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picree
Joined: 31 Mar 2006
Posts: 351
Location: Johnson City, TN
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| Posted: Sat May 03, 2008 3:38 pm Post subject: Setting RGB Output Amps, BG808 "Yeah, I messed with the |
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I was having a minor problem setting blue bias on my BG808. I always had too much blue and had to lower the setting to around zero. So I started messing with the RGB output amps. I have a scope I'm using to set them but I'm having a hard time getting them set such that my R&B bias/gain settings for 6500K are comfortably in range.
I carefully read the manual and followed it precisely. Using an input of black=2.0v and white=4.35v I set each of the amps to output black=185v and white=85v. According to the scope, I can get both the input and output signals dead on their values but I find that the R&B bias/gain settings are either way off or very close to maxed out leaving no room for tweaking gray scale.
It seems like the ABL jumpers might be part of the problem. After adjusting the amps you have to replace the ABL jumper. Sometimes, when replacing this jumper the color on the screen shifts dramatically and other times it barely changes. Has anyone else seen problems with the ABL circuits and black level color temperature problems?
Does anyone else have a better way to set these amps? It's about to drive me nuts!
_________________
MAIN THEATER: (JVC RS2000; Yamaha UDP-LX500; Yamaha RX-V2400; Lumagen Radiance Pro, Vertex)
SECOND WII-ATER: (BG808; WII; Oppo 971H; Moome external box; BG-DVI transcoder; tse gamma box; Extron)
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Tom.W
Joined: 09 Mar 2006
Posts: 6635
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picree
Joined: 31 Mar 2006
Posts: 351
Location: Johnson City, TN
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| Posted: Sat May 03, 2008 10:57 pm Post subject: |
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Thanks for the link Tom but no, I read it through and it didn't say anything about the amps. I think he fixed it with a HTPC...which I don't have as an option. 
I'm getting closer but I have to flatten the green amp out a bit (lower the black voltage by five volts and raise the white voltage by five volts). That seems to help but I would rather them be at spec.
Anyone else mess with their amps? Are the instructions in the BG808 manual the best way to set these amps?
_________________
MAIN THEATER: (JVC RS2000; Yamaha UDP-LX500; Yamaha RX-V2400; Lumagen Radiance Pro, Vertex)
SECOND WII-ATER: (BG808; WII; Oppo 971H; Moome external box; BG-DVI transcoder; tse gamma box; Extron)
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Sun May 04, 2008 7:18 pm Post subject: |
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You have to measure and adjust input signal separately to every amp, because every color have different gain settings in driver board. Usually it's needed to adjust contrast little differently for every color to get that 4.35 Vpp input. That way you get all amps calibrated similar way, color balance is adjusted in driver board not with these amp pots.
If problem remains, then problem need to fix from driver board pots or leave abl jumper out.
I have one extra set of abl removed amps, if you like to test those some day. Customs makes possible swap little difficult...
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picree
Joined: 31 Mar 2006
Posts: 351
Location: Johnson City, TN
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| Posted: Mon May 05, 2008 1:44 am Post subject: Of what use is ABL really? |
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| Ile wrote: | | You have to measure and adjust input signal separately to every amp, because every color have different gain settings in driver board. Usually it's needed to adjust contrast little differently for every color to get that 4.35 Vpp input. That way you get all amps calibrated similar way, color balance is adjusted in driver board not with these amp pots. |
Yes Ile, my post was brief but, each amp is adjusted separately for the 4.35 Vpp input. The 2.0 V setting is usually off a little bit as well but tweaking them gets them right on. Before setting the output voltages I make sure that the input voltages are right on spec for each amp. The output voltages are also exactly at spec too when I'm finished.
It just seems like the green tube has too much range for the voltage settings...I have too little green at the black end and too much green at the white end. I have a couple of spare, never-touched, amps I will swap out but I think I've done this before with no luck. Could it be something with the green tube or the neck card or the HV lead?
| Ile wrote: | | I have one extra set of abl removed amps, if you like to test those some day. Customs makes possible swap little difficult... |
Thank you very much for your offer but, to save trouble, I should try to get these to work. I still have your "ABL Removal" schematic and may modify my own if that seems like the right thing to do. I think you said that to get rid of streaking you had to completely remove the ABL circuit (that I remember). But what effect will it have to just remove the jumper? Will the black level wander?
_________________
MAIN THEATER: (JVC RS2000; Yamaha UDP-LX500; Yamaha RX-V2400; Lumagen Radiance Pro, Vertex)
SECOND WII-ATER: (BG808; WII; Oppo 971H; Moome external box; BG-DVI transcoder; tse gamma box; Extron)
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Mon May 05, 2008 11:53 am Post subject: Re: Of what use is ABL really? |
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| picree wrote: | It just seems like the green tube has too much range for the voltage settings...I have too little green at the black end and too much green at the white end. I have a couple of spare, never-touched, amps I will swap out but I think I've done this before with no luck. Could it be something with the green tube or the neck card or the HV lead?
