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Discussion Starter #1
I would like some guidance in an initial diagnosis on a problem that has just started on my Toshiba 55H70 set. After the set has been on for a few hours, the image begins to shrink and expand in a jerky fashion. It appears to be more in the horizontal direction, but I can detect some vertical change when it is extreme, as in came in a few inches on the sides. All of the colors are moving at about the same rate. When the image is the most compressed I can see some alignment issues, but it is much less than the overall movement. I could usually get it to stop by unplugging the tv and letting it sit for a bit then plugging it back in and powering up. About half the time it came right up when powered on, but sometimes the power led would begin to flash in a slow pattern. Today it added some occasional horizontal lines of black in the image, and no longer powers up running good for any length of time.

My initial thought was this was some sort of power supply issue, but after reading this forum I am not so sure anymore. I do have the service manual and schematics, though I have never needed them to this point.

Up until a week ago, this tv set was very reliable, only occasionally needing tweeking of the basic alignment. I value how this set supports the 4:3 ratio in the big screen, but also supports 1080i HD via component input for a great high def picture.

Thanks for any suggestions.
 

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If the problem is mostly in width and somewhat less in the vertical, I would guess power supply as well. It could be other things, including the hyper module problems that are common in these sets, but that usually has other symptoms such as jagged distortions or loss of sync.

If it is only present after the set has been on for a long while, the problem is likely identifiable with thermal changes. When it starts you can try freeze spray on suspected parts, but be careful not to use too much, as it creates condensation that can cause shorts. You might also have a bad solder connection that is opening up with heat.
 

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Discussion Starter #3
Thank you for your reply, now for the terminology lesson. What would jagged distortions or loss of sync look like? As the problem got worse on my set the sides did become jagged and distorted.

I am taking the TV down from it's alcove this afternoon and will try to get into it this evening to start looking at the solder joints and such. I will also look for burned resistors or suspect caps. I'll get some freeze spray tomorrow.
 

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I have removed the board with the convergence chips and heatsink on it for closer inspection. It is a pretty large bard with a lot of other circuitry on it and hard soldered RF sheilds containing circuitry. Getting to the ic's will not be easy if required. I've already started wondering how I will remove the screw when I only have an inch of space before the next shielded board.

I have looked over the board and didn't find any obvious burn marks or even anything that looked like it had gotten hot. The dust on the large resistors all looks the same. I have looked carefully at all the solder work and don't see anything resembling a cold-solder joint or ring fracture. All looks good. I haven't removed the power and high voltage board but from an observation from the back I don't see anything burned there either. I'm going to get some batteries for my flashlight so I can see more detail, particularly when I do remove and flip the board over in the chassis to look for solder problems.

I hope I'm not stumped on this one.
 

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Your post was moved to he proper manufacturer forum to maintain forum organization to make information easier to find.

Loss of sync would look like an old tv with horizontal and vertical hold controls that were out of adjustment. Horizontal sync problems result in a pix that is distorted in a diagonal manner and/or shifted sideways, vertical sync problems result in a rolling image. If you have jagged distortion, you likely have the problem with the caps in the hyper module. It is the shielded board just behind the input panel. Toshiba recommends replacing all of the 10uF and 22uF polar electrolytic caps in that module. I have found that there are usually others that are going bad also. You can either replace them all or use an ESR meter to find the bad ones.

These modules also sometimes have bad solder connections on the crystals (oscillators).
 

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Discussion Starter #6
It sounds like it might be the hyper module given the descriptions you gave. At this point the set will no longer power up. It goes directly to the blinking power led after a few seconds. Would a hyper board failure manifest itself like this, starting with a bit of a problem the progressing through the loss of horizontal sync to power on failure? Is the self test detecting the problem having gotten worse or has another problem occurred? Thanks for any guidance you can share.
 

