Toshiba CF27E50 squashed vert

"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

... :

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...

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

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

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

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

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?

Adam