with Google and had everything in a pretty good layout. Hopefully they were good decisions, i'll keep you posted on my progress and thank the Home Theater Shack and it's mods for excellent, informational, forums.

 

Thank you for the kind words. The parts from Best Buy appear to be originals, but the price is kind of high. I buy them in the Hitachi kit for a lower price. Electronix is a no go for semiconductors. For tools, etc, they are ok. The semiconductors that they sell are often cheap copies and not original Sanyo parts.

 

OK, all my parts and tools will be here tomorrow in time for the weekend. My last question is if anyone knows the resistors that typically go bad when the IC's cook. I see they're all marked on the board, but didn't know if someone could narrow down the possibilities for me, as I will probably test some of them to see if any may be bad. Again, thanks for all the help.

 

Look in the Resistors post above. More spcific tips would require some extra research or studying the schematic of your particular circuit.

 

Thanks for the input. I will continue to use the "wall wart" it is easier that way too. The TV has been working flawlessly. I'm as happy as a bug in warm poop.

 

OK. took the board out and seem to have a blown resistor. can i run the tv for a short and not cook the new ic's till i get a new resistor, or not good idea?

 

Never run any product with a known bad part, especially a convergence circuit with even one bad resistor. They are there for a reason and it is very possible to cause more problems.

 

Thanks to all the great info I was able to swap out the original convergence chips for aPT53W53G with 2 new -150's and everything works like new. All of your advice and comments were spot on.

 

OK folks, here's the scoop. I changed out the convergence chips on my 43UWX10B from STK392-110's to the new Hitachi STK394-160's. I also ended up swapping out the RK50 resistor, a 2.2ohm 1W, metal oxide resistor. The first run was a tough one. The screen was completely FUBAR'd and I thought all hope was lost. The blue was so far out I thought it would never come back. On top of things, my son and I began to smell something burning, and upon inspection behind the TV noticed the RK50 was glowing cherry red. I immediately unplugged the TV and was gonna give up. I had an extinguisher nearby, and said "screw it, i'm going for it". 20 minutes later in the DCAM and it actually looked really good. I was definately impressed with the picture, it seemed to be just fine. I unplugged the TV and metered the resistor, it was now cool and metered to 3ohms, outside the 5% tolerance of the 2.2. I attributed the bad resistor to the new convergence chips and the TV being so far out of whack. Luckily, I bought two, replaced it again, now with no glowing sensation, ran DCAM again, ran magic focus a couple times, and all seems to be extremely well. I am very happy with the picture, and the high-def kicks A@#! I want to thank all of you again for your help, and I hope I don't need it, but if I do, I'll know where to look. :whew:

 

lcaillo, you rock!
Thanks for your time and sharing your knowledge. As a newbie I learned 2 tings. First, I'm probably going to pay someone with experience to do the repair (don't want to burn down the house). Second, the tech I had originally called for a quote is a bum! He quoted $600 and wasn't a fraction the professional you are. Thanks for your help!