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Generally the hyper module will not cause shutdown. Most likely you disturbed some weak solder connections and blew a convergence IC and a fuse. I never do a hyper module without doing the convergence ICs for this reason. The solder joints are weak to start with and the chips are just waiting to fail. For the relatively low cost of the chips I just go ahead and change them while in the set in most cases.
 

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Discussion Starter #8
Thanks for the info. I thought that was the way I needed to go. I found a tech who will do the cap replacements on the hyper card for me as I don't really want to mess with surface mount stuff. I am going to replace the convergence chips as well as review the resistors in the surrounding circuit. I think i may also just reflow the solder on all joints I can find. I understand I should order a stk394-160e hitachi kit, plus any required resistors and fuses, correct? Is there a particular hitachi kit recommended? Also, how do I recognize the fuses that I should look for as having been blown? And will the fuses be in the vicinity of the convergence circuits or do I need to backtrack through the power board as well?

I did print out the schematics and they do a good job of giving me some of the expected voltages in particular places on the board, including the convergence chip pins. Getting a probe to reach then is going to be a trick, but that is what late nights are for, right?

I hope I am on the right track here...
 

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Fuses test as an open circuit when blown, or as a short when intact. I would suggest that you resolder everthing and check the fuses and resistors, then verify that you have the other problems fixed before ordering parts. You can run the set with the ICs removed, and you should have a normal image but with no convergence correction.

Some have reported incompatability of the -160 ICs in some Toshiba sets. I have not run into it, but suggest that you consider replacing with the original parts to be safe. If you do decide to order a Hitachi kit, it makes no difference which one, as the resistors will not be correct for your Toshiba anyway.
 

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Discussion Starter #10
I removed the convergence chips and checked the resistors around them. They are all fine. A local tech came and said it wasn't the hyperboard and pointed me back at the convergence chips, suggesting removing them and seeing then if the set powers on. Otherwise we have to go back through the power board as you indicated. I am ordering the STK394-250A's from Acme as they were recommended as the replacement device for the 110.
 

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I don't know who made that recommendation, but I do not. When there are problems that you don't know the source of, why would you complicate the matter by subbing parts. Stick with the original STK392-110.
 

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Discussion Starter #12
OK, I will get the -110's. It was a Sanyo publication that listed the -250 as the replacement. I wish I had known better how to remove the chips before I went through all the trouble of removing the board in front of them. Taking the chips and the heatsinks at the same time was much easier. I have put the other board back and resoldered the case. I have resoldered about half of the board so far. My eyes can only take so much in a stretch before I start to fade and make mistakes.

I should be able to power this up without the chips and look for all the correct voltages, right? If I don't find one that is specified then I should start working back through the supplies? While waiting on the chips I want to look at everything else.
 

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Where did you see a Sanyo pub on this sub? I would like to get a copy of it.

Yes, you can run the set without the chips.
 

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Discussion Starter #14
Well, I can't get the system to run without going into the protect mode. I see the power come up on all the supplies then immediately shut down. Nothing will power up if I disconnect the signal converter board. All of the fuses I could find on the schematic and on the board are good. There are a few solder joints that look suspect on the power board that I will be working on tomorrow. Maybe they are causing the fault. I have the convergence chips removed so they shouldn't be shutting it down. If I don't have any luck tomorrow after some resoldering, I think I'm going to have to get a pro to do some diagnostics. I haven't found any instructions on how to isolate the power board and jumper the protection circuit to verify proper operation, so I can't determine which board is the problem. I also a bit frustrated that I can't find any of the test points I see on the board listed on the schematic. This is frustrating and disappointing. Any suggestions on how to proceed would be appreciated.

My biggest concern now about bringing in a pro will be dealing with the questions about my troubleshooting/meddling in the system. Hopefully that won't drive the price up.
 

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I would explain everyting you have done very carefully. Going behind someone to sort out what they did can be very difficult. It completely changes the assumptions that you can make about where a problem might be. You have to look for things that otherwise would not be a concern. This is one of the risks of DIY repairs. It can easily increase the cost above what you may have paid without going into the set. Many techs will not even take such jobs because they can waste so much time and the client is usually unwilling to pay for the time that it takes to sort out a mess.

