Poor vertical linearity (Toshiba 2100TD)

[dfahren]

Hi there,

I'd like to know which parts of my television (Toshiba 2100TD) might cause the following symptoms:
The picture shows poor vertical linearity. That means in the middle of the screen the picture seems normal, at the bottom some lines moved out of the screen but the worst is the top where many lines seem to be lost, for example you can't see the first line of the teletext display any more.
Can you give me any hints as to what parts need to be replaced?
A year ago, I had my tv set repaired by some "technician". Issue was the same. Now it seems the parts don't have a long lifetime. Do you know what must be done in order to extend the lifetime of those parts?

Thanks in advance!

Cheers, Dietrich

P.S.: Sorry for my english, I'm german.

[Guest]

Hi, you have bad electrolytic caps in the vertical circuit, usually
replacing ALL the defective ones will cause the set to run reliably
for 4-5 years, obviously the tech missed one that was on the way
out, you may also have poor solder connections on the vertical
output IC, Larry E

[dfahren]

Hi Larry,

thanks for the answer. Can you tell me how I can spot those defective caps? I mean, when I open the case they all look pretty the same to me.
There is no sign of escaped electrolyte or something like that. Sure the ones that have been renewed have no dust, but having dust doesn't mean they are defective, ain't it?
Ok, I will also check the solder connections of the vert. output IC. Let me clarify which is the IC you mean. Is it the AN5515, the driver IC, or do you think of the TA8659AN, the big one with the 64 pins?

Dietrich

[Guest]

Dietrich, I`m in USA so I don`t recognize the model number the
vertical IC will be 6-7 pins probably the AN you quoted, it will be
attatched to a metal heatsink, not knowing that model I can`t tell
you which caps are actually bad, they are usually 1uf @ 50 or 2.2uf
@50volts and marked C301, C305 (at least here in the states) you
might be better off to take it to a tech, remember that electrolytic
caps are polarized, which means theres a positive pin and a negative pin
don`t reverse them, (pay attention when you remove them) again you
would be better off having a tech repair this good luck, Larry E

[Guest]

Hi!

Sorry, I'm from Hungary, and my English is very bad.
Unfortunetly I have the same problem. My TV is a Toshiba 2112DD.
The type of the V.out IC: LA7837. May be the firma use analog parts for this function.
I foolow the tips from Larry and find a capacitor C331 1uf @ 63V on the IC pin 6.
The near of the V.out IC I found only this capacitor with a big capacity. The other electrolyt caps are 220 uf and 68 uf.

On the next week I take a new 1uf cap and change it.
I hope, it's suceed...

Tibor

[Guest]

Hey guys, your english is great as far as I`m concerned, One thing
I forgot to mention is the color of the capacitor is usually different
from all the rest (if they have never been changed) in most of the sets I have repaired the bad caps were red or brown and all the other caps
in the vertical area were black or dark blue, as I said before usually
marked 1uf at 50 volts or 2.2 at 50 volts, yours may be 63 volts because I think you guys use 220 volts at the outlet, we use 110 volts in the states
here it`s usually capacitors C301, C305, C342, C308 good luck
Larry Eastman
American TV & Electronics
Crystal River, FL. USA

[dfahren]

Hi there Larry and Tibor,

last night I repaired my Toshiba. Larry, you are completely right, the defective cap was a brown one. Its name is C303, has 2.2uF with 50V, which might be too little for our 230 Volts. So I replaced it with a 2.2uF with 63V. The new capacitor didn't have a mark I know for the minus pin. So I tried it both ways. Guess what happend ... Yep, the TV shot down the instant I switched it on. Not very amusing. But Toshiba builds its TV sets with a TDA4601 that switches off the TV when it notices something is going wrong. (At least I think it's working that way.) So I resoldered the cap and, yep, my TV is up and running again and is working like a new one! That was great!
Sure, Larry, if my TV set had had more severe problems like some IC is defective or some special component had needed to be changed, I would have given it to some technician. But since I needed to change just one cap, I decided to do this on my own because last time I paid for this more than $130 (110 Euro) and then I would have invested more than $200 in a TV set that has no stereo, no up-to-date HF-tuner and the like.
Tibor, your Toshiba 2112DD seems to work differently than my Toshiba 2100TD. At least the circuit diagrams look pretty different. And I also think the way the vertical deflection is controlled in your TV is done differently than in mine. So I can't give you any hint as to which cap(s) you should change. Unfortunately, the circuit diagram you can download from this Web site has pretty poor quality. You can't even read the characters properly. 8-(
Nevertheless, when looking at the diagram, I can see four caps I think you should replace. These are 3300uF, 25V near the vertical position switch, the 1uF next to it (Voltage??), the 220uF (35V??) which connects to pin 8 of the LA7837, and finally and particularly the 47uF (10V??) which connects to pin 1 and pin 5 (via the 10K resistor) of the LA7837.
My recommendation is, first, replace one cap then check if the TV set is still working, then replace the next one and so on until you are done.
One last remark: It might be necessary to desolder (correct word?) one or more metal plates on the back of the board to get to the caps. Please also keep in mind, there are voltages up to 25KV in your TV set that can kill humans! At any rate unplug your TV set from electricity and make sure you wait a bit before you start to solder some component so that remaining charge can dissipate from caps.
I hope you will also get your TV set working back soon!!!!

Cheers, Dietrich

[dfahren]

Larry,
maybe you can also help me on this one ....
I notice that the width of my TV picture has become wider in the last year. Maybe it's also a capacitor problem, maybe not, I don't know. Unfortunately, my Toshiba 2100TD only has a potentiometer that, when turned, affects the position of the complete picture on the screen. So turning this potentiometer shifts either shifts the picture a bit to the left or to the right. I would like to know if there is some resistor that can be replaced by a potentiometer so that I can change the width of the picture.
Thanks for you help. It's always highly appreciated!

Cheers, Dietrich

[Guest]

I do not agree with Dfarhen, if you do not know what you are doing or do not have a tester for the capacitors, change all of them that are near the chips heatsink. (they are only a few cents each) Make sure the new ones are all high temperature (105 degrees C) Lean them away from the heatsink before soldering and do not get them too hot.
An electrolytic charged in reverse will explode (did you hear a pop?) Now the electrolyte can leak out. I would replace it.
Some verticle heatsinks get very hot. On these, mounting the capacitor underneath the board may help.
Some cheap/older televisions are built with 85 DegreeC capacitors. If yours is like this have you considered replacing them all? You can do this for about half the cost of an ESR tester.

[Guest]

Dietrich, this ones a little harder, check solder connections in and around the horizontal output transistor, resolder horizontal driver transformer,
(check with bright light and magnifying glass), if solder is good, replace the cap(s) off the collector of the horizontal output transistor, one side of
the cap will go to the collector the other side to the emitter (or ground)
these caps are usually not electrolytics but are generally low value
high voltage mylars, not polarized, (you can put them in either way)
good luck, Larry E