Re: HP 1955 Monitor Repair Guide
YES! We found the problem. I desoldered the gray box caps then resoldered them. I mounted the bord on the back of the LCD, started it and it worked!
Im gonna give it some time off and stuff till I feel sure that its really fixed.
I just want to say Thank You to all of you for helping me out debugging the board. I love this place!
krantz
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Last Activity: 04-06-2022, 07:29 AM
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Last edited by krantz; 11-07-2011, 10:14 PM. -
Re: HP 1955 Monitor Repair Guide
You mean what uF and V-capacaty?
I never desoldered the gray box type caps but the 5707's. Only the one in the picture to know what it was.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
I tried it. At first I used just one connector from the CCFL and it worked. Tried two, worked. Tried three, worked. Tried four, it started flashing on and off but the power switch LED did not flash (restart). Tried it again and now the test-CCFL's stay on and the power switch isnt restarting.
Tried it again after having the power cord unplugged - the CCFL's and power-switch LED is restarting again. Caps anyway?...Leave a comment:
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Re: HP 1955 Monitor Repair Guide
No, I dont.
I have a lcd monitor that has a CCFL in it but can I get it out to test the board with it?Leave a comment:
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Re: HP 1955 Monitor Repair Guide
All the caps i replaced to are Rubycon.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
The caps (two battery shaped) at the ic?
Or the two blue ones at the power-connector?
Updated: Electrolytic capacitors, yeah. Like I said. I changed them all.
I guess I need to wait for my new multimeter (Fluke 179) so that I can check the capacitors with that. Maybe they're defective?...Last edited by krantz; 11-07-2011, 05:55 PM.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
You mean the two grayish rectangular components at the power connector and the two at the transistors?
Refer to attachment pictures....Leave a comment:
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Re: HP 1955 Monitor Repair Guide
That is correct. But when I removed the fuse I didnt get a picture or the backlight didnt power on. (?)...Leave a comment:
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Re: HP 1955 Monitor Repair Guide
Ah, sorry.
I get a picture from the computer with working backlights for about a second, then the screen restarts in an continous loop. Also the power-on-board on the front of the LCD restarts with the green LED lighting on and off at the restarts.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
Restatement: I have a 1955 that I am trying to get working. I have changed all the caps except for the 150uF 450v. I cant see any blown FET's or anything else that might be shorted. What could it be?
Plus I found out that there are two more caps on the power board where the C5707's are and two more at the power-connector. The grayish ones.
I have desoldered the inverter fuse 5A 125V, measured it and it has very low resistance (0.4 ohms).
I have measured the 4431 FET's, the signaling transistors (no shorts,...Leave a comment:
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Re: HP 1955 Monitor Repair Guide
The logic board is the board with the the connectors on it? (DVI, VGA, USB etc.?)Leave a comment:
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Re: HP 1955 Monitor Repair Guide
Oh, haha. Sorry.
Though Im guessing this is a dead end with this board?Leave a comment:
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Re: HP 1955 Monitor Repair Guide
Ok. In that case I only get 1 on the left hand side of the multimeter display.
I have allready taken pictures of the board on top and underneath and even given links to the full resolution pictures on my webserver.
Thanks for the info about the multimeter btw!...
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Re: HP 1955 Monitor Repair Guide
I get nothing on the transistors at that measuring, jetadm123Leave a comment:
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Re: HP 1955 Monitor Repair Guide
I start the measuring from the top transformer...
188.6 ohms
184.3 ohms
187.1 ohms
188.5 ohms...Leave a comment:
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Re: HP 1955 Monitor Repair Guide
I measured the signaling transistors that also is in the repair guide and I got some strange readings.
The left top gave me:
B-C: 0.724v
B-E: 0.730v
C-E: 0.762v
E-C: 0.780v
The left underneath gave me:
B-C: 0v
B-E: 0v
C-E: 1.660v
E-C: Open
The bottom left gave me:
B-C: Open
B-E: 0.733v
C-E: 0.977v
E-C: Open
The bottom right gave me:
B-C: 0.725v
B-E: 0.731v
C-E: 0.763v
E-C: 0.776v
Maybe some...Last edited by krantz; 11-06-2011, 09:20 PM.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
I measured the SMD 4-pin 4431 Backlight ON/OFF FET's. From drain to source I got 0.535v-0.540v, and from source to drain i got overload.
I measured the inverter fuse and it gave the resault of 0.05 ohms.
But what is the "secondaries of the inverter transformers" and where do I find it on the board?...Last edited by krantz; 11-06-2011, 06:48 PM.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
Im guessing I need to solder the SMD's out to measure them? In that case I need to wait for my hot-air-station that I ordered yesterday....Last edited by krantz; 11-02-2011, 12:44 AM.Leave a comment:
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Re: HP 1955 Monitor Repair Guide
I soldered out the C5707's and here are the results of those with my DMM...
All gave these readouts...
B-C: 0.639v
B-E: 0.639v
C-E: Open
E-C: OpenLeave a comment:
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Re: HP 1955 Monitor Repair Guide
Lets try that again shall we?
Here are some new full-surface pictures.
If you want there are fullsize pictures here... [url]http://gkdv.se/bilder/Elektronik%20&%20Komponenter/Bildsk%c3%a4rmar/HP%201955/111030/Fullsize/[/url]
Update: I removed the fuse and the PLED didnt flash as it did before. I didnt get a a picture on the screen though.Re: HP 1955 Monitor Repair Guide<br ...you want there...Leave a comment:
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