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Toshiba 2939db vertical problem Fixed but new problem!!!   Goto page 1, 2  Next  
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bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Fri May 29, 2009 9:00 am    Post subject: Toshiba 2939db vertical problem Fixed but new problem!!! Reply with quote

To be honest I can't remember the TV's model number now so I'll have to post that when I've been home again but the outline of the problem is that I have a Toshiba (approx 28" & 2000 vintage) CRT lump which has compressed the vertical right down to about 4mm in the middle of the screen, occasionally flickering to fullscreen for a split-second now & again.

I know I really need to post the model/chassis etc & I'll get those ASAP but for now if there's a common problem that would cause this symptom I'd much appreciate a few pointers as to what it could be.

Nice post on CRT discharge by the way, I've had a few zaps in my idiot youth using the "unplug it and let it sit for a day" method & it ain't nice. Always used to surprise me though, the amount of TV's that were fixable simply by cleaning the PCB and maybe resoldering a dry joint or two. Hopefully I'll be able to do something with this one as it's a bit nicer than my current Beko effort & has surround sound built in to drown out the sound of next doors awful "boom chaboom chaboom cha wawawa" excuse that they call music...

Hopefully I can get online tomorrow with more specific details of the TV.

Cheers, Dan.


Last edited by bikermack on Fri Jun 05, 2009 7:45 am; edited 1 time in total
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bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Fri May 29, 2009 9:21 am    Post subject: Reply with quote

Well I've just had a search round & it does appear to be a fairly common Toshiba problem, so I'll have a look tonight and resolder the vertical I/C and check the values of the caps. If I get no joy there I'll post up the model number etc & see if anyone has any other ideas...
kuhurdler



Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Fri May 29, 2009 9:32 am    Post subject: Reply with quote

the fix you are looking for is probably very similar to this one:
http://www.riddledtv.com/repair/journal/Vertical/
bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Sat May 30, 2009 8:52 am    Post subject: Reply with quote

Looks like I could be in luck, under magnification the vertical I/C joints appear to be cracked (backed up by the fact that I noticed the jumping to full screen was affected by tapping the side of the case). All I've gotta do now is find the small iron & I'm away.
I'll call back in here after I have a go at it & let you know how it goes.

Cheers, Dan..
bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Thu Jun 04, 2009 9:29 am    Post subject: Reply with quote

Right, I've had a look and it's a 2939db model. I had a go at resoldering the vertical IC the other night & to be honest I'm not sure it's the joints on that now, unless I'm getting dry joints every time, because after about 7 attempts it's still not playing ball. (Fairly sure I'm going after the right chip, it's the only one with 7 pins & is marked as IC301...)

Is there anything else that could need retouching with the iron while I'm in there, or is it more likely to be the capacitors or the chip itself that's dead?

Cheers, Dan.

EDIT-: meant to say, I also noticed that when there's no vertical the line across the screen is tilted about 10 degrees anticlockwise, and when it flickers it sometimes looks just fine & other times there's a lot of horizontal distortion (it kind of looks like when you degauss an old pc monitor). Don't know if that means anything?...
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kuhurdler



Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Thu Jun 04, 2009 9:39 am    Post subject: Reply with quote

I'd probably try to replace that chip then, and any electrolytic capacitors close by.
bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Thu Jun 04, 2009 9:54 am    Post subject: Reply with quote

Alright thanks, One thing I will try before biting the bullet is to firstly dig out my multimeter (I know it's somewhere!!!) and then make a brew and just sit & buzz from the IC pins out to make sure nothing's still open circuit around the general area...

Oh, silly question probably, but would I be able to use the vertical IC from a different size set? I have access to numerous scrap sets, generally dropped stuff with smashed tubes or wrecked boards although none are as big as this (largest probably 20"). I guess it's just as cheap & easy to just buy the part but if anything else would do that'd be great as I'm completely broke now due to my CX500's affinity for eating exhausts...
kuhurdler



Joined: 28 Dec 2006
Posts: 2879
Location: Overland Park, KS

PostPosted: Thu Jun 04, 2009 10:00 am    Post subject: Reply with quote

sure, you can salvage parts. Just match the designation from your existing Vert IC chip. maybe LA78xx?
I probably wouldn't recommend reuse of capacitors, because they're pretty cheap.
bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Thu Jun 04, 2009 10:07 am    Post subject: Reply with quote

Yeah caps are always best new IMO, to be honest I think the IC's only fitted to toshiba sets from the listings on wehaveparts-: Ta8427k (sets 24w10st thru tv35d90).

Thanks for the speedy replies, much more encouraging than some other sites I could mention... Cool

Cheers, Dan.

EDIT-: actually, there is an equivalent chip fitted to Sharp sets (RH-IX1224CEZZ) so I'll have a look see if I have one lying about. A new one's only $5 anyhow so no biggie if I have to buy one. Thanks again.
bikermack



Joined: 29 May 2009
Posts: 23
Location: Crewe

PostPosted: Fri Jun 05, 2009 7:43 am    Post subject: Fixed!!! :) Reply with quote

Right, I've managed to cure the vertical deflection problem on this set. The reason I didn't spot the fault straight off was mainly due to laziness (I didn't bother to remove the board from the chassis) and turns out to be caused by a previous repair being rushed.
When the board was screwed back onto the chassis it wasn't clipped in properly & they snapped one corner off, fortunately the damage was limited to one track (link from flyback terminal through t461 to c445). Soldering a jumper wire between the break resulted in a very nice looking picture although there is another fault possibly linked to the previous work someone did.

Basically what I have now is a perfect picture, albeit tilted about 10 degrees anticlockwise. Would this be as simple a fix as I hope, i.e. slacken the clamp on the CRT gun & rotate it until the picture is level, or is it more involved than that? I have a feeling I'm going to be into the service menu to sort this properly but would appreciate any input.

Another problem is the surround outputs & bass tube are not working but that could be a setup issue & Sky's remote setup doesn't allow menu access so I'll leave this issue until I have the proper remote. Any suggestions on the former issue would be much appreciated.
Many thanks, Dan.


Last edited by bikermack on Sat Jun 06, 2009 7:52 am; edited 1 time in total
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