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Toshiba 50H72 has NO sound or Pic after STK392 Replaced

 
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Balram
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PostPosted: Fri Apr 01, 2005 12:24 pm    Post subject: Toshiba 50H72 has NO sound or Pic after STK392 Replaced Reply with quote

Hi,

This TV is 2-1/2 years old and last month the convergence problem made me replace the 2 STK329-110 IC's that fixed the problem. Now again the problem was the same but littel more then before. The convergence was very bad and my family members had to see it, so after a while with all the poor convergence where you could hardly make out any thing, suddenly the picture and sound just went off though the red pilot light in the front was still switched ON.
I have replaced the STK's again and checked all the registors but the situation is still the same. No picture and no sound.

Can any expert help me on this?

Thanks,

Balram
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gutenberg
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PostPosted: Wed Apr 06, 2005 10:25 pm    Post subject: 50H72 Reply with quote

Join the club. My 50H72 is also 2-1/2 years old, and twice it has blown its deflector board. Symptom = no picture or sound, but power LED stays on. I'm fighting with Best Buy right now about it. Very curious how many other 50H72's have the same problem and if they should be recalled.
E-mail me at [email protected] to compare our problems further[/i]
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mark



Joined: 20 Jan 2005
Posts: 43

PostPosted: Thu Apr 07, 2005 12:03 am    Post subject: Reply with quote

check the pico fuses on the power/deflection board. they may have opened up.
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Balram
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PostPosted: Thu Apr 28, 2005 1:10 am    Post subject: Reply with quote

Thanks Mark, You were right. The two 5 Amp and One 2 Amp were also blown. Replaced and at least got the screen. But, now with the same Convergence issue. Would you say the STK's have gone bad again?

Thanks,
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mark



Joined: 20 Jan 2005
Posts: 43

PostPosted: Thu May 05, 2005 5:12 am    Post subject: Reply with quote

if you used cheap amps, probably.
make sure the picos didnt just open back up again.

when you work on a convergence circuit in a toshiba, or any other for that matter always verify the values of the power resistors. if any of these resistors have changed value or
opened up your gunna kill the new amps or have weird convergence problems.

most of the time, if its changed value you end up with weirdness.
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Balram
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PostPosted: Tue May 10, 2005 7:31 pm    Post subject: Reply with quote

Hi Mark,

Thanks for your advice. I checked all the power resistors for the value and replaced the 2 STKs again.
Things are still the same. Now, let me tell you the out put in the convergence mode.
The convergence is all equally separated. (Red, Blue & Green), all are identically wiggly in shape (Vertical & Horizontal). We can see the Digital matrix for few seconds that comes up when 7 is pressed on the remote to save the convergence. (This is fine too). Though separated, (Which is also normal) it also shows the matrix when we press 1 on the remote after bringing up the designers mode to load from the backup data. The result remains the same even after this backup data is uploaded.

I am still wondering if the Digital Convergence Unit has been affected and need to be replaced. Any idea about the cost? Your tips on further diagnostics would be much appreciated.

Thanks again,
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mark



Joined: 20 Jan 2005
Posts: 43

PostPosted: Wed May 11, 2005 2:24 am    Post subject: Reply with quote

ok, so since you know how to get into service mode and convergence alignment...
my question is, can you move any of the 3 colors at all?

you would go in, using 2,4,6,8 buttons to move your cursor and 5 to set your location, 3 to chance colors.

if you can move all 3 colors horizontally and vertically...
you probably dont have an amp problem but you lost your convergence data.
I have seen it happen altho rare.

if you still cannot move your colors its time for a scope, and look at the amp inputs to see if your dcu is outputting correction signal.
but, as a substitute, if you have power at the convergence ics (BOTH rails, +/-30v)
and, the resistors are good...
your amps are probably ok. they dont fail in any spectacle.
now, if you still cant move a color you may have a defunct dcu. the dcu in toshibas does go bad, so do hypher boards.

anyhow...
if you can move the colors, either in service mode or normal customer convergence that eliminates the amps, pretty much.
if it does not _SAVE_ where you set the lines to, and this does happen!
your eeprom in the dcu has gone bad, or the dcu itself has gone bad.
I would try the eeprom first. if its a no-go replace the dcu but you will need a template or a duplicate eeprom from another set, to get you close enough to cope with it.

try this stuff out and see what happens.
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Balram
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PostPosted: Thu May 12, 2005 9:20 am    Post subject: Reply with quote

Hi Mark,

Thats a very logical approach. Yes! I can move each color line and save it too. Horizontal movement is more than the vertical. I dont think that they can really be moved so much so enough to overlap each other. The lines are too fare apart and to try it at all points .will be a nightmare too. I would guess the DCU. What do you think? I dont have a scope but if you think I might still need it, I can arrange one for some time. I had tried to run a Processor diagnostics by hitting 9 on the remote in the designer mode. All looks good between the IC links.

Thanks for your continues great help.
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