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Returning briefly to the HannsG monitor, today I did a test by connecting it to the New PC IN (Phenom), everything went as I thought, it is back to work, but at some point the PC shuts down or restarts, however the problem must be in the PC , since the monitor remains with the orange LED, after a few attempts I can restart the PC, it displays a BIOS screen, with a message that I do not know exactly what it means, it says DQS training failed on previous boot. .. etc...

At this point, after several shutdowns and re-starts, the monitor turns off and nothing can be seen, in the doubt that it is a video signal problem, I connect another monitor and this shows that the video signal is there.

Another attempt I connect the monitor without the VGA cable, and I try to turn it on, unfortunately the LED remains off and therefore, my prediction that the repair could last several years, turned out to be too optimistic, I later decide to disassemble it to check the control board power supply, there is nothing evident that it is broken, I check the two fuses but they are ok, tomorrow I will check the other capacitors, in total there are three plus one large, I hope to find one KO, otherwise it will not be easy to find which component is faulty, I would exclude that the fault is in the minicard with the VGA port, there are also small capacitors there, but since the PWR LED remains off, it makes me think that it is a problem with the power board.

Fortunately, having the other monitor, I have not been without in a PC, I will see anyway if I can recover it (again), because it is quite comfortable, being quite compact and light, it is easily moved from one location to another.

I'm all for saving stuff from the landfill or even from recyclers, but is there anything special enough about this specific monitor to justify all the effort you are putting into it ? Aren't there other monitors more worthy of this ?

The thrill of the challenge is obviously reason enough, so I am not judging.. I partially recapped (just 2 caps, actually, 😉 ) the internal PSU of an LG L246WP (VA variant, with a black crush that I was never fully able to compensate for) to bring it back to life after 10 years of ownership and some would have argued (and did 😉 ) that it wasn't worth the effort of even disassembling it, but it was arguably fun and a learning experience for me.

In this case, is the monitor special to you for a reason or is it mostly a question of wanting to just get it working because you can (as mentioned before, a great reason in and of itself)?

darry wrote on 2022-11-02, 22:10:

I'm all for saving stuff from the landfill or even from recyclers, but is there anything special enough about this specific monitor to justify all the effort you are putting into it ? Aren't there other monitors more worthy of this ?

The thrill of the challenge is obviously reason enough, so I am not judging.. I partially recapped (just 2 caps, actually, 😉 ) the internal PSU of an LG L246WP (VA variant, with a black crush that I was never fully able to compensate for) to bring it back to life after 10 years of ownership and some would have argued (and did 😉 ) that it wasn't worth the effort of even disassembling it, but it was arguably fun and a learning experience for me.

In this case, is the monitor special to you for a reason or is it mostly a question of wanting to just get it working because you can (as mentioned before, a great reason in and of itself)?

Sorry I'm late for my reply.
So, first of all I'm not a professional repairer, and I can devote all the free time I need to it, the monitor is mine (so I don't fix it for someone), if I wanted I could find other monitors that work, and they don't cost much, but in the past I fixed a lot of power supplies, so setting up this monitor was pretty straightforward, and in fact it was as long as it worked.
Having broken down again, it makes repairing difficult, because now the failure is not visible, while before it is (see capacitors).
Now, I still don't understand what the problem is, i.e. if there is a power failure somewhere, I have ideas but I didn't have time to check, it could also be a stupid broken power cable, but I usually do some checks target suspicious components, and if you find something faulty, it easily gets back to work.
I have other monitors that I could repair, in particular I have an ACER with a backlight problem, it turns off after a few seconds, I think it can be fixed by deactivating one of the four lamps, but I don't know exactly how to go about it without that broken one.

PC@LIVE wrote on 2022-11-07, 21:50:

Sorry I'm late for my reply. So, first of all I'm not a professional repairer, and I can devote all the free time I need to it, […]
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darry wrote on 2022-11-02, 22:10:

I'm all for saving stuff from the landfill or even from recyclers, but is there anything special enough about this specific monitor to justify all the effort you are putting into it ? Aren't there other monitors more worthy of this ?

The thrill of the challenge is obviously reason enough, so I am not judging.. I partially recapped (just 2 caps, actually, 😉 ) the internal PSU of an LG L246WP (VA variant, with a black crush that I was never fully able to compensate for) to bring it back to life after 10 years of ownership and some would have argued (and did 😉 ) that it wasn't worth the effort of even disassembling it, but it was arguably fun and a learning experience for me.

In this case, is the monitor special to you for a reason or is it mostly a question of wanting to just get it working because you can (as mentioned before, a great reason in and of itself)?

