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tschaeikaei
Joined: 08 Apr 2013
Posts: 490
Location: Germany/Saarland
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| Posted: Sat Nov 28, 2015 10:42 am Post subject: |
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Hey guys,
I need to know how to set anode cutoff current to match all 6 tubes in max brightness.
There are LCP red PT22-19 and LCP blue in one projector, those 3 use the LCP neckboards, 03-270339-01P. PCB number 50-2039-01P
The other projector uses LPB red and blue and another PT2-19. These use 8500 (180DMB22) neckboards, 03-270338-01P. PCB number 50-2038-01P.
Otherwise, the two projectors are the same.
I've already removed R37 (Pin6 to ground) on the neckboards used with the LPB tubes.
Everything runs good.
But what about different anode current cutoff on 8" and 9"? I need to use the 8" VNBs on 9" tubes and would like to match
all 6 tubes in maximal brightness.
Therefore, I'll have to set R86 higher on the 8" VNBs. But i need to know what values i'll have to measure.
Asked the other way round: What are these pots set to at VDC?
Regards, Julian
_________________
Marquee 9500U edgeblend P43 | NEC 9PG
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sat Nov 28, 2015 12:34 pm Post subject: |
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On 8" tubes the cathode current is limited to 1mA, on 9" tubes the maximum current is 1.4mA if that helps.
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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tschaeikaei
Joined: 08 Apr 2013
Posts: 490
Location: Germany/Saarland
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| Posted: Sat Nov 28, 2015 12:52 pm Post subject: |
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Oh ok, and if setting the potentiometer, is it better to measure on the high side (anode lead) or on the cathode itself?
If measuring on the cathode is needed, i would like to know where exactly.
Helps a lot gjaki, thank you!
Should use full white field and a certain G2/contrast/brightness value when setting R86?
Do 1,4mA fit to any 9" tube, LCP, LPB AND LUG? I could imagine at least LUGs are driven with lower currents?
Regards, Julian
edit: If i interpret the graph on the first page right, this red line is at about 1150mA for LUGs.
But i don't use LUGs, i use LPB and PT22-19. So how do these compare?
http://www.curtpalme.com/forum/viewtopic.php?p=446743#446743
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Marquee 9500U edgeblend P43 | NEC 9PG
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sat Nov 28, 2015 2:29 pm Post subject: |
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| tschaeikaei wrote: | Oh ok, and if setting the potentiometer, is it better to measure on the high side (anode lead) or on the cathode itself?
If measuring on the cathode is needed, i would like to know where exactly.
Helps a lot gjaki, thank you!
Should use full white field and a certain G2/contrast/brightness value when setting R86?
Do 1,4mA fit to any 9" tube, LCP, LPB AND LUG? I could imagine at least LUGs are driven with lower currents?
Regards, Julian
edit: If i interpret the graph on the first page right, this red line is at about 1150mA for LUGs.
But i don't use LUGs, i use LPB and PT22-19. So how do these compare?
http://www.curtpalme.com/forum/viewtopic.php?p=446743#446743 |
I'd rather experiment on the bench with this, in a safe way without tubes and high voltage near.
The current sensing circuit is not voltage dependant. I'd suggest to connect a small voltage on D15's anode say 5V, and terminate the K output with a (variable) resistor in such way to flow ~0-2mA through it.
Feed the VNB with +/-5V and +/-15V but you don't need the +/-85V line. In this way you could check when the over-I signal trips. without causing damage to the tubes / you / the neckboard.
I wouldn't think there is much difference between the different tube types in this regard. Remember also that the HVPS only putting out ~3.4mA (if I am correct) and since the cathode current is flowing into the HVPS you can't actualy drive all three tubes at 1.4mA at the same time because of this. This way it is also possible that the different I max setting between the neckboards cause little practical issues in normal using environment.
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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