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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 8:32 pm Post subject: |
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Im meant the emitter peaking network on the neckboard. But this is some kind of magic...
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redfox001
Joined: 16 Mar 2009
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Location: The Netherlands
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| Posted: Mon Feb 15, 2016 9:18 pm Post subject: |
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No idea. How would we measure at the outside of the hybride? The voltages are to high but perhaps very low contrast? Or making a voltage devider?
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redfox001
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| Posted: Mon Feb 15, 2016 9:21 pm Post subject: |
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I think I will be going through m200 m203 m202 on the output board.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 9:28 pm Post subject: |
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M204 would be of interest to. I will check that tomorrow.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 9:38 pm Post subject: |
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One note on high voltages: The cathode voltage will be max. at black! Thats negative logic, the cathode is pulled to ground and should be +85V at max. brightness.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 9:41 pm Post subject: |
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The emitter has positive logic, but i think measurements at this point would not show anything usefull.
Edit: Not sure about this...
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redfox001
Joined: 16 Mar 2009
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| Posted: Mon Feb 15, 2016 9:51 pm Post subject: |
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| the dude wrote: | | One note on high voltages: The cathode voltage will be max. at black! Thats negative logic, the cathode is pulled to ground and should be +85V at max. brightness. |
Ok carefull there.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 10:35 pm Post subject: |
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I was just too curious about it, so i did the test.
This time the good news is bad, the signal is perfect at M204. Even if the scope would lie a litte and has a overpeaked response (i don't think so) this would be the same for the same frequency.
So we have a full drive signal at the input of the hybrid. The bottleneck is found, but this would be hard to fix.
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redfox001
Joined: 16 Mar 2009
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| Posted: Mon Feb 15, 2016 10:58 pm Post subject: |
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Ok two options. One compensating. My moome is allready doing that and it looks good. If you compensate and get a flat responce there is no problem I think. Or two Gjaky's hybrid project.
But we have not the same results and that is strange. In my case before the driver there is peaking and after there is a roll off. My vertical lines are not so dark indicating that the roll off does not get much worse in the neckboards.
You have a flat response from the driver and worse vertical indicating that there is much roll off in the neckboards ???
Could there be a difference in powersupply between 1209 and 909?
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the dude
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| Posted: Mon Feb 15, 2016 11:06 pm Post subject: |
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I don't believe that peaking can help much. It only makes the video worse. And when we peak it, it should be done at the emitter of the hybrid.
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redfox001
Joined: 16 Mar 2009
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| Posted: Mon Feb 15, 2016 11:06 pm Post subject: |
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| the dude wrote: | | I don't believe that peaking can help much. It only makes the video worse. And when we peak it, it should be done at the emitter of the hybrid. |
It makes it worse if there is overshoot somewhere. If the response is flat it is just like probe compensation. It is done on the marquee to on several places as they should.
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redfox001
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| Posted: Mon Feb 15, 2016 11:08 pm Post subject: |
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I think what you mean is ringing. That looks bad. It happens when you sharpen with software in the wrong frequencies.
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the dude
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| Posted: Mon Feb 15, 2016 11:09 pm Post subject: |
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Supply voltage is +210V in both machines.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 11:14 pm Post subject: |
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Maybe we should bypass the useless evil OPA with a straight wire. With some other voodoo this would give a nice inverted video with 500+ Mhz response for sure 
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redfox001
Joined: 16 Mar 2009
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Location: The Netherlands
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| Posted: Mon Feb 15, 2016 11:22 pm Post subject: |
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Do you have lug tubes.I bet they are designed for lug.
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the dude
Joined: 11 Sep 2013
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| Posted: Mon Feb 15, 2016 11:23 pm Post subject: |
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| Quote: | | It makes it worse if there is overshoot somewhere. If the response is flat it is just like probe compensation. |
At some point there is no further gain to get out of stage and you only peak the lower frequencies because the filter has a some roll off.
If the amp can't deliver enough current to charge the cathode within the given time, it can't.
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the dude
Joined: 11 Sep 2013
Posts: 179
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| Posted: Mon Feb 15, 2016 11:28 pm Post subject: |
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Only blue is LUG. Green is PT22-22 and Red LCP or something like that (hisres, white/white guns). They may have a little bit more capacitance, but not that much. I also have a LUG, but the phosphor of the PT22 is perfect while the LUG has a little bit of wear (but its well useable) and it is in the wrong housing. It had to be put in a barco scheimpflug housing.
So, enough for today...
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redfox001
Joined: 16 Mar 2009
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Location: The Netherlands
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| Posted: Tue Feb 16, 2016 6:02 am Post subject: |
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I want to do a measurement after the hybrid to realle see the drop and take the scope from the equation. How to do that? Using the rail as ground?
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the dude
Joined: 11 Sep 2013
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| Posted: Tue Feb 16, 2016 6:29 am Post subject: |
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Forget it!
Not without a active probe. A passive probe will have has much capatitance as the cathode, and this is not a 50 Ohm low impedance line.
You need a voltage devider and a very low capacitance probe, 1pf or so will be fine.
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redfox001
Joined: 16 Mar 2009
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| Posted: Tue Feb 16, 2016 10:20 am Post subject: |
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| the dude wrote: | Forget it!
Not without a active probe. A passive probe will have has much capatitance as the cathode, and this is not a 50 Ohm low impedance line.
You need a voltage devider and a very low capacitance probe, 1pf or so will be fine. |
But with a hug voltage devider using mega ohm resistors 1/100 the paracitic load is not so high?
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