Sorry I'm late for my reply.
So, first of all I'm not a professional repairer, and I can devote all the free time I need to it, the monitor is mine (so I don't fix it for someone), if I wanted I could find other monitors that work, and they don't cost much, but in the past I fixed a lot of power supplies, so setting up this monitor was pretty straightforward, and in fact it was as long as it worked.
Having broken down again, it makes repairing difficult, because now the failure is not visible, while before it is (see capacitors).
Now, I still don't understand what the problem is, i.e. if there is a power failure somewhere, I have ideas but I didn't have time to check, it could also be a stupid broken power cable, but I usually do some checks target suspicious components, and if you find something faulty, it easily gets back to work.
I have other monitors that I could repair, in particular I have an ACER with a backlight problem, it turns off after a few seconds, I think it can be fixed by deactivating one of the four lamps, but I don't know exactly how to go about it without that broken one.

Ack, TY for explaining.

Did you end up removing and checking the non-swollen caps you mentioned or is that still on the TODO list ?

Monitors with bad PSUs or backlight issues are definitely more worthy of repair than the item in the story below.:

Around 2005-ish I had a bog standard 40$ (AFAICR) drip coffee maker (got it as a gift) whose heating element stopped working. I tore it down (had to cut the plastic around a one-way screw) to find that the thermal cut-off had failed open (better than opposite failure mode). I tried sourcing one locally (couldn't get anything close to the temp value) or online (would have had to buy a multi-pack) so I eventually took a chance on a thrift store 1$ coffee maker whose carafe was missing but contained a working part similar similar enough (10 degrees lower than what I needed) that I could proceed with the repair (after macgyvering a retention system as new part was same size and shape but had a different mounting design, AFAICR).

The coffee maker then worked fine for a few months until... the handle, which was only glued to the carafe came loose in my hands while I was washing the carafe!!! What a stupidly dangerous design, IMHO (the new one I got and still use has steel rings in addition to glue)!! That was the last straw and I junked the whole thing.

TLDR : Some broken stuff just really wants to fight its way into recycling/scrap and arguably deserves it. 😉

So, it's been a long time since I disassembled this monitor, after the repair it broke, so I tried to replace other capacitors, thinking that maybe they could be the problem.
In reality this is not the case, the power supply seems to work, but there is no STBY voltage, it should be around 5V (I imagine), it could be 12V or more, since I don't have much experience in repairing monitors, I did some research on the subject, checks need to be carried out, the problems with the capacitors have been solved by changing them with new ones, of course if bad luck wants it, one of the replaced ones could have broken, perhaps it is unlikely but not impossible, perhaps a check could dispel any doubt.

I return briefly to the topic, the repair and failure of the monitor, I searched for info, and I found how the boot circuit should work.
There are two transistors connected together, and in turn they should be connected to an IC, long story short, the two transistors command the monitor to start, sending a signal to the IC, in conclusion, I should locate the components on the monitor's power board , and hope that there is some visible damage (under the microscope perhaps), if there is nothing visible, you need to do some measurements.
Theoretically it should be a fairly simple circuit, but it might not have any problem, since that is a start circuit, and this doesn't seem to be the problem, since the STBY current is missing, so perhaps it would be better to start from the STBY circuit, assuming I can identify it, I'll post some photos, maybe I might miss something.

As regards this monitor, I suppose there was a fault in the secondary, with possible involvement of the primary, strangely however the intact fuse makes me suppose that the primary may be ok, there is probably an interruption in a component in the secondary, maybe a diode?
If confirmed by instrumental checks, it will be enough to change a component to have the monitor working.
A fairly simple hypothesis, which must be verified instrumentally, the suspect is the large diode (or mosfet?) in the secondary, near the transformer.
At this point I would rule out a failure of the smaller board (with VGA port), I hope I'm right, and as soon as possible I'll do some tests and measurements, with the plug inserted and the power button ON.

From the time when I repaired monitors many years ago (when I was in school), I would guess that 5V and 12V are always on and ADJ is a combined backlight enable/brightness control. I don't know what the logic board is doing with 12V.

Missing standby power with no blown fuse could be the two small electrolytic caps on the power supply or the two diodes on the heatsink that you're suspecting. You could also try powering it up with the logic board removed in case there's a short on that board. Adding some pictures of the bottom of each board (with more light) would help with the remote troubleshooting.

lti wrote on 2024-06-30, 03:12:

From the time when I repaired monitors many years ago (when I was in school), I would guess that 5V and 12V are always on and ADJ is a combined backlight enable/brightness control. I don't know what the logic board is doing with 12V.

Missing standby power with no blown fuse could be the two small electrolytic caps on the power supply or the two diodes on the heatsink that you're suspecting. You could also try powering it up with the logic board removed in case there's a short on that board. Adding some pictures of the bottom of each board (with more light) would help with the remote troubleshooting.

