| Author |
Message |
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 11:05 am Post subject: |
|
|
Ok I would like to measure the burst signal on M4. It comes from the hybrid amplifier that is fed with 190V. Black is close to 190V I think.
So if I set low contrast I would have a signal going between 190V and 100V or so.
If I use a voltage devider network with 1 MOhm resistors getting it down to 20 V or so than would that be possible using a 15pF probe?
M9 seems to be a grounding point.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
 |
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 11:46 am Post subject: |
|
|
removed something was wrong I have not seen this amount of peaking again.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
Last edited by redfox001 on Tue Feb 16, 2016 4:57 pm; edited 1 time in total
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 11:57 am Post subject: |
|
|
With or without probe.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 12:24 pm Post subject: |
|
|
It might be that this is the peaking moome added and that the rest of the video is actually very good compensated by Barco.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 12:40 pm Post subject: |
|
|
I feel like putting my 909 on the ceiling again. This must look much better that the last time I had it working with my cinemax. I just love the perfection of the rest of this machine. A very little roll off is not or hardly visible.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 3:54 pm Post subject: |
|
|
I changed the peaking a bit and mainly the 2 pixels seem more even now might be hard to squeeze more out the 1 pixel lines.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Tue Feb 16, 2016 4:02 pm Post subject: |
|
|
| Quote: | | I do not know why but removing the probe does not change the lightness of the bars on the tubeface |
Thats because of the low impedance of the circuit, the op amp can drive the probe without problems.
And dont even think about measuring the hybrid driver output. Really.
Try a online RC lowpass calculator. You will see that you need a resistor in the kiloohm range, and due to the high voltage this becomes a problem. You can decouple the DC part, but even with a 1pf probe this is complicated. With a 10 pf probe you are lost.
I removed most peaking components on the driver and switcher, maybe thats gives me the linear response. Will try original boards later. The picture looks a lot better without all the peaking. That are simple RC filters, they also affect low frequencies.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 5:00 pm Post subject: |
|
|
I remeasured m204 before the hybrid and something went very wrong. The peaking I saw earlier is gone. I do not know what happened but now I get the same response I also got from the driver and that makes more sense. Not much changed in the picture so it was wrong measurement or something.
Also the peaking on the driver does not work like I figured have to experiment a little more.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 5:03 pm Post subject: |
|
|
One other thing. In my menu's I have the option driver voltage and it is set to 35V it can go much higher and I do not know what it means.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 5:14 pm Post subject: |
|
|
| the dude wrote: | | Quote: | | I do not know why but removing the probe does not change the lightness of the bars on the tubeface |
Thats because of the low impedance of the circuit, the op amp can drive the probe without problems.
And dont even think about measuring the hybrid driver output. Really.
Try a online RC lowpass calculator. You will see that you need a resistor in the kiloohm range, and due to the high voltage this becomes a problem. You can decouple the DC part, but even with a 1pf probe this is complicated. With a 10 pf probe you are lost.
I removed most peaking components on the driver and switcher, maybe thats gives me the linear response. Will try original boards later. The picture looks a lot better without all the peaking. That are simple RC filters, they also affect low frequencies. |
Indeed the probe can still be removed with no change but the peaking that I measured is now gone when I measure again. Perhaps a bad grounding? The second time I used the grounding point on the board.
We can make a dc from the ac but than we would need a full 1 pixel pattern full 2 pixel pattern etc.
But measuring the hybrid output is not the most important thing. We can check the screen for that.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
Last edited by redfox001 on Tue Feb 16, 2016 5:25 pm; edited 1 time in total
|
|
| Back to top |
|
|
MeV
Joined: 16 Nov 2015
Posts: 26
Location: Germany
|
| Posted: Tue Feb 16, 2016 5:16 pm Post subject: |
|
|
| redfox001 wrote: | | One other thing. In my menu's I have the option driver voltage and it is set to 35V it can go much higher and I do not know what it means. |
Driver voltage is for your convergence board. Higher Voltage -> more range for convergence correction. Barco recommends to set this voltage low as possible where you see no distortion on the screen, so heat dissipation by convergence amp is recuded.
| Description: |
|
| Filesize: |
88.21 KB |
| Viewed: |
3964 Time(s) |
|
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 5:26 pm Post subject: |
|
|
| MeV wrote: | | redfox001 wrote: | | One other thing. In my menu's I have the option driver voltage and it is set to 35V it can go much higher and I do not know what it means. |
Driver voltage is for your convergence board. Higher Voltage -> more range for convergence correction. Barco recommends to set this voltage low as possible where you see no distortion on the screen, so heat dissipation by convergence amp is recuded. |
Ok thanks! nothing to with the video I see.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Tue Feb 16, 2016 6:21 pm Post subject: |
|
|
Huh, that can be adjusted? Cool... The 1209 has also a variable convergence driver voltage, but it is controlled by the input frequency.
The overshoot could be caused by ringing due to inductance in the ground connection. Did you connect it to the chassis ground? I connected by scope ground to the heatsink wich apears quite direct since it is connected to the amp board ground plane. Maybe i should try that ground point also.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 6:24 pm Post subject: |
|
|
Last time I used the ground point on the board. Nice to see how they have several points where you can simple connect a probe by the way. First time I used the heatsinc. With the impedance something weired happened.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Tue Feb 16, 2016 6:57 pm Post subject: |
|
|
Nothing changed, still linear. But that was to be expected since the ringing was in the first 2 bursts.
The probe capacitance and the ground inductance form a resonant LC circuit. You can minimize the effect by soldering a grounding clip for your probe direct to the board where you can connect the probe, the small ring above the probe tip provides a grounding for that.
In my pic you can see a 2. amplitude that is caused by the oscillations in the first 2 bursts as a brighter area. Therefore a old analog scope is still the best thing to have for this kind of stuff, you see details that the digital one don't show because each pixel has the same brightness. And you can get them quite cheap, even such a bandwidth monster like my tek (wich was a very high end scope back in the good old analog days).
Last edited by the dude on Tue Feb 16, 2016 8:10 pm; edited 1 time in total
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 7:37 pm Post subject: |
|
|
Ok I was searching in that direction does this tektronic work with one of those fet probes too? Thanks for the tip! I will get me one right away.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Tue Feb 16, 2016 8:04 pm Post subject: |
|
|
I only have passive probes. Unfortunally.
Every scope can work with active probes as long as it provides internal 50 ohm termination. Some probes can be terminated at the connector box (seen that for philips for sure), but internal would be better i guess. Most probes expect power supply from the scope and when you have a scope that doesn't support it or is a different brand, then you need some external power also. My scope has a extra connector on the BNC inputs, but i think thats only for detecting the probe type (1x or 10x).
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 8:09 pm Post subject: |
|
|
Found p6201 not to expensive
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Tue Feb 16, 2016 8:14 pm Post subject: |
|
|
I think the difference between your and mine is the moome. It peaks a little more than the hdfury. My scope does not show it.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Tue Feb 16, 2016 8:15 pm Post subject: |
|
|
Be sure to get all the required stuff like divider heads and psu.
And there is one draw back: The active probes are not as universal as passive ones. They have a VERY limited voltage range (few volts) and can be destroyed when exceeding it.
|
|
| Back to top |
|
|
|
|
