| Author |
Message |
mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
|
| Posted: Fri Feb 12, 2016 8:48 pm Post subject: |
|
|
| redfox001 wrote: | Yes he is wrong was probable fired at barco lol  Now trying to impress people with the fact that he needed 20 year of trial and error... |
|
|
| Back to top |
|
 |
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Fri Feb 12, 2016 8:53 pm Post subject: |
|
|
You said something like 'The 1209s neckboard uses a RF switch (DG542) for ABL reference switching.'
Doe the 1209 neckboards hold inspiration for the abl or g2? I have not looked into it. Seems you played with the abl over my head.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Fri Feb 12, 2016 9:19 pm Post subject: |
|
|
The 1209s ABL reference voltage circuit might work i guess. The 1209s does not regulate G2, it is fixed. Instead the blacklevel is controlled by the rgb driver only (this was the reason for beeing unsure if the 909 board will work in a 1209s). But the 1209s needs a reference also, and this is generated by a omp amp buffer (thats DC only) and there is a fast RF switch.
This is the ABL Ref/switch part, its directly at the video input:
| Description: |
|
| Filesize: |
17.86 KB |
| Viewed: |
8013 Time(s) |
|
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Fri Feb 12, 2016 9:30 pm Post subject: |
|
|
|
Q16 seems to be for switching between leakage measurement and ABL measurement, the ABL Pulse generation is almost the same as the 909 circuit.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 3:31 am Post subject: |
|
|
| the dude wrote: | | Oh, and one comment more on the "black level": The 2. op amp is for changing phase in the first place. Also it adds a DC offset to the video, and thats *NOT* for black level even if the pot is named "black level". Its for adjustment of the *voltage* level for black, eg. the "cut of voltage" (the cathode drive voltage when the screens just turns black), as the ABL regulates the black level and any DC offset would cause a compensation through the ABL loop. So this pot is adjusted to ensure the cathode is driven at 185V at cutoff, in fact this pot also sets G2. Also a very important setting that has nothing to do with video signal levels. |
As I understand it first the blanking pulls the opa to blacker than black. At that time the leakage is measured of the tube. After that blanking and q202 puts a reference black on the video and the abl voltage is measured to regulate the g2.
Now without opa the leakage measurement gives no problem even if the tube is leaking?
And the reference black during blanking from q202 is all wrong so the g2 is regulated all wrong too.
Perhaps this could be recalibrated with the black level pot? But perhaps the blanking pulls the video to much negative.
I tried to recalibrate with the pot but nothing changed.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 3:55 am Post subject: |
|
|
we really need that blacker than black on the video during blanking. So opa has to stay. Back to the ad835?
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 10:28 am Post subject: |
|
|
| Quote: |
As I understand it first the blanking pulls the opa to blacker than black. At that time the leakage is measured of the tube. After that blanking and q202 puts a reference black on the video and the abl voltage is measured to regulate the g2.
|
You got it
| Quote: |
But perhaps the blanking pulls the video to much negative.
|
Exactly. It is -9V, this will drive the output to +8V. Maybe it would work when we make the blanking switch voltage adjustable.
Anyway, i don't like this circuit. It uses 2 amps for a something that can be done with a switch. Also it is a little bit tricky.
I think its must be possible to use the 1209s circuit on an little extra board for abl switching. The ABL_MEAS and ABL_LEAKAGE pulses exists in the 1209s to. Maybe no further amplification is required so the HFA1100 may be unnecessary to, maybe the cut off voltage will be in a usefull range to without adjustment. I never turn constrast to max, so not all the gain is needed.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 11:02 am Post subject: |
|
|
Yes but those switches can be bandwidth limitations too. They write about this blanking that it should provide good bandwidth so they put some thaught in it. What do we know about that dg542? Switch? 500 MHz.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 11:15 am Post subject: |
|
|
Making blanking voltage adjustable might be the option? It should pull to around +4V.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 11:16 am Post subject: |
|
|
Ah I was going to check that and yes there are more better switches that can be used.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 11:18 am Post subject: |
|
|
Hmm, we can't use the fast switch, the datasheet says:
| Quote: | | All RF connections must be DC blocked or held at 0V DC |
Hmm. Maybe making the blanking voltage adjustable is the better way.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 11:34 am Post subject: |
|
|
Ok that might be why the marquee uses a switch that switches between video and clm (controller) and during blanking the controller puts a signal on the z input of the ad835 establishing blacker than black. If I am right. So theynuse one switch for menus and blanking and the ad835 for black that is efficient.