It is generally unwise to "jumper" proection circuits to find what is causing them to operate. This can result in damage to more components. Chances are that you missed something in re-assembly, bridged a couple of solder joints or damaged something in handling.
 

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Discussion Starter #16
I haven't posted in a while and wanted to bring this thread up to date...

I called in a service tech recently and explained my situation. He was not offended at the work I had already done and didn't treat me with disrespect, so I was pretty happy with that from the start. He set out to diagnose the power up problem first, which turned out to be some bad solder connections on the power supply board. Once he resolved that problem the jittery horizontal image size was still present. He began looking into that, going through a number of possible issues including an arcing yoke. In the end it turned out to leaked coolant fluid on the power supply board causing the supply voltages to fluctuate as the fluid warmed up. He cleaned the affected are, then recommended I install a drip shield to prevent a recurrence. Total cost for 2.5 hours of diagnostics was a bit over $200.
 

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Did he wash the board in solvent? If not, I'd be removing it and giving it a good wash in alcohol, followed by running it through the dishwasher.

Coolant leaks are very rare on Toshibas. I have never seen one The coolant is a 70/30 mix of ethylene glycol and glycerine. It is not conductive itself. It does absorb moisture out of the air and dissolves residue and debris on the board to form a very effective electrolyte. It then corrodes leads on components and creates shorts. It could certainly vary with temperature, but it sounds more like some caps breaking down to me. I would be wary of this diagnosis and watch for more problems...
 

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Discussion Starter #18
Aw, man! Why you have to go bringing me down with these negative waves? And my TV got wind of them and decided to start acting up this evening too. What a bummer.

The jittery horizontal image is back, but only very slightly. I also am hearing what sounds like arcing from the power pcb in the area of the multi-tap transformer. I have used a hollow tube to try and localize the arcing and it appears to be loudest from the transformer itself. The pcb does look like it needs to be cleaned as there is a lot of white residue on the surface. On the solder side there is a fair amount of flux residue as well.

The tech told me he found the coolant leak drops while he was soldering on the board. I was watching him go through the process of desoldering and checking the caps. He told me he smelled the coolant fluid burning when he started working in a particular area.

As to the arcing sound on the pcb, would that be caused by bad caps causing the transformer to be in some distress, or is it possible the transformer itself is problematic?

I have alcohol, a brush, and spray flux remover/pcb cleaner I can use to clean the pcb when it is time to do so. I was a bit surprised by the suggestion to put the board in the dishwasher though. How do I assure the water is clear of the inductors when it comes out? What cycle and type of soap if any should I use?
 

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Arcing from the FBT is likely a lead not seated properly or the transformer itself bad. Most often the former if the boards were moved.

I wash the boards in alcohol and run them through the dishwasher. The detergent is not critical, but a good rinse and dry is. One of the advantages of the dishwasher is the dry cycle. It is hard to get a board dry after washing. I learned of the method from a tech who workd for Tektronix, the test equipment maker. There is nothing harmful about water nor most detergents (some do contain chlorine bleach but not enough to be a problem with a god rinse with just water).

Like I said, the diagnosis seems very odd. Never seen coolant leak on one of these at all. My guess is that he saw some residual silicone grease that leached out from heat sink compound or the residue from leaky caps.
 

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Discussion Starter #20
I don't think it is the flyback transformer. My limited understanding is the flyback is the large phenolic encased high voltage transformer. The one I am referring to is the multi-tap power transformer that that feeds the control circuits. I have experienced noisy transformers in the past responding to downstream load conditions, but this does seem awfully noisy. And it definitely is in sync with the screen distortions as far as time and volume relative to the extent of the distortion. I am also getting some crackling out of the speakers when the transformer is noisy.

Any ideas on where I should go? I cleaned the board in the area and it looks very good. I have thought about starting to remove the caps and looking at them out of circuit for problems.
 
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