samsung t200hd won't power up

[selldoor]

Re: samsung t200hd won't power up

Hi - Happy Christmas - Just re read your query re Cold/secondary and have deleted my thoughts. Also this may help with the SMPS-controller http://www.fairchildsemi.com/sitesea...itemap+id&ia=1

[jananas]

Re: samsung t200hd won't power up

The replacement cap is an axial cap. Got it from a television repare store in the village where I live in. Do you imply there's a fundamental difference in composition between axial and radial capacitors other than the position of the poles?

The original cap gave 0.0 Vdc, so does the new one.

[jananas]

Re: samsung t200hd won't power up

@selldoor:

Thanks for the warning Already did so and after I unplugged the board I wait some time and then short all the caps with a screwdriver to make sure I don't get a jolt. This wouldn't damage the capacitors would it?

[retiredcaps]

Re: samsung t200hd won't power up

D201C: 0.178V out of range
D201B: 0.178V out of range
D201A: 0.178V out of range

The above are all good.

D202,

1(+) - 2(-): 0,208V ..................... 1(-) - 2(+): out of range
2(+) - 3(-): out of range .............. 2(-) - 3(+): 0,207 V
1(+) - 3(-): 0,001V ......................1(-) - 3(+): 0,001V

When you see a diode like this -><-, that is really two diodes in one physical package. The readings that matter are 1-2, 2-1 and 2-3, 3-2.

D202 is good.

Quick question about terminology: Do you mean by secondary side, the cold site?

Yes. Also known as B+ sometimes.

[retiredcaps]

Re: samsung t200hd won't power up

Also this may help with the SMPS-controller http://www.fairchildsemi.com/sitesea...itemap+id&ia=1

If you refer to



page 3 will have the pinouts. Notice the notch or dot will indicate pin 1.

Pin 4 is GND and pin 6 is Vcc. Measure the resistance between these 2 pins. Set your multimeter on 200 ohms scale.

[retiredcaps]

Re: samsung t200hd won't power up

Got it from a television repare store in the village where I live in.

A SMPS application requires low ESR caps.

See post #19, section 1

https://www.badcaps.net/forum/showpo...4&postcount=19

[retiredcaps]

Re: samsung t200hd won't power up

IF the SMPS pin 4 and 6 are NOT shorted, then desolder ZD101 and retest out of circuit. If it is indeed shorted, that is likely the problem.

[retiredcaps]

Re: samsung t200hd won't power up

ZD101 is definitely shorted.

Otherwise, the voltage could be inferred from the SMPS controller.

Page 13 has a parts list for the Typical Application Circuit (page 11).

ZD101 is listed as a Fairchild 1N4744.

[retiredcaps]

Re: samsung t200hd won't power up

then short all the caps with a screwdriver

Most modern electronics will have some sort of bleeder resistor that discharges the caps after a minute or two.

You can also verify that a large capacitor is discharged by measuring the DC voltage across the legs. A discharged capacitor will read close to 0.0 V DC.

If you have to discharge a capacitor, see

http://www.repairfaq.org/REPAIR/F_sm...ml#SMPSFAQ_019

[selldoor]

Re: samsung t200hd won't power up

@selldoor:

Thanks for the warning Already did so and after I unplugged the board I wait some time and then short all the caps with a screwdriver to make sure I don't get a jolt. This wouldn't damage the capacitors would it?

I am just learning myself but a Senior Member Longbow said this a few weeks back:A good rule of thumb is to never use a screwdriver to discharge a capacitor. This method can damage the cap very easily and it will take a bite out of the screwdriver. The larger the uF value, the more like a welder the cap can be. Have a convenient 100 ohm 5 watt resistor handy for discharging caps. For tube equipment you can use a 1K resistor due to higher voltages. Put probes on the resistor if you want.

[jananas]

Re: samsung t200hd won't power up

If you have to discharge a capacitor, see

http://www.repairfaq.org/REPAIR/F_sm...ml#SMPSFAQ_019

I'll keep that one in mind.

Just tested the smps-controller.

1.2 ohms--> I would say not shorted, correct?

[retiredcaps]

Re: samsung t200hd won't power up

Just tested the smps-controller.

1.2 ohms--> I would say not shorted, correct?

Those readings suggest the SMPS is shorted. However, it could be because ZD101 is shorted and causing the readings on the SMPS to appear shorted.

To find out for sure, do the following.

1) Remove (desolder) ZD101 because it is way easier to do than the SMPS controller.

2) Retest ZD101 with your diode function. Report findings.

3) With ZD101 out of the board now, re-measure the resistance between pin 4 to pin 6. Report findings.

[retiredcaps]

Re: samsung t200hd won't power up

Just to make sure we are measuring the correct SMPS pins, I marked pins 4 and 6.

[jananas]

Re: samsung t200hd won't power up

Ok, I desoldered ZD101.

New measurements:
SMPS-controller: pin 4-pin 6: 36.2 Ohms
ZD101: 0,001V - 0,002V

Looks like the problem is located than. I'll try to get an replacement and update.

Do diodes die from non-specific causes or should I look for an ultimate cause of the diode becoming shorted?

[selldoor]

Re: samsung t200hd won't power up

Just out of interest I think this is the same board as in the 933HD see "SAMSUNG 933HD exploded" I have looked at the electrotanya schematics for both models but they dont seem to have any info on the IP Board.

[retiredcaps]

Re: samsung t200hd won't power up

SMPS-controller: pin 4-pin 6: 36.2 Ohms
ZD101: 0,001V - 0,002V

Do diodes die from non-specific causes or should I look for an ultimate cause of the diode becoming shorted?

See if the diode has any markings to indicate it might be a 1N4744.

The pin 4 to pin 6 is still a bit low, but let's assume it is good for now.

The diode may have blown from you shorting out the board. Sometimes they die of age and use.

[retiredcaps]

Re: samsung t200hd won't power up

Just out of interest I think this is the same board as in the 933HD see "SAMSUNG 933HD exploded"

Wow, I don't remember that board from 11 months ago. Good eye to spot that.

[jananas]

Re: samsung t200hd won't power up

Happy new year,

Here's an update of the last week.

Finally got to an electronics store in the neighbourhood to get the zenerdiode replacement. I printed out the specifications-sheet from fairchild and gave it to him. He told me he had it in store and gave me a 15W zenerdiode.

Measurements after soldering it in:

Secondary (output) Voltages --> all 0
Voltage over the start-up cap --> 0

Resistance over the start-up cap -->36.2 Ohms
Resistance over the SMPS-controller --> 36.2 Ohms (pin 4-pin 6)

Wondering why it still didn't work I looked up the diode again and saw that it should be 1/4W.

Multiplying the Nominal Zener voltage with the Iz Test Current from the specifications I gave too the shopowner:

15 [V] * 17 [mA] = 0.255 W

I can imagine this is a reason why it wouldnt work. Will try to get a new one and doublecheck if I got a shop-owner who knows what he is talking about.

Kind regards,

Jan