Hanns-G HG281D, LCD Monitor no power

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

U601 looks like DM0265R

http://pdf1.alldatasheet.com/datashe...SDM0265RL.html

Pin 1 is GND, pin 2 is VCC. See if pin 2, VCC, has stable DC voltage or not. It should be 12V DC according to datasheet, page 5 and 9.

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

U601 looks like DM0265R

http://pdf1.alldatasheet.com/datashe...SDM0265RL.html

Pin 1 is GND, pin 2 is VCC. See if pin 2, VCC, has stable DC voltage or not. It should be 12V DC according to datasheet, page 5 and 9.

Confirming DM0265R, scraped some of the paint off pic attached, I will do those checks

Thank you very much budm/retiredcaps
Dan

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

U601 looks like DM0265R

http://pdf1.alldatasheet.com/datashe...SDM0265RL.html

Pin 1 is GND, pin 2 is VCC. See if pin 2, VCC, has stable DC voltage or not. It should be 12V DC according to datasheet, page 5 and 9.

That ulr points to a FS DMO365R data sheet, page says 265 but the printed data sheet lists 365, looks quite similar to the attached DMO264R.
Dan

[Recycler]

Re: Hanns-G HG281D, LCD Monitor no power

OK I tested the 5v supply to the main board. This is the 5vsb (Stand By 5v) without connection to the main board the voltage is rock staedy at 5 volts, connect the main board the and the 5vsb fluctuates 3.6 to 5.1. Dan

Don't bother with the smps IC. If you have 5v standby, most probably the smps is OK because if not the PSU wouldn't come up at all.

Also note that modern smps have protection build-in. If the current rises above certain level the smps shuts down. The fluctuation you are seeing might be just that.

If a the standby current is rated at 1.5A, it doesn't mean that it has to pull 1.5A. I can't imagine this monitor draws that much on standby. It would typically be much lower than that.

For now, just focus on the caps because I think you are digging in to much.
Test the 5V SB with some load (a lamp is perfect) and if it lights up OK then your logic board has a problem.

Cheers.

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

If the 5V SB is fluctuating with only 40ma current draw, then you need to get this section working first. I use 6v lamp as a load for 5VSB testing, you can get 6v 250ma from Radio Shack, that way you will not have plug/unplug it from the main board, I also use 12V 10~20Watts car lamp for testing the 12V section, and 2 12v in series for the 24v section, this way I can test the power supply by itself.

I already suggest using lamp for the 5VSB and also suggested the caps in the primary side. Just cannot get through.
Retiredcaps aslo suggesting the same. He need to get the standby power supply to be stable first!

[kschultz]

Re: Hanns-G HG281D, LCD Monitor no power

I found your site while trying to get info on this monitor that would not power up. I read through these posts and changed all capacitors on the logic card and the ones that we had in stock from the power supply card. The monitor has been powered on for about 4 hours now and appears to be working fine.
Thank you for all of your help.

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

I tested voltage between ground pin1, and Vcc pin 2, on SMPS DM0265R , it reads a jittery 10.56v to 11.32v as recorded on Fluke 85. I tested all caps suggested on page 1 and 2 of this thread as suggested by budm in post 197 ,all tested OK. Had to replace the bridge, 120vac fuse and about 2 inches of trace on the PS, a naughty ground clip from the scope poped off, went where it should'nt, sounded like a little red, firecraker. I measured the jittery 10.56v to 11.32v on the SMPS gnd/Vcc before the accident, all appears to be as it was now. Is the jittery 10.56v to 11.32v normal?, not sure where else to look.

All suggestions appreciated

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

I tested all caps suggested on page 1 and 2 of this thread as suggested by budm in post 197 ,all tested OK.

I realize your profile says Professional Tech, but I have to ask what did you use to test the cap with? What readings did it give for the caps? We got all sorts of people and how they arrive to the conclusion that caps are good varies.

