Toshiba 2877DB - Int. frame collapse

[M.Joshi]

Hello,

We own a Toshiba 2877DB television which has recently developed an
intermittent horizontal frame collapse problem.

A while back, I noticed a feint white line bouncing at the bottom of
the screen.

About a week ago, it developed the frame collapse problem. I checked
for dry solder joints around the H. Output transistor (Q404) and also
re-soldered some of the connections in the horizontal output section
that looked dull.

The TV subsequently worked for a few days but then the same problem
again. I have re-soldered the connections to the LOPT and some other
components in the horizontal output section area. Unfortunately, the
problem is now worse!

I have searched for common fixes but nothing comes up that is relevant
for the TV. Some sites mention a frame IC (TA1241) needing to be
replaced for this model however, I couldn't locate it on the
schematic?

I'm wondering if one of the capacitors may have dried up?

I have uploaded the schematic to the following site, hoping that
someone can offer some advice:

http://tinyurl.com/owzkku

Thanks.




--
M.Joshi

 

[Mark Zacharias]

"M.Joshi" <M.Joshi.45179fb@diybanter.com> wrote in message
news:M.Joshi.45179fb@diybanter.com...

Hello,

We own a Toshiba 2877DB television which has recently developed an
intermittent horizontal frame collapse problem.

A while back, I noticed a feint white line bouncing at the bottom of
the screen.

About a week ago, it developed the frame collapse problem. I checked
for dry solder joints around the H. Output transistor (Q404) and also
re-soldered some of the connections in the horizontal output section
that looked dull.

The TV subsequently worked for a few days but then the same problem
again. I have re-soldered the connections to the LOPT and some other
components in the horizontal output section area. Unfortunately, the
problem is now worse!

I have searched for common fixes but nothing comes up that is relevant
for the TV. Some sites mention a frame IC (TA1241) needing to be
replaced for this model however, I couldn't locate it on the
schematic?

I'm wondering if one of the capacitors may have dried up?

I have uploaded the schematic to the following site, hoping that
someone can offer some advice:

http://tinyurl.com/owzkku

Thanks.




--
M.Joshi

Obviously, the vertical output IC needs to be resoldered, as well as the
yoke connector plug at the main board. The IC, probably the TA1241 you
mentioned, will resemble a small audio amp IC on a heat sink, not too far
from the yoke plug.

Additionally, Toshibas are notorious for bad capacitors in and relating to
the vertical section.


Mark Z.

 

[Franc Zabkar]

On Thu, 14 May 2009 01:51:10 +0100, M.Joshi
<M.Joshi.45179fb@diybanter.com> put finger to keyboard and composed:

We own a Toshiba 2877DB television which has recently developed an
intermittent horizontal frame collapse problem.

A while back, I noticed a feint white line bouncing at the bottom of
the screen.

About a week ago, it developed the frame collapse problem. I checked
for dry solder joints around the H. Output transistor (Q404) and also
re-soldered some of the connections in the horizontal output section
that looked dull.

You should be checking the vertical section, not the horizontal.

I have uploaded the schematic to the following site, hoping that
someone can offer some advice:

http://tinyurl.com/owzkku

Check frame IC Q301 (TA8427K) for dry solder joints. Also check R305.
Replace the electrolytic capacitors in that area.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[M.Joshi]

Update:

I replaced a couple of the small-value electrolytic capacitors around
the frame output IC Q301 (TA8427K):

C320 (100ľF)
C305 (1ľF)

I also re-made some of the solder joints in that area.

The TV worked OK for a day with the white horizontal line still
bouncing at the bottom of the screen. However, it has the
frame-collapse problem again. Tapping the TV recovers it!

I will try re-soldering the frame output IC and coil connections.




--
M.Joshi