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"Super Dog", Curtis Mathes/Samsung TV model CM27001S, additions

B

Brad

Jan 1, 1970
0
Hi,

Since my previous post (see below), I had performed a few more tests,
including a picture tube substitute. Someone (I found via Google) had a
similar case in 2003. He replaced the FBTas a last resort, and gave up.
Note: I was unable to contact this person.

Please, will someone who had a similar experience with this brand of TV,
tell me what you did to fix it..

Thanks Very Much in advance, Brad

PS, I promise, if I fix this "Super Dog", I will post an "Update:" so
everyone will know what caused this problem.
-------------------------------------------------------------------------------------------------------
PREVIOUS "SUPER DOG" POST:

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

I have updated this from my original post and added more information.

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). Caps have low ESR. A 200 ohm
dummy load on +130V doesn't cause voltage to drop at all.

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. 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 opened the ABL line and put a 10K resistor from the FBT ABL pin to
ground. The ABL line, now isolated, will be unaffected by FBT/HV trippler
"effects". The ABL circuit has a 79K resistor to regulated B+ and a 6.8K
resistor to ground which will keep the voltage constant on the now isolated
ABL line. With "screen" turned all the way down, the TV stays on. As I
slowly advance the "screen", I see a good quality picture for a split second,
then the TV turns off.

I disconnected the HV lead from CRT and isolated it so no arcs occur.
This in effect, removes a "load" (when picture shows) on the HV trippler/FBT.
The TV still turns off.

I opened up the screen circuit on the CRT PCB and used an external
adjustable power supply to supply the screen voltage to G2 in the CRT on a
chance that if G2 shorts, it wouldn't "effect" shut down, but the blasted TV
still turns off. I am just about ready to give up.
 
R

R!

Jan 1, 1970
0
[email protected] (Brad) wrote in
Hi,

Since my previous post (see below), I had performed a few more
tests,
including a picture tube substitute. Someone (I found via Google) had
a similar case in 2003. He replaced the FBTas a last resort, and gave
up. Note: I was unable to contact this person.

Please, will someone who had a similar experience with this brand
of TV,
tell me what you did to fix it..

Thanks Very Much in advance, Brad

PS, I promise, if I fix this "Super Dog", I will post an "Update:"
so everyone will know what caused this problem.
---------------------------------------------------------------------- -
--------------------------------
PREVIOUS "SUPER DOG" POST:

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

I have updated this from my original post and added more
information.

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). Caps have low ESR. A 200
ohm
dummy load on +130V doesn't cause voltage to drop at all.

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. 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 opened the ABL line and put a 10K resistor from the FBT ABL pin
to
ground. The ABL line, now isolated, will be unaffected by FBT/HV
trippler "effects". The ABL circuit has a 79K resistor to regulated
B+ and a 6.8K resistor to ground which will keep the voltage constant
on the now isolated ABL line. With "screen" turned all the way down,
the TV stays on. As I slowly advance the "screen", I see a good
quality picture for a split second, then the TV turns off.

I disconnected the HV lead from CRT and isolated it so no arcs
occur.
This in effect, removes a "load" (when picture shows) on the HV
trippler/FBT. The TV still turns off.

I opened up the screen circuit on the CRT PCB and used an external
adjustable power supply to supply the screen voltage to G2 in the CRT
on a chance that if G2 shorts, it wouldn't "effect" shut down, but the
blasted TV still turns off. I am just about ready to give up.

Do you have a "print" to this set ?

Just junk the darn thing, if you don't...

R!
 
M

Matt J. McCullar

Jan 1, 1970
0
Can you swap out the horizontal output transistor and/or the flyback/tripler
assembly to isolate the problem? It sounds like something is breaking down
under load.
 
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