Thank you so much my friend.
In fact I was actually thinking about that pair of diodes, I think that after removal and checking, if I find something abnormal (faulty?), by changing that or those, it can go back to normal.
I do repairs as a hobby, it's not a job, I repair my things, I have other working monitors, but I'm sorry to throw it away, among other things I get by with PC power supplies, this is more or less the same thing, I'm talking about the power board.
I will try as soon as possible to do as you suggest, hoping that the problem will be resolved, because it would be useful for me to make room on the bench.

Here are some photos, they are taken in a bit of a hurry, I can definitely do better, for the moment I think it can be a starting point.
I noticed on the back of the small card (with VGA port), that in some pins of a connector there are some writings, referring to the single pin, which can help to understand if the voltage is missing.
On the back of the large board (power supply), there are various more or less tiny SMDs.
Today I don't think I'll be able to do any work, but I might in the next few days.
The first check will be done by removing the two diodes (connected to the heat sink), having already replaced the capacitors in that area, it seems strange to me that there is a problem with those capacitors.

lti wrote on 2024-06-30, 03:12:

From the time when I repaired monitors many years ago (when I was in school), I would guess that 5V and 12V are always on and ADJ is a combined backlight enable/brightness control. I don't know what the logic board is doing with 12V.

Missing standby power with no blown fuse could be the two small electrolytic caps on the power supply or the two diodes on the heatsink that you're suspecting. You could also try powering it up with the logic board removed in case there's a short on that board.

I second what lti said above.

Issue could be with the power supply or the logic board itself. So isolate the two. That is, run the PSU board by itself. Indeed you should get 5V and something close to a 12V rail (could be 12V, could be 13V, could be 15V.... it's not always a very-well defined rail as it's used by the inverter circuit and isn't monitored too closely). Both of these rails are always-on, as lti guessed correctly. So as soon as the PSU is plugged in the wall, you should see those output voltages with or without the logic board connected.
Now, if you don't see these voltages even with the logic board disconnected, then the issues is more likely to be either a bad rectifier / diode on the output on one of the rails, a bad startup cap (doesn't look like you replaced it, it's C123 on the board), or the inverter driver transistors are shorted, thus pulling the entire output low. For the last one (shorted inverter transistors), you can usually isolate/disconnect the inverter circuit if you follow the 12V rail. Often times, there's a jumper that connects it to the 12V rail. Remove the jumper if you suspect shorted transistors and the PSU should start right up after this.

momaka wrote on 2024-07-09, 23:42:

I second what lti said above. […]
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lti wrote on 2024-06-30, 03:12:

From the time when I repaired monitors many years ago (when I was in school), I would guess that 5V and 12V are always on and ADJ is a combined backlight enable/brightness control. I don't know what the logic board is doing with 12V.

Missing standby power with no blown fuse could be the two small electrolytic caps on the power supply or the two diodes on the heatsink that you're suspecting. You could also try powering it up with the logic board removed in case there's a short on that board.

I second what lti said above.

Issue could be with the power supply or the logic board itself. So isolate the two. That is, run the PSU board by itself. Indeed you should get 5V and something close to a 12V rail (could be 12V, could be 13V, could be 15V.... it's not always a very-well defined rail as it's used by the inverter circuit and isn't monitored too closely). Both of these rails are always-on, as lti guessed correctly. So as soon as the PSU is plugged in the wall, you should see those output voltages with or without the logic board connected.
Now, if you don't see these voltages even with the logic board disconnected, then the issues is more likely to be either a bad rectifier / diode on the output on one of the rails, a bad startup cap (doesn't look like you replaced it, it's C123 on the board), or the inverter driver transistors are shorted, thus pulling the entire output low. For the last one (shorted inverter transistors), you can usually isolate/disconnect the inverter circuit if you follow the 12V rail. Often times, there's a jumper that connects it to the 12V rail. Remove the jumper if you suspect shorted transistors and the PSU should start right up after this.

Hi, thank you very much for the advice, unfortunately I only noticed your answer now, and in truth in this period I am carrying out other activities, which do not allow me to take care of the hw under repair.
In the past I also wrote on Badcaps, and I remember you, unfortunately I don't have much experience in repairing monitors, while in the past I had enough with power supplies, and more recently with motherboards.
My equipment is a bit limited, and I don't have an oscilloscope, but with the testers I have I think I might be able to find the (or the) faulty components.
Maybe in the next few days, taking advantage of the holidays, I could try to re-examine the monitor and see if I can do some tests.
I repair it only because, it is my first LCD, and it is very useful for MB tests, as it is quite compact and light, I can easily move it somewhere else.