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Maybe green tube is chanced to new in some point and that causes problem. Or decoder/driver board gain calibrations are drifted.
| picree wrote: | | But what effect will it have to just remove the jumper? Will the black level wander? |
ABL won't affect to black level setting when jumper is removed.
Black level shouldn't wander in few thousand hour period, so you don't need to adjust G2 levels every night. 
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picree
Joined: 31 Mar 2006
Posts: 351
Location: Johnson City, TN
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| Posted: Mon May 05, 2008 6:38 pm Post subject: Compensating for a new green tube...maybe? |
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| Ile wrote: | | Maybe green tube is chanced to new in some point and that causes problem. |
Well, yes indeed I changed the green tube out last year. I didn't notice any difference before. The problem has just come up because I bought a calibration tool and software (HCFR). I suppose the only solution would be to tweak the green output voltages a bit to compensate. Instead of 100 V for the black to white range I tried 90 (BL=180 v and WL=90 v). That seemed to help a little but then after readjusting G2's it was still the same (too much blue on the low side). I will try maybe a voltage range of 70 volts? Will that hurt anything or do you know of a better way to compensate for this?
| Ile wrote: | | Or decoder/driver board gain calibrations are drifted. |
I didn't think decoder/driver board would affect the output amps. It does? Don't we set the output of the amps based upon a fixed input voltage (2.0 and 4.35)?
| Ile wrote: | | Black level shouldn't wander in few thousand hour period, so you don't need to adjust G2 levels every night. |
Then I suppose maybe I'll try running without the ABL jumper and just keep an eye on G2's so I don't accidentally burn up a tube should it wander. ABL seems to be jumpy/touchy anyways.
_________________
MAIN THEATER: (JVC RS2000; Yamaha UDP-LX500; Yamaha RX-V2400; Lumagen Radiance Pro, Vertex)
SECOND WII-ATER: (BG808; WII; Oppo 971H; Moome external box; BG-DVI transcoder; tse gamma box; Extron)
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Tue May 06, 2008 10:51 am Post subject: Re: Compensating for a new green tube...maybe? |
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| picree wrote: | | I didn't think decoder/driver board would affect the output amps. It does? Don't we set the output of the amps based upon a fixed input voltage (2.0 and 4.35)? |
Yes we calibrate output amps with "fixed" input voltage, but that is just to make them identical. In normal operation rgb amp inputs are not identical. Contrast setting chance driver board output Vpp (rgb amp input) and R/B white gain just one color Vpp.
For example contrast at 100, driver outputs should be
3200K R 3.8 Vpp, G 4.0 Vpp, B 2.6 Vpp
6500K R 3.6 Vpp, G 4.0 Vpp, B 3.4 Vpp
9300K R 3.6 Vpp, G 4.0 Vpp, B 3.8 Vpp
Now you see why green tend to worn out first. 
As you probably have been noticed color balance settings in menu are just presettings for custom gain settings. So use custom settings if those have range and if not then turning green Vpp to little smaller (driver P1) would be easiest thing to do.
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picree
Joined: 31 Mar 2006
Posts: 351
Location: Johnson City, TN
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| Posted: Thu May 08, 2008 12:18 am Post subject: Re: Compensating for a new green tube...maybe? |
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| Ile wrote: | Now you see why green tend to worn out first.
As you probably have been noticed color balance settings in menu are just presettings for custom gain settings. So use custom settings if those have range and if not then turning green Vpp to little smaller (driver P1) would be easiest thing to do. |
Aaah! Thank you for that bit of insight! I will recheck the driver board and see if they are to spec. If not I will lower green (P1) as you suggest. (I assume you mean P1 on the driver board and not on the green output amp.)
As always thanks for your most useful help! 
_________________
MAIN THEATER: (JVC RS2000; Yamaha UDP-LX500; Yamaha RX-V2400; Lumagen Radiance Pro, Vertex)
SECOND WII-ATER: (BG808; WII; Oppo 971H; Moome external box; BG-DVI transcoder; tse gamma box; Extron)
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Thu May 08, 2008 7:39 am Post subject: Re: Compensating for a new green tube...maybe? |
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| picree wrote: | Aaah! Thank you for that bit of insight! I will recheck the driver board and see if they are to spec. If not I will lower green (P1) as you suggest. (I assume you mean P1 on the driver board and not on the green output amp.)
As always thanks for your most useful help! |
Yes, P1 on driver board. I have calibration procedure for this if you need it. Full calibration is bit pita to make without riser card though.
It could be that it's on specs and you still have to lower green little, because your new green tube have more light output than R/B.
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