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

I tested using Sinometer 6013 Capacitance meter pic attached, while observing polarity I measured in circuit cap values and if I could not read the minimum value I would remove, test and reinstall. I normally do not get into board level diagnosis (as pervious post,-blown fuse/bridge might attest - embarrassing). After thinking about this I am puzzled that the caps totaling about 1300 uf measured at the PS 5vsb terminal does not hold the 5vsb steady , when I measured only 40ma current draw, wondering if there is a ringing/resonance going on between the PS and main board 5vsb connection. The AC input going into the single diode that supplies the 5vsb is like I show it on a previous post showing the scope trace, the AC is still pulsing hi frequency 4khz to 9khz, this pulsing in the same rate as the 5vsb fluctuations with main board connected or not connected. I would give my last beer to get a copy of this Power Supply schematic as I think the oscillation circuit that controls the AC supplying the 5vsb is what is gone defective.

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

I tested using Sinometer 6013 Capacitance meter pic attached, while observing polarity I measured in circuit cap values and if I could not read the minimum value I would remove, test and reinstall.

1) The 6013 only measures capacitance and not ESR (equivalent series resistance). To measure ESR, you need an ESR meter.

2) Measuring capacitors in circuit is not 100% reliable. When capacitors are connected in parallel, the total capacitance is the sum of the individual capacitors' capacitances.

3) Tom66 has reported and measured BAD caps that were HIGHER than the stated capacitance. For example, a bad 1000uF cap would measure 1500uF. He measured it with the $100 BK Precision shootout winner.

4) Taking #2 and #3 into consideration, if the caps are in parallel it is possible for the following scenario. Assume 2 caps that are rated for 47uF each. One cap reads 20uF and the other reads 74uF. Testing in circuit yields 94uF leading the user to think both caps are good.

5) I have mentioned it several times that for this particular monitor, it runs temperature hot which leads to dry caps on both the power and main board.

6) With the history of this monitor, my #1 suspect for the fluctuating DC votlage are still the caps (unless verified out of circuit with an ESR meter). If changing out the caps doesn't solve the problem, then I would suspect the SMPS IC.

7) 95% of the DC voltage fluctuating problems here that I have observed in almost 2 years have been due to the startup cap or the SMPS IC controller.

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

The Standby 5vsb is now working and the the blue power on and amber standby led on monitor front indictes power and recognize when video is connected - toggles front blue to amber as it should. Attached is location of slightly under value cap C114 -labled 2.2 uf measured 1.7, see attached pic showing location. The 5vsb is a rock steady 5.1v

The problem now is there is no image showing , ther is no 5v or 12 v or 24v on the labled output terminals of the PS.

I suspect this problem originates from the blown trace/fuse when the scope ground clip went where it should not in per previous post.

Are there any othe fuses other than the 120vac fuse on this PS?

Any suggestions would be greatly approciated

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

Attached location of C114 , for some reason teaxt not does not showing on jpg

[Jasgriff]

Re: Hanns-G HG281D, LCD Monitor no power

Did you take it out to test?

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

I tested the PS connected to the rest of the monitor components and removed but always connected to the main board, the main board needed to turn on the 5/12/24v supplies. I have attached pics of the PS with and without transformer, I removed the xformer to inspect its underside as I thought I saw/heard a click/pop from its underside.

[Jasgriff]

Re: Hanns-G HG281D, LCD Monitor no power

What's the patching on the board in the middle and the top left?

Were you not getting anything on any of the connector pins?

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

there is no 5v or 12 v or 24v on the labled output terminals of the PS.

The main board is responsible for sending the PS_ON command to the power board to turn on the secondary voltages.

On the connector from the power board to the main board, see if there is a pin marked PS_ON. It should be 3V DC or higher. If not, the problem lies on the main board.

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

The pin maked PS-ON on the connector that goes to the main board (black wire end of header) toggles between 0v with amber led(input not detected) and 3.169v with blue led(input detected).

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

The main board is responsible for sending the PS_ON command to the power board to turn on the secondary voltages.

On the connector from the power board to the main board, see if there is a pin marked PS_ON. It should be 3V DC or higher. If not, the problem lies on the main board.

Is it likely to cause damage to jumper the PS-ON to the 5vsb?

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

Is it likely to cause damage to jumper the PS-ON to the 5vsb?

Use a resistor as suggested below

https://www.badcaps.net/forum/showpo...9&postcount=45

[DIODE]

Re: Hanns-G HG281D, LCD Monitor no power

What's the patching on the board in the middle and the top left?

Were you not getting anything on any of the connector pins?

Jasgriff See post 207, the top left is temp 3A fuse wire.