Toshiba CF27E50 squashed vert
 

Hello all, I acquired a Toshiba CF27E50 tv that seems to have a problem
with the vertical. The picture is squashed about 2 inches below the top
of the screen.

I ordered the schematics and service info from Sams and checked all the
voltages on the TA8427K vert amp chip and they were ok. The service info
said to replace 4 caps which I did (but with pulls from scrap). So their
condition may be questionable.

Is it worth looking at anything with a scope or should I just replace
the TA8427K and all the caps in the surrounding area? Thanks.


Adam

Replace the associated electrolytic capacitors in the vertical deflection
circuit, especially recd or green case. ESR all of them!
"Adam Stouffer" wrote in message
news:XMowe.2024$At6.1953@trndny09...
Hello all, I acquired a Toshiba CF27E50 tv that seems to have a problem
with the vertical. The picture is squashed about 2 inches below the top of
the screen.

I ordered the schematics and service info from Sams and checked all the
voltages on the TA8427K vert amp chip and they were ok. The service info
said to replace 4 caps which I did (but with pulls from scrap). So their
condition may be questionable.

Is it worth looking at anything with a scope or should I just replace the
TA8427K and all the caps in the surrounding area? Thanks.


Adam

"Adam Stouffer" bravely wrote to "All" (29 Jun 05 03:42:47)
--- on the heady topic of "Toshiba CF27E50 squashed vert"

AS From: Adam Stouffer
AS Xref: aeinews sci.electronics.repair:51856

AS Hello all, I acquired a Toshiba CF27E50 tv that seems to have a
AS problem with the vertical. The picture is squashed about 2 inches
AS below the top of the screen.

AS I ordered the schematics and service info from Sams and checked all
AS the voltages on the TA8427K vert amp chip and they were ok. The
AS service info said to replace 4 caps which I did (but with pulls from
AS scrap). So their condition may be questionable.

AS Is it worth looking at anything with a scope or should I just replace
AS the TA8427K and all the caps in the surrounding area? Thanks.


Adam,

There is often a rectifier diode associated with the pump-up circuit.
It may have gone high resistance and should be replaced along with all
the electros around the vert-ic. Also check for the proper supply
voltages. If the fbk derived vertical supply is low this could also be
caused by a high resistance recitifer, bad filter electro, or high
value dropping resistor. Inspect the yoke plug for good solder.

A*s*i*m*o*v

.... :) What does that wire do? =8Q (oh!)

Asimov wrote:

Adam,

There is often a rectifier diode associated with the pump-up circuit.
It may have gone high resistance and should be replaced along with all
the electros around the vert-ic. Also check for the proper supply
voltages. If the fbk derived vertical supply is low this could also be
caused by a high resistance recitifer, bad filter electro, or high
value dropping resistor. Inspect the yoke plug for good solder.

I replaced the 3 diodes and noticed a slight improvement. So it looks
like I'm on the right track. Still going to order a new vert chip
because its only $3. Are normal high temp caps ok or would low ESR caps
be a better choice? Thanks again.


Adam

"Adam Stouffer" ha scritto nel messaggio
news:y0Jwe.14160$Q27.4746@trndny02...

because its only $3. Are normal high temp caps ok or would low ESR caps
be a better choice? Thanks again.

If the circuit didn't include LOW-ESR caps why did you want to insert them ?
Use normal 105° caps !!!

I.

Hi there are two capacitors that fail in these sets, cant remember the
values,however one is in the frame sync circuit it goes o/c and there is
another in the deflection circuit also. They are quite low value and easily
identified by being a different colour to the rest. They are a red/brown
colour.They fail in 99% of cases.
Tom


="Adam Stouffer" wrote in message
news:XMowe.2024$At6.1953@trndny09...
Hello all, I acquired a Toshiba CF27E50 tv that seems to have a problem
with the vertical. The picture is squashed about 2 inches below the top of
the screen.

I ordered the schematics and service info from Sams and checked all the
voltages on the TA8427K vert amp chip and they were ok. The service info
said to replace 4 caps which I did (but with pulls from scrap). So their
condition may be questionable.

Is it worth looking at anything with a scope or should I just replace the
TA8427K and all the caps in the surrounding area? Thanks.


Adam

Hi, I remember there are a red cap locating other place of verit circuit.

"Adam Stouffer" wrote in message
news:XMowe.2024$At6.1953@trndny09...
Hello all, I acquired a Toshiba CF27E50 tv that seems to have a problem
with the vertical. The picture is squashed about 2 inches below the top
of the screen.

I ordered the schematics and service info from Sams and checked all the
voltages on the TA8427K vert amp chip and they were ok. The service info
said to replace 4 caps which I did (but with pulls from scrap). So their
condition may be questionable.

Is it worth looking at anything with a scope or should I just replace
the TA8427K and all the caps in the surrounding area? Thanks.


Adam

On Wed, 29 Jun 2005 03:42:47 GMT, Adam Stouffer
put finger to keyboard and composed:

Hello all, I acquired a Toshiba CF27E50 tv that seems to have a problem
with the vertical. The picture is squashed about 2 inches below the top
of the screen.

I ordered the schematics and service info from Sams and checked all the
voltages on the TA8427K vert amp chip and they were ok. The service info
said to replace 4 caps which I did (but with pulls from scrap). So their
condition may be questionable.

Is it worth looking at anything with a scope or should I just replace
the TA8427K and all the caps in the surrounding area? Thanks.

FWIW, some Toshiba models have a small electro cap near the jungle IC
(TA8718N) that causes the same symptoms. IIRC, it's about 2.2uF 50V.


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

james wrote:
Hi there are two capacitors that fail in these sets, cant remember the
values,however one is in the frame sync circuit it goes o/c and there is
another in the deflection circuit also. They are quite low value and easily
identified by being a different colour to the rest. They are a red/brown
colour.They fail in 99% of cases.
Tom

Well I replaced the TA8427K, 3 diodes, and a number of caps. All the
caps connected to the vert amp chip and the feedback circuit were
replaced. I replaced every 2.2uf cap because those were most commonly
mentioned as going bad.

The vertical is still squashed and tends to flicker up and down
slightly. There are no red 'lytic caps anywhere on the board. Most are
blue or black with a few teal making up the rest. The only red caps are
film. Should I be looking at some of those or is it time to break out
the scope?

Others have mentioned doing an ESR test of every cap but I don't have an
ESR meter available. Is the signal gen/scope method worth trying?
http://www.fullnet.com/u/tomg/esrscope.htm Any help appreciated.


Adam