We have a switch on the switcher for the menus than blanking is generated on the driver and applied on the rgb output.
now we have to get black on the video without the opa. Yes if we can adjust level during blanking that seems simplest.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 11:42 am Post subject: |
|
|
|
Maybe we can put a pot on the noninverting input and pull it against +8V with a PNP transistor during blanking. This would also allow removal of Q200 and Q201 from the input.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 12:19 pm Post subject: |
|
|
A question for my understanding. How important is that leakage measurement? I do not see it on the marquee. They only measure ibcl and that is something different to my understanding.
Than if we adjust the g2 manual with a pot why do we need exact +4V or more on the video during blanking? If the video is to black lets say 8V is that a problem during blanking when nothing is measured or sampled? Has that to do with the cut off?
That way a lot of stuff can be pulled even the measuring stuff limits bandwidth.
Might be I am missing something here 
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 12:31 pm Post subject: |
|
|
| the dude wrote: | | Maybe we can put a pot on the noninverting input and pull it against +8V with a PNP transistor during blanking. This would also allow removal of Q200 and Q201 from the input. |
Eh ok. What happened with my 5166 when the inverting input was drawn to -9V I thought you said it was drawn to the positive rail 8V? Ah misunderstanding it was drawn to the negative I think.
Ok I get it. So exact regulation between 4V and 8V is not mandatory?
Finally I get what happened to my 5166 it was pulled to -8V during blanking
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
Last edited by redfox001 on Sat Feb 13, 2016 12:42 pm; edited 1 time in total
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 12:39 pm Post subject: |
|
|
| Quote: | | Than if we adjust the g2 manual with a pot why do we need exact +4V or more on the video during blanking? If the video is to black lets say 8V is that a problem during blanking when nothing is measured or sampled? Has that to do with the cut off? |
As i understand it: During vertical retrace the blanking signal is active. The output of the opamp can be any value that cuts of the beam for sure, the actucal voltage is not important. At the end of this period the vertical deflection applies a "overshoot" pulse that deflects the beam out of the raster. Then the IBCL line is triggert. Now leakage and more important the beam current is measured. The video level needs to be raised just a little bit above cut off in order to measure beam current. The measured value is captured with a hold-and-sample circuit and used to adjust G2 for a dark beam current of about 10nA. So during ABL the video level must be at that reference voltage. R180, R220, R221 and the input impedance of the inverting input of I201 form a voltage devider network when Q202 starts conducting. This is the reason why the blanking voltage is important. So if the output voltage during blanking will be 8 V, the reference voltage is only a little bit lower and therefore much to high for ABL measurement. But if i think about it i would expect the g2 regulator to drop g2. Hmmm.
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 12:47 pm Post subject: |
|
|
Now i understand it. A to high positive voltage will cause total cut off, and because of that G2 is pushed to the max. The inverted logic is a little bit confusing.
Edit: Without a little DC offset from the 2. stage the ABL reference would be still negative. So this offset is required also.
|
|
| Back to top |
|
|
redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
|
| Posted: Sat Feb 13, 2016 1:00 pm Post subject: |
|
|
Ok one more thing that is bothering me when I look at the opa the white clamp is with the voltage divider close to 3 V or so and the black clamp is close to 6 V or so. So if my 5166 was pulled to -9 V it was putting out a hell of a light. So the retrace lines should be very bright. I think the g2 was pulled to the max to save me?
It cant go below -2V.
_________________
701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
|
|
| Back to top |
|
|
the dude
Joined: 11 Sep 2013
Posts: 179
|
| Posted: Sat Feb 13, 2016 1:08 pm Post subject: |
|
|
|
Huh, this circuit ist tricky.. the voltage devider at the noninverting input would cause a DC offset also.
|
|
| Back to top |
|
|
|
|
