Hanns-G HX192D power LED flashes

[PlainBill]

Re: Hanns-G HX192D power LED flashes

There's a silkscreen label under the connector that says (from top to bottom) +12V, GND, +5V, ADJUST. The top three pairs of pins are connected in parallel, but the Adjust pins are separate. One stays at .062V, the other stays at 4.94V. Pressing the power button does not change these. With the LCD panel disconnected, those both stay at zero.

Oh, and I have tested all of the caps on the digital board with the ESR meter. Only two were questionable (analog meter, mostly a go/no-go), and I replaced those. One of those still shows as questionable, but they're small-capacitance and I suspect there's some circuitry nearby that's affecting it.

I replaced most of the rest of the electrolytics on the digital board, but no change.

Is it right to think that the flashing power LED indicates that the microcontroller is at least partly alive?

Yes, that indicates the microcontroller is alive.

I wonder if we haven't wandered down a blind alley on this. The power supply appears to be working. The caps on the signal board appear to be good. The processor is working, and keypresses from the front panel are comunicated to the processor. The flashing light sometimes indicates corrupted flash memory (EEPROM). Googling found this link on resetting the monitor.

PlainBill

[jsog]

Re: Hanns-G HX192D power LED flashes

The 2 voltages you describe are interesting.
You mention .062v and 4.94v what does the silkscreen indicate these should be, is one dim and the other on? And I am also wondering why they change to 0v with the ribbon to the LCD disconnected.

The silkscreen only says "ADJUST". The traces can be seen on the back side of the IPS board, one leading back to Q1 and the other to R12. It's more interesting on the digital board.

The adjust lines are the two closest pins on the black connector. For orientation, the white piece at the bottom of the picture is the edge of CN5, the button cable connector.

The upper adjust line is tied to the top pin of the left transistor, Q2, also the 1K resistor above it, R13, pulling it to +5V. The lower adjust line goes to R19, the top pin of Q3 and C17, which is connected to ground.

[jsog]

Re: Hanns-G HX192D power LED flashes

Yes, that indicates the microcontroller is alive.

I wonder if we haven't wandered down a blind alley on this. The power supply appears to be working. The caps on the signal board appear to be good. The processor is working, and keypresses from the front panel are comunicated to the processor. The flashing light sometimes indicates corrupted flash memory (EEPROM). Googling found this link on resetting the monitor.

Actually had found that before, but it just says "Perform a factory reset in the monitor OSD (consult your manual for instructions)." There doesn't seem to be a reset procedure in the manual (http://america.hannsg.net/onweb.jsp?...bno=3333333375). There might be a magic button press sequence, but searches haven't found anything about it.

Note that the power LED goes green and starts flashing as soon as the AC cord is attached, without pressing the power button. Just now I've left it on for a few minutes (JP4 still disconnected), and the LED is still blinking green.

Don't think I've said it before: I do appreciate all the help. Thanks!

[jsog]

Re: Hanns-G HX192D power LED flashes

Numerous searches show that a lot of people with the HX192D and similar Hanns-G monitors have this problem. Eventually found this post on the I-INC CY199D and "Hanns.G" JW-199DPB, which are similar although maybe not identical. One poster claims replacing the 24LC16 EEPROM without programming the new one fixes it. If that's for real, I'd guess it's because it's used for keeping the user settings. They're cheap, 48 cents for the extended temperature range version from Digi-Key, 24LC16B-E/SN-ND. And there's only one of them on this board.

[PlainBill]

Re: Hanns-G HX192D power LED flashes

Numerous searches show that a lot of people with the HX192D and similar Hanns-G monitors have this problem. Eventually found this post on the I-INC CY199D and "Hanns.G" JW-199DPB, which are similar although maybe not identical. One poster claims replacing the 24LC16 EEPROM without programming the new one fixes it. If that's for real, I'd guess it's because it's used for keeping the user settings. They're cheap, 48 cents for the extended temperature range version from Digi-Key, 24LC16B-E/SN-ND. And there's only one of them on this board.

