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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Tue Jan 08, 2008 2:49 am Post subject: Problem with Barco Retro 400 on high APL scenes |
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Hey everybody,
First off, a big thanks to Clarence for giving me this e-frikkin-normous retro; it might be old but it's sweet!
Down to business - the retro works great until a high APL (average picture level) scene comes up, at which point some of the electronics start to whine fairly loudly and slight but noticable rolling lines appear in the video. I'd estimate that this occurs at ~60% APL and above. The video holds together well even when this is happening; it maybe looks like an analog over-the-air broadcast with the antenna not quite spot on.
It's actually my brother who's using this at the moment; he's an EE and will try to isolate the problem by tracking the sound first. However I think you all could probably shed some light, and maybe parts, on the situation. Any ideas?
Thanks!!
Ben
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Jan 08, 2008 2:53 am Post subject: |
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Power supply. Typical for the older sets, I never found a cure as I had enough spare PS to fix the couple that I resold. I have more SMPS that I'm giving away for the cost of shipping...
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Tue Jan 08, 2008 3:00 am Post subject: |
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| Curt Palme wrote: | | Power supply. Typical for the older sets, I never found a cure as I had enough spare PS to fix the couple that I resold. I have more SMPS that I'm giving away for the cost of shipping... |
Sold! A few questions for my education, though -
1) SMPