HannsG HH241 problems

[Dougmeister]

It's been awhile since I tested it, but it seems to me that it would work for a while, then power off.

Here are some screenshots of the capacitors.

I tried testing the caps still on the board using the digital multimeter "trick" (set to Ohms, charge the caps a bit, then switch the multimeter to "volts" and see if the numbers slowly decrease). I know the test isn't foolproof, but it says all the caps are still good.

I don't see any major leakage or swelling in the tops of the caps. I've only ever fixed one LCD monitor before and that was the problem.

Could it be the power supply or something other than the capacitors? What should I do next?

Thanks.

Pic 1
Pic 2
Pic 3
Pic 4
Pic 5
Pic 6
Pic 7

[budm]

Re: HannsG HH241 problems

You need to monitor the voltages, usually 5V for the main board, and voltage (14~17V) for the backlights inverter when it is working and when it is not working. Is this really 24" monitor? Pretty small power supply-inverter for 24"

[Agent24]

Re: HannsG HH241 problems

I tried testing the caps still on the board using the digital multimeter "trick" (set to Ohms, charge the caps a bit, then switch the multimeter to "volts" and see if the numbers slowly decrease). I know the test isn't foolproof, but it says all the caps are still good.

You can find open\shorted capacitors that way, but that's about it. Unfortunately you will not find out if they have high ESR or low capacitance, which is what really matters in this kind of situation.

Yes it could well be something other than the capacitors. Bad lamps or some problem with their wiring, or inverter problem, all can cause random shutdowns.

Try what budm suggested, to start with.

[Dougmeister]

Re: HannsG HH241 problems

You need to monitor the voltages, usually 5V for the main board, and voltage (14~17V) for the backlights inverter when it is working and when it is not working. Is this really 24" monitor? Pretty small power supply-inverter for 24"

Can someone point me in the right direction as to how to test these voltages?
* 5V for the main board, and
* voltage (14~17V) for the backlights inverter

I don't know where to put the leads of the multimeter. Thanks.

Edit: I guess the first link in Bud's signature would be a good place to start?
"Basic LCD TV and Monitor troubleshooting guides"?

[Zomalaja]

Re: HannsG HH241 problems

I have an HH241 that did that same thing, turn on then go blank - my caps were bulging a little. I replaced them but also replaced the dual diode SRF 1020 as well as the 10 Ohm resistor. I see in picture #5 that the board is discolored just as mine was. The part I used was a Taiwan Semiconductor SRF 1020, 10A, 20V, Dual Schottky Rectifier, Isolated. They had no stock so I had to wait for a sample from overseas, but it's working fine now.

[Dougmeister]

Re: HannsG HH241 problems

I have not been able to get the bulbs, etc. needed to test the power supply and main board, so I'd like to just replace all the capacitors.

Can someone help me figure out which caps to order and from where? I guess I should order the SRF 1020 and the 10 Ohm resistor while I'm at it...

[Davi.p]

Re: HannsG HH241 problems

Dougmeister you better make some measurements before order parts if don't want to trash time and money, from pic 3 i see one of the 2 double diodes on heatsink that seems not connected well to heatsink, to test the outputs simply switch on the board, even with video board disconnected, set tester in volt, place the red probe to the center pin of the 2 double diodes on h.sink , the black prb to the h.sink or a board screw.
Zomalaja: i don't see discoloration. When you turned on before fixing it showed the image?

The most important thing: do you see a status led lit after the mon. stop working? Remain same colour?

[Dougmeister]

Re: HannsG HH241 problems

Nothing like bringing a thread back to life after a year and a half...

I *finally* am making time to get back to this project.

Where exactly is the heat sink in photo #3?

[budm]

Re: HannsG HH241 problems

"Where exactly is the heat sink in photo #3?"
http://jdw10.com/pics/3.jpg

There are three heatsinks, I do not understand what you are asking.

[Dougmeister]

Re: HannsG HH241 problems

Sorry. I was responding to this comment above:

"from pic 3 i see one of the 2 double diodes on heatsink that seems not connected well to heatsink,"

Where are the diodes that aren't connected well to one of the heatsinks?

[Dougmeister]

Re: HannsG HH241 problems

Can someone please point out the heatsink that has the double diode not connected correctly?

