More on "Super Dog" Curtis Mathes/Samsung TV model CM27001S

Hi,

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.

I hope one of you had a similar experience with this brand of TV.

Thanks in advance, Brad

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Reply to
Brad
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Is the 2nd anode volts supposed to be 27kv?

Reply to
Meat Plow

Hi Meat Plow,

Boy, I forgot to say in all the details, that the 27KV is within specs.

To answer your question, yes, 27KV is within specs.

However, if you have read and remembered what I said, you would realize that excessive HV is not the cause of this problem. "WIth the screen turned all the way down, the TV stays on". Maybe not my exact words, but it should be close. Brad

Reply to
Brad

I remember what you mentioned but though 27kv was a bit too much. You have any way to check the CRT?

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Reply to
Meat Plow

snipped-for-privacy@verizon.net (Brad) wrote in news: snipped-for-privacy@news.verizon.net:

Have you found where the shutdown is coming from ?

Some circuit fault is causing the shutdown...

Have you checked to see if the micro is being reset ?

I don't have a diagram, but have you tried adding a little more damping capacitance across the HOT C-E junction and see if that makes a difference.

R!

Reply to
R!

Hi R!,

I put the set aside for now. I already put too much time in on this TV. If I ever fix it, I promise I will let everyone know via "Update: ...." (new post).

I know you are all trying to be helpful with all your suggestions, but I would LOVE to get a reply from someone who had the same problem, and that person tells me/us what he/she did to fix it.

Brad

Reply to
Brad

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