Re: Hanns g 28" Monitor Power Supply Question
When I selected the caps from the parts selector, Digikey gives the Panasonic ECG as a global selector. After looking at the caps selection post, I discovered that some of the caps I purchased were FM and some FC.
And now I understand why the global listing for Digikey for Panasonic is ECG.
These electrolytics are a new thing for me. I was an EE in the defense industry for a decade. Electrolytics are expressly prohibited by all customers so looking for them right off the bat (in addition to having no...
Steven_C
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Last Activity: 04-11-2013, 03:03 PM
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Re: Hanns g 28" Monitor Power Supply Question
That answers my question regarding CCFL's and which electrolytics you folks recommend.
BTW, would forced air on the electrolytics increase their life? There appear to be electrolytics which quickly fail on this monitor. I purchased it as a refurb (and after opening it, it clearly had been repaired my the manufacturer previously) and it lasted 7 months for me. Bill indicated in another post that reducing the brightness to 30% increased their life so I've done this.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
So the "CCFL's" (high voltage transformer) can be substituted from smaller monitors? There are 7 of these transformer units on the board but it looks like there are 2 per install.
If using 2 in series from the 19" or 22" in series, I assume the step up for the two is equivalent to one of these ccfl's?Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
It was a fault condition Bill. I had bent one of the 7 power inverter pins going to the lcd and hadn't caught it until this second time after reading your post and removing and reinstalling. The connector to the lcd wouldn't fully seat so I rebent the pin. All 7 CCFL's (a high voltage transformer for the lcd display I assume?) are connected. The fault condition is now gone.
It looks like the monitor is now fully functional again.
BTW, are the panasonic ecg caps one of the recommended caps? They are...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
Bill/Momanka,
I got the P/S board reworked and have very clean 5V, 12V, and 24V outputs at CN1 and CN3 under load (i.e. monitor turned on). The monitor turns on, I get a picture for 1 second, then the monitor turns off yet the blue led stays lit.
Where would you folks look to next?Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
I will do that momanka. You and Bill have been very helpful and I am very grateful. I'm waiting for rework parts as they haven't come in yet.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
momanka/Bill,
I just figured out my problem. I can't believe it's taken me this long. momanka got me to thinking that there might be another way to turn Q202 on because the polarities of the diodes on that timer chain made it impossible. There is. U202 is a DIP (lm393) whereby pin 1 is an output on that timer chain. It sources the base of Q202 low via R210.
When I probed the op amp output to see if it was pulling the base low, it was behaving as if the output was floating with Vs so I figured the ground...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
momanka,
The collector of Q202 does in fact also continue through jumper resistor JR9 down to R133 over to R134 then to pin 6 of U102. Those are good size resistors (i.e. 1k+) which makes me think that chain doesn't supply Vs to U102. However, Vs is tied to the emitter of Q202, while the collector is tied to Vs of U102 which makes me think this transistor turns on power to U102. Unless I'm mistaken, until I get power to U102, I'm sort of dead in the water with respect to getting voltage to the primary of the 12V/24V...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
I tried toggline PSON and I got the same result. The output of that timer seems dead or is not outputting anything when Vs on the timer goes to 14V DC.
One part of this circuit I haven't figured out is that the two diodes between the timer output and base seem to be in reverse to the base-emitter polarity. I get a diode drop between pin's 3 and 1 (i.e. emitter-base) of the transistor which makes me think it's a pnp. There are no other diode drops across any combination of pins on the transistor. Under this configuration,...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
Bill, I think I might have figured out the problem but I'm not sure. U202 mosfet based 555 timer.
It's output (i.e. pin 3 of U202) connects through two resistors and two diodes to pin 1 of Q202 (i.e. the base). When Vs to U202 is 14V, since no current is drawn at the transistor base, 15V DC is seen right up until the timer output. It is 15V except at the output of U202 which is 0V. I ohmed the output of U202 with respect to ground and it comes out to 300 or so ohms but slowly creeps up.
...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
The collector is connected to Vs of U102.
The base and emitter are at the same voltage (i.e. ~ 13V DC). So Q202 is not being turned on. Normally, Vcc is tied directly to Vs of an ic. Perhaps my problem lies elsewhere ... I'm just not finding another direct connection to Vs of U102.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
With respect to Q202, I made a mistake. The the center pin (i.e. pin 2) and tab (other side of the transistor) appear as a short. Pin's 1 and 3 are independent electrically. Pin 1 is connected to pins 4 and 8 of U202, while pin 3 connects to a surface mount transistor. I'm guessing that pin 3 is the on/off pin?Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
After looking at that datasheet for the controller, it looks like the zener on pin 12 internal to the ic could be shorted to ground. The only way I'd know if that were the case would be to remove U102 and probe pin 12 again.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
It looks like 3 of the 4 pins from Q202 source Vs on U102. One pin on Q202 is sourced from pins 4 and pins 8 of U202. That pin is reads ~ 14.5V DC. So is Q202 configured like a diode even though it's a transistor? If so, then I'm guessing Q202 is open.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
I used some rubbing alcohol to get the conformal coating off of the ic. I can then read the P/N with a flashlight at the "right angle". It's P/N for U102 is L6598D.
[url]https://cdn.badcaps-static.com/pdfs/5a4649ef5646c3665ddc5d1b218cda6e.pdf[/url]
I have no power to pin 12 with respect to pin 10. What sources the required 10V to this controller?Re: Hanns g 28" Monitor Power Supply...ic. I can thenLeave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
Bill, I don't have power to U102. There is no DC voltage at any of the 16 pins.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
Bill, do you have a p/n for U102? It's a 16 pin surface mount ic which I don't see on your schematic. A p/n cannot be read off the surface of the ic so I'm uncertain what I'm looking in probing the various pins.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
CP812 in your schematic corresponds to the large cap on this board underneath the heatsink. When PSON is enabled, the voltage is in fact ~ 380V DC. When PSON is off, it drops very slowly down to ~ 165 V DC. It jumps to 380V very quickly, but takes a couple of minutes to drop down to 165V DC.
Any suggestions up to this point? It looks like the PFC correction circuit is operating properly. I'm following your schematic as my board appears to be very similar.Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
Measurements:
(1) 12V/24V transformer input (one with respect to the other) is less than a volt with a very poor sinusoid.
(2) The rectifier (D10XB60) input is +/-160V peak to peak.
(3) The rectifier output (i.e. pin 1 referenced to pin 4) is 160V DC.
(4) D1 and Q101 have no shorts.
This rectified input leads to a yellow transformer which sits underneath the heatsink. (see 1st pic) Assuming this rectified input is the dotted input to the transformer, the...Leave a comment:
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Re: Hanns g 28" Monitor Power Supply Question
I think I understand Bill. That datasheet I believe helped me grasp this concept. I could be measuring what I think is a 150V sinusoid peak to peak when in fact a fluctuating reference gives me a meaningless reading. Moreover, a chassis ground reference is only useful with respect to a secondary measurement because the ground is the reference for that side whereas it is not on the primary.
So if I understand correctly, the isolation transformer kills any DC which would affect a scope reading via the common neutrals...Leave a comment:
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