[vinceroger69]

Re: HannsG HH241 problems

top left diode the bottom edge does not look like its touching the heatsink maybe just the picture but if you zoom in on it you will see yourself.

[Xcat2008]

Re: HannsG HH241 problems

Dont know if this will Help.. but i had my Samsung T190 with the same or similar symptoms...

Sometimes work's good for Hours, some times 5 mn and Turn off.. And sometimes never turn on and only after few Switch on and Off get it working.. So open it up, and had some capacitors damaged... So i have replace them all.. And is still working for about 3 years

So i hould suggest you maybe replace all the Capacitors since they are cheap... or maybe check in the back of the board if you have Broken Solder...

Sometimes the problem is smiling for us, and we cannot see it hehe

Good luck

[Agent24]

Re: HannsG HH241 problems

Can someone point me in the right direction as to how to test these voltages?
* 5V for the main board, and
* voltage (14~17V) for the backlights inverter

I don't know where to put the leads of the multimeter. Thanks.

See the connector on the left of the board with the Red, Black, Blue, Yellow and Green wires? Seems to be marked CN8xx but I can't read the whole refdes. That is the connector which brings +5v to the mainboard and also carries control signals from the mainboard to control the inverter etc. Yours won't have the volume\mute signals connected though as your PSU\inverter board doesn't have the onboard audio amplifier.

There is a listing next to that connector showing the pinout for what each pin does. Pins 1 and 2 are 5v, pins 3, 4, and 10 are GND, etc etc.
Most likely there is a 1 and 10 marked on the board at either end of the connector showing which pin is which but I can't see them because the wire is in the way.

Going by the colours though, likely Red will be the +5v rail and Black will be ground.

So, get the monitor working and connect your black (negative) meter lead to ground on one of those black wires, and then connect the red (positive) meter lead to each other pin and write down what you measure for each one.

Then, wait until the monitor shuts down by itself, and measure everything again and write it down. Post the results here.

To find the Inverter power supply (it will run from a different rail than the +5v) we need to trace the PCB so you will need to take the board out of the case and show a good straight-on photo of both the top and bottom sides.

[budm]

Re: HannsG HH241 problems

Pin out.

[Davi.p]

Re: HannsG HH241 problems

To test the inveter supply you have to put the DMM in volt and red probe to the middle pin of the double diode on heatsink on top of the big transformer in Pic 3, the black probe on chassis. If you want to let your brain relaxed, you can start change the electrolitic caps, exept the bigger one, search online distributors (not ebay) for low esr types, search the forum for the better brands..

[Dougmeister]

Re: HannsG HH241 problems

So, get the monitor working and connect your black (negative) meter lead to ground on one of those black wires, and then connect the red (positive) meter lead to each other pin and write down what you measure for each one.

I connected the power (not the VGA input) and got the following results:

1: 5.05
2: 5.00
3: 0
4: 0
5: 0.12
6: 3.04
7: 0
8: 0
9: 3.28

Then, wait until the monitor shuts down by itself, and measure everything again and write it down. Post the results here.

Sorry, but I didn't know what you meant by this. I powered it off and then all the pins gave "0". I'm almost positive that's not what you wanted me to do.

I attached pics of the back of both boards.

[vinceroger69]

Re: HannsG HH241 problems

you need too wait for the monitor to power off by it self not you turning it off. when it powers off by its self, post the voltage readings again as we need to see what voltages are dissapering etc.

[Agent24]

Re: HannsG HH241 problems

Sorry, but I didn't know what you meant by this. I powered it off and then all the pins gave "0". I'm almost positive that's not what you wanted me to do.

The fault is that it shuts down by itself, right? Power it up,, leave it running, then wait until it shuts down. (The fault happens again)
At that point, measure all those voltages again.
Like vinceroger69 said, we need to compare the working and fault states to see what, if any of those voltages change.

[Dougmeister]

Re: HannsG HH241 problems

OKay. This is unexpected.

While I have it taken apart, it has been powered on and working for 15 minutes straight. It usually lasted less than a few minutes when it was put together...

I will see if it stays on much longer. Could it be something else other than the capacitors? I mean, 15 minutes would imply a different problem now, right?