Philips TV model 20PT6245/37, Vertical Deflection Problem
 

Hi Bob,

I should have said in my "update", I didn't list all the tests I
performed.

There is no coupling capacitor to the yoke in this TV.

For now, I put the "DOG" aside so I can work on other "stuff".

Brad

On Thu, 6 Nov 2008 18:05:56 -0800 (PST), in sci.electronics.repair you wrote:

On Nov 6, 8:20*am, (Brad) wrote:
Hi,

* * *Here is an update, but TV is not repaired yet:

* * *Note: *TV chassis is L03.1UAA and I have SM.

* * *The vertical deflection system uses discreet components.
There is no vertical amplifier IC, *which is common in all other TVs
I have worked on. *I replaced "2463" 100/50 and "2446" 470/16.
Both measured a loss of capacitance, but it made no improvement.
"2465" 10/160 tested very good, however I replaced it, but it didn't
fix the problem.

* * *I tested the two output transistors out of circuit (AOK). *I tested other
transistors in circuit. *Also tested various components in the vertical
deflection circuits. * Note: I originally checked solder joints and soldered
several joints that seem to lack good solder bond.

* * *I used a Yoke tester and checked both windings individually
after I separated the windings at a terminal. * Both windings read
"good", but one winding had a *higher reading than the other. *I
repeated the test incase of a poor test lead(s) connection, but the results
were the same!

* * Scoping the two inputs to the vertical amp, *the "+drive" signal doesn't
match "-drive" waveform, *although it's "inverted". *The +drive signal is
"abnormal".
* * * * * * * * * * * * * * * * Brad



On Thu, 23 Oct 2008 11:42:33 GMT, Brad wrote:
Hi,

* * I bought the service manual and found out that AN7225N is not the
vertical IC.

* * If I repair this TV (in my spare time), *I will let everyone know what
part(s) caused this problem.

* * * * * * * * * * Brad

On Thu, 23 Oct 2008 11:42:33 GMT, *Brad wrote:

Hi,

* I have a Philips TV model 20PT6245/37 (mfg 05/05) in my
service shop with a loss of vertical deflection. *I do not have SM.

*For a moment after the TV is turned on, there is some vertical deflection,
but it collapsed into a single horizontal line in the middle.

* I checked solder joints at the vertical IC, resoldered them anyway, but
this had no effect. *Note: I soldered other joints too. *Flexing and tapping
on mother board has no effect.

* I couldn't find pin out info on the vertical IC * AN7225N on the
web so I could make additional tests.

* * * * * * *Thanks in advance, *Brad

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If you have a scope, it and a dc voltmeter, you should be able to
check the voltages on the output transistors to make sure they are
biased correctly and then check the waveforms. If you don't see any
sawtooth at the output of the pair of output transistors, that's your
problem. If you do have a sawtooth there, then maybe the capactior
coupleing the output to the deflection coils is open/

Bob Hofmann