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Post by tschaeikaei on Dec 15, 2015 7:49:19 GMT -5
I'm still a bit disappointed that the vcc voltages,
especially 15 and -15v are so much off from nominal.
Is this normal? I'm going to crosscheck with the other projector.
But afaik, they come directly from the LVPS.
Have to check for bad solder connections or worn out capacitors maybe.
As far as I recognise, ripple was about 0.1V which I think is not too bad
but improvable.
What do you think?
Regards, Julian
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Post by Deleted on Dec 15, 2015 13:46:45 GMT -5
There is this mod where coils are placed on the powerlines. It really helps. When you see the Barco 909 there are coils on the powerlines of the focus, the astig, the convergence. Barclay noticed this in the marquee performance thread on Curts and did that on his Marquee too. Lowers noice greatly. Do you know that focusboard thread? I have coils on my focusboard, on my convergence board and on my vertical board. Think I should look at the astig once. Focus Board Mod |
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Post by Deleted on Dec 15, 2015 13:56:24 GMT -5
Oh by the way your video was great. I realise I repaired my focusboard looking and measuring components only. Some life measurements will be fun but I do think most measurements could be done with a multimeter too as MT said so.
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Post by Deleted on Dec 15, 2015 14:06:44 GMT -5
Here is a picture of my coils on the convergence board. I actually have the board shown in the picture and it lowered noise. Look at post by mp. Conv Board Coils |
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Post by mastertech on Dec 15, 2015 21:00:27 GMT -5
I'm still a bit disappointed that the vcc voltages, especially 15 and -15v are so much off from nominal. Is this normal? I'm going to crosscheck with the other projector. But afaik, they come directly from the LVPS. Have to check for bad solder connections or worn out capacitors maybe. As far as I recognise, ripple was about 0.1V which I think is not too bad but improvable. What do you think? Regards, Julian Yes, I noticed that also. Have you checked those +/-15V lines again since the repair? |
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Post by tschaeikaei on Dec 29, 2015 18:11:10 GMT -5
Late answer: I tested the +-15V again, not at the FGM itself, it is hardly accessible now, because I've bolted it into its metal cage for better heattransfer.
But I checked at the astig board connector and the multipin connectors at the VNBs. +15,1V vs. -14,9V.
Not exactly perfect, but seems ok.
Regards, Julian
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Post by mastertech on Dec 31, 2015 15:39:23 GMT -5
Yes, that is much better.
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Post by tschaeikaei on Feb 15, 2016 15:11:51 GMT -5
Oh and again i broke something.
During a mechanical setup i left the HDM uncooled.
The main heatsink didn't get hot but Q20, the only part on the board having his own heatsink, said puff.
Everything went dark, h-fail, i took the board out stole some parts from another HDM and finally got it to work again.
Everything works but the main width setting (PIC-2 in the on screen menu).
Strange thing is: if i start at picture width 0%, ramp up to 100%, everything behaves normal till about 90%, then only the number increases, the picture doesn't grow any wider.
If i decrease from 100 to 0%, nothing but the numbers change between 100 and 65, then all of a sudden the picture shrinks and everything between 65 and 0% is again as it should be.
What i changed so far:
Q20, R62, D21, D22, R1001.
All these because of the initial fail of Q20. The resistors are meant as fuses and were ...exploded.
I checked a quiete large numbers of parts including everything in the modulator circuit (right side third of page 3).
After realizing the width setting did not work properly (i had reassembled the projector completely at that point),
disassembled erything again, took the HDM out and tried another HDM, another daughter board (HDB) and so on.
I can definitely say that it is the HDM itself, not the daughter board or any other part of the projector.
Then i changed U17 and U20 on the HDM and tried again. As it was, strange behavior of the width setting.
Key and Pin seem to work well, besides i did not ramp them up fully to 0 or 100%.
The next part i would change could be the multiplier circuit U18, but i don't like the idea of changing countless parts.
In addition, i cannot measure anything on the live HDM, because the projectors are both at the ceiling and i don't have anything
to keep the loose boards in place while running.
So will you help me again? Remember i have two other HDMs here, one of them working and the other partially harvested.
Thank you in advance, Julian
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Post by gjaky on Feb 15, 2016 15:36:18 GMT -5
Your problem is with the local power supply for the H-output circuit, try to change U2 and look the parts around it. This power supply should give a proportional output voltage with picture width and scan frequency, but as you say it's barely working, I guess the blown up Q20 took the feedback circuit too (that is U2), in worse case, you might have to change U3 and (or) U12 too.
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Post by tschaeikaei on Feb 15, 2016 19:00:36 GMT -5
Thank you Gabor. I don't understand at all what U2 is doing, but i'm going to follow your instructions and change it. I still had the old Q20 laying around and tested it again. 32Ohms between source and drain in either direction, no continuity from gate to one of the other pins. Even checked with the lab power supply, 35V from gate to the other two pins... no current flow in any direction. Do you agree with me that U12 has to be on the safe side? Oh and could you tell me what frequency does Q20 switch? I saw this thing has a Rds on of 1 Ohm, what lead me to the guess that i should use another MOSFET with smaller resistance here. Should improve temperature problems. cdn-reichelt.de/documents/datenblatt/A100/IRF730_FSC.pdfIRF 730 is the same part as MTP5N40 as it is called in my schematic. I'm going to test the board again in the projector now after i did change U2 and made sure everything discrete around is ok. Will report back in a few minutes. Thanks! Julian No, still the same. |
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Post by mastertech on Feb 15, 2016 19:31:37 GMT -5
If you want to see if that supply circuit is now running properly just test the + and - 3v supply rails. You can worry about the "mod-supply" after testing the 3v supply.
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Post by tschaeikaei on Feb 16, 2016 11:18:08 GMT -5
Ok, i did solder some wires onto the board and measured the voltages.
Percentage values stand for PIC-2 width settings
+3V measured at C40: 3.4V 0-100%
-3V at C39: -3.68V at 0%, falling to -4V at 100%
mod-supply: -80V at 0%, linear falling to -102V at 66%, 97V at 100%
ground for all measurements between C39 and C40
Regards, Julian
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Post by gjaky on Feb 16, 2016 11:54:57 GMT -5
R93, R96 are holding their value firmly?
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Post by mastertech on Feb 16, 2016 12:06:47 GMT -5
Does red centering work properly? You can monitor the +/-3v while adjusting this.
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Post by tschaeikaei on Feb 16, 2016 12:16:00 GMT -5
Ha! 100 points for Mr. Gjaky! Both of them open connection.
Although they look like new out of the box. This is really annoying because that part of the circuit was the first i checked.
I don't have 1 Ohm resistors here, could you tell me if i could use a fuse instead and what value it should have?
I will replace R93, R96 and R1001 all together with it. Those 0.41 Ohms should not matter to much, should it?
Thank you, Regards, Julian
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