That would confirm the 'corrupted EEPROM' theory. Something else you could try is 'panning' for a reset combination. This is done by holding down all possible combinations of buttons while applying power to the monitor. The best way to do this would be to position the monitor so you can hold the buttons down with the fingers of one hand. Plug the monitor into a power strip. With one hand hold one or more buttons down, with the other turn on the power strip.

While it seems like a daunting task, there are only 31 possible combinations of buttons (15 if you ignore the Power button). It should take less than half an hour to try all combinations.

PlainBill

[jsog]

Re: Hanns-G HX192D power LED flashes

Just tried all 31 combinations of the buttons with no change.

My hope is that the EEPROM failed due to heat. The data sheet says it's good for a million erase/write cycles, so it probably didn't just wear out. The full text on it is: 24LC16B, SN 0605, 24B. The chip next to it is labeled PS25LV010, -33E N18S2, 0545BAN. Searches show that's probably the same as a PM25LV010, a 128K x 8 serial flash. Guessing that's where the microcontroller program is stored.

There are also two 24LC02B 2K EEPROMs, one near each video connector. Maybe those are for EDID info.

Jumper J2 ties either the 1.8V or 3.3V supply through C25 (10 uf, 25V) to ground. 3.3V the way it is set. Can't see why that needs a jumper.

[PlainBill]

Re: Hanns-G HX192D power LED flashes

Just tried all 31 combinations of the buttons with no change.

My hope is that the EEPROM failed due to heat. The data sheet says it's good for a million erase/write cycles, so it probably didn't just wear out. The full text on it is: 24LC16B, SN 0605, 24B. The chip next to it is labeled PS25LV010, -33E N18S2, 0545BAN. Searches show that's probably the same as a PM25LV010, a 128K x 8 serial flash. Guessing that's where the microcontroller program is stored.

There are also two 24LC02B 2K EEPROMs, one near each video connector. Maybe those are for EDID info.

Jumper J2 ties either the 1.8V or 3.3V supply through C25 (10 uf, 25V) to ground. 3.3V the way it is set. Can't see why that needs a jumper.

Which ICs are powered through J2? If it's only the 24LC16B, it would be interesting to see the effect of disabling power to it. Other monitors will work if the corrupted EEPROM is removed, but it is not possible to save user settings. Disabling power might have the same effect.

PlainBill

[jsog]

Re: Hanns-G HX192D power LED flashes

I can't find any ICs powered by J2. The center pin links to Q4, the right pin in the picture. From there, the output appears to go through the two S1As transistors (Q5 and Q6) and then eventually the output of Q6 goes through a 472 resistor and back to a pin on the left side of the processor.


I'll replace C25 and test again just in case.

After that, is there any reason not to remove the 24LC16 and test without it?

[PlainBill]

Re: Hanns-G HX192D power LED flashes

I can't find any ICs powered by J2. The center pin links to Q4, the right pin in the picture. From there, the output appears to go through the two S1As transistors (Q5 and Q6) and then eventually the output of Q6 goes through a 472 resistor and back to a pin on the left side of the processor.


I'll replace C25 and test again just in case.

After that, is there any reason not to remove the 24LC16 and test without it?

Nope.

PlainBill

[jsog]

Re: Hanns-G HX192D power LED flashes

Well, that made a difference. Instead of a fast flashing power LED as soon as AC is connected, it's flashing slower, about 1 Hz. The inverter whine goes on and off in sync with the LED as before. I'll report back after replacing the 24LC16B. Thanks again!

[jsog]

Re: Hanns-G HX192D power LED flashes

With a new, blank 24LC16, there's new behavior. When power is applied, the power LED goes amber then quickly changes to solid green. Nothing else happens, the inverter whines solidly but the backlights don't go on. All 31 combinations of buttons held on powerup don't make a difference. Left alone for ten minutes or so, the LED stays green.

Make that "presumably blank 24LC16" above. They might come from the factory with random data, all zeros, or all ones.

Almost time to throw it on the parts pile. The IPS board seems good, the panel looks okay. It's tempting to switch J2 and see what happens.