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Post by tschaeikaei on Feb 16, 2016 12:25:37 GMT -5
Mastertech, do you mean center convergence on red?
I tried that on both red and blue in all directions yesterday. Worked well, but i did not tweak it to the limit, meaning 0 or 100% of the range.
In the service manual i found that R93 and R96 are both 1/3W 1Ohm. R1001 is 2.2Ohm and the same size so i think it is 1/3W, too.
Am i right there is the full 85V (or maybe a bit reduced under load) flowing through Q20 and the resistors?
So assuming Q20 with an Rdson of 1 Ohm (datasheet tells this) 0.41Ohms 1W of the 3 parallel resistors in series with 0.47Ohms 1W of R97, L2 being in the 0.1Ohms range...
Regards, Julian
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Post by tschaeikaei on Feb 16, 2016 14:06:34 GMT -5
Skip the math, i found some resistors. The board is fully working again.
But still the 3V is not as i think it should be. +3.7 and -4.1V at the worst case.
mod-supply ramps to aobut -120V if the picture is 100% wide.
I'm going to reassemble everything now.
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Post by mastertech on Feb 16, 2016 15:34:14 GMT -5
Good job. I had assumed you had checked those resistors based on your post but I guess I should not be assuming.
As far as those 3v readings, that supply is for red and blue centering based on the schematic. This would not be convergence. But I do not know how the Marquee uses this centering (a menu control or automatically based on scan rate) so you have to determine that. If the centering is working properly, I would not worry about the "off" readings. However, if you determine there is an issue it would be the first place to look.
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Post by tschaeikaei on Feb 16, 2016 18:13:17 GMT -5
I must have had a false reading on the meter because they were still in the circuit when i measured them the first time. After Gjaky asked me again about them i desoldered one pin of each resistor and got an infinite resistance reading. Too bad, sometimes i feel like a real idiot  It was the first i measured (after seeing R1001 blown) and noted them "ok" on my checklist. I reassembled the projector and everything seems fine. Going on with the setup tomorrow. Could i still get an answer on how fast Q20 has to switch? I like the idea of replacing it with another mosfet with less Rds on to be sure it doesn't blow again. Regards, Julian |
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Post by gjaky on Feb 17, 2016 1:03:40 GMT -5
I think you can use the IRF730 safely instead of the original.
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nashou
Unmoderated Off Topic
Tech in Training.....
Posts: 1,239 
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Post by nashou on Mar 3, 2016 14:54:42 GMT -5
The centering circuit is based of the incoming sync signal automatically, I believe this comes from the DPB on the CLM. This does affect Convergence as far as the starting point for the center.
Those 3300uf 6.3 caps are also very important to stability there.
nashou
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Post by gjaky on Apr 7, 2016 15:44:01 GMT -5
Just found this:
tse:
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Post by tschaeikaei on Apr 10, 2016 10:26:43 GMT -5
I did the repair three times and advised a guy who had the same fail over on CP.
What i found is: You got to use the IRF730, i took a 740 and it blew after some 10min.
It comes down to the niput/output capacitances of the Mosfet.
I drilled and tapped a hole into the lower section of the big heatsink and mounted the IRF
to it using some cables to connect it to the board.
Has been working good since i did that.
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It was the first i measured (after seeing R1001 blown) and noted them "ok" on my checklist.
