Author Topic: Panasonic LCD projector extreme repair  (Read 8568 times)

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Offline Entropia

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Panasonic LCD projector extreme repair
« on: April 10, 2013, 03:56:32 pm »
I recently bought a Panasonic PT-AE900 in non working condition. The seller described that there are red vertical stripes across the screen. It's a classic Panasonic fault, one of the LCD driver ICs overheat causing a few select pins' solder to reflow causing a bridge. The common remedy amongst laymen is just to scrape the bridge off. The person who "repaired" my project obviously used enough force to completely rip off two pins of the driver IC, along with the tinned PCB track. Amateurs... Anyway. The projector powers up, displays image no problem except that red is obviosly f--ed up. I was wondering if it's possible to use a very fine file, sanding paper, Dremel tool or something similar to expose metal from the pins that were ripped off? What's the verdict?

See the attached picture for the horror.
 

Offline mikeselectricstuff

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Re: Panasonic LCD projector extreme repair
« Reply #1 on: April 10, 2013, 04:08:16 pm »
Yes - definitaly doable. being near the corner gives you plenty of space between the pin and the die.
Carefully dremel the plastic down til you hit metal, clean up the dust, apply flux/solder to the pin (solder paste can be good for this) , then lay pre-tinned fine wire along the line of the pin and touch with iron to tack on.   May take a few attempts.
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Offline Entropia

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Re: Panasonic LCD projector extreme repair
« Reply #2 on: April 10, 2013, 06:07:52 pm »
OK, thanks for the tips! I'll try very careful Dremeling first and see where that gets me.
 

Offline SeanB

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Re: Panasonic LCD projector extreme repair
« Reply #3 on: April 10, 2013, 07:58:46 pm »
Don't forget as well to use thermal epoxy and add a heatsink to the toasting IC as well while you are at it.  I have soldered new pins on a side brazed ceramic pacage before, though I did cheat and used 2 stacked turned pin sockets to hold the 2 wires as well, and soldered the other pins into the sockets as well. Was easier than trying to order the obsolete preprogrammed Prom chip anyway.
 

Offline Kaptein QK

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Re: Panasonic LCD projector extreme repair
« Reply #4 on: April 10, 2013, 11:22:48 pm »
Jeebus, that chip looks like it has been attacked by a miniature grizzly-bear!  ;D
 

Offline Psi

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Re: Panasonic LCD projector extreme repair
« Reply #5 on: April 10, 2013, 11:30:24 pm »
I have a PT AE900 as well.
The service manual containing circuit diagrams can be found online. (Let me know if you cant find it)

A few years back i got the vertical stripes problem, however it went away in the 30 seconds while i was looking at it and thinking WTF.
I never saw that problem again.

If you can't get it soldered and buy a new IC instead i would be interested to know how it works.
The service manual says you're supposed to connect the RS232 cable and run service software to tell the projector you have changed IC1053 1055 or 1057. (Dunno why, might be calibration data or chip versions)
And no one seems to have this service software :(

I've done two repair jobs on my AE900.

- Few months after i bought it (2ndhand) the green driver IC (IC1055) developed an internal short on the 5.5V gamma control pin (LCCOM) which feeds the raw green LCD panel.
It was just a static 5.5V which the chip adjusts only when you change the green gamma on the OSD so i just forced it back to 5.5V with resistors to nearby power rails.
I also cut some plastic out of the top and thermal epoxied some bent copper strips as extra heatsinking

http://www.avsforum.com/t/1029165/pt-ae900-no-green-fix-mod-warning-technical

- 5 years later it just switched off while watching a movie and displayed "temp" and "lamp" leds.
After a cool down and reboot it would seem to turn on (light changes to green) but no picture would display. You could see the fans twitch when you hit the soft power button.
I tracked that fault to a open circuit diode on the power board
(The P-Module in the service manual diagram, it was the bottom diode on the cold side).


« Last Edit: April 10, 2013, 11:52:33 pm by Psi »
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Offline peter.mitchell

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Re: Panasonic LCD projector extreme repair
« Reply #6 on: April 11, 2013, 08:47:09 am »
when i do this, i don't cut into the chip, i grind at a very shallow angle, close to the edge, just to take the side off a little, and i use some 30awg kynar wire to solder it, from the chip to wherever.

When soldering, sometimes its a bit difficult to get just the one pin, so i tin the "stub"s and then hot air the 30awg wire to the tinned bit, also, i tend to solder to vias and other component legs, rather than ends of tracks, they just lift again.

a tiny dob of hot glue to hold it in place temporarily while waiting for some thick CA for permanent
 

Offline Entropia

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Re: Panasonic LCD projector extreme repair
« Reply #7 on: April 11, 2013, 06:02:57 pm »
I gotta tell you, when I began I thought this would never work but what do you know... I exposed plenty of copper for me to solder! I'll take the projector to work tomorrow and solder some small wire wrap wire (30 AWG I guess?) on. In the process I managed to also grind one 0402 bypass cap away but I would think the IC survives without. The second to last pin that was broken goes under the chip so I'll have to read the schematics on the service manual to see where that goes and solder the wire directly there. Hope to watch a movie or two in the coming weekend!
 

Offline Things

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Re: Panasonic LCD projector extreme repair
« Reply #8 on: April 12, 2013, 01:29:41 am »
I also have a AE900, although haven't had this issue yet. However the LCD"s have gone out of alignment, so I'll need to buy or make some extension ribbon cables so I can remove the mainboard.

Psi, thanks for the heads up, I'll have a look :)
 

Offline Entropia

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Re: Panasonic LCD projector extreme repair
« Reply #9 on: April 12, 2013, 08:19:18 am »
Soldering was pretty hairy (did it without any microscopes) but it didn't work after all. The vertical stripes remained. I looked up the service manual wondering what the f went wrong, but then I realized I actually soldered the missing VID2 signal accidentally to the RED LCD instead of green. Fixed that in 30 seconds and voila! It works! I couldn't be happier! Thanks for all the tips!
 

Offline Psi

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Re: Panasonic LCD projector extreme repair
« Reply #10 on: April 12, 2013, 09:13:46 am »
I also have a AE900, although haven't had this issue yet. However the LCD"s have gone out of alignment, so I'll need to buy or make some extension ribbon cables so I can remove the mainboard.

Psi, thanks for the heads up, I'll have a look :)

I have a slight alignment issue as well. I talked to some of the service guys on AVS forum and they told me you cant adjust the individual panel alignment. There's no alignment screws.  Each panel is fixed mounted to plastic pins with 4 rubber o-rings.

Alignment issues maybe caused by distorted o-rings but they thought trying to fix/replace them would probably make it worse.
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