Re: Tough "Dog", Curtis Mathes/Samsung TV model CM27001S

Hi,

In response to your replies, I did check caps for high ESR on the chance
that when the picture begins to show, a "load" is placed on the regulated
B+.

When the picture begins to show, a "load" is added to the HV trippler
and FBT. Is it possible this "load" causes a "breakdown" in FBT?
Note: I don't see evidence of this on the scope as I advance the "screen".

I thought about making a HV "dummy" load to substitute for the picture tube
as a test, but I don't know what the current is (normal brightness current).

If I fix this "DOG", I will post an "Update".

Brad


On Sat, 16 Jun 2007 18:58:46 GMT, in sci.electronics.repair you wrote:

Hi,

I have a Curtis Mathes/Samsung TV model CM27001S (mfg. 11/01) in my
shop. I now have SM (.PDF file)

The TV will turn on. There is around 27KV (measured) for the CRT. There
is vertical deflection and good sound, but just as the picture begins to show,
the TV turns off. Note: This happens every time you turn on the TV.

Note: Regulated B+ is 130V (measured).

I unplugged the CRT pcb and the TV stays on. I plugged it back onto the
CRT and turn "screen" (FBT) to minimum. I turn on the TV and it says on, but
when I turn up the "screen" slowly, just as the picture begins to show, TV
turns off. Note: I tested the CRT and it is AOK. If I turn the "screen" all
the way up, then turn on the TV, I can see a good picture just for moment,
but the TV turns off. I scoped FBT with "screen" turned all the way down.
Very good FB pulses which doesn't change at the point the TV turns off
(by advancing the "screen"). The "Xray" circuit is not the cause (tested).
I put a "pull up" (via bias box) on the ABL line to "hold up" the voltage
which would drop (viewed on scope) at the moment the picture starts to show,
but the TV still turns off.

Did you have one of these sets with the same symptom? What
caused it?

Thanks in advance, Brad

Before you type your password, credit card number, etc.,
be sure there is no active keystroke logger (spyware) in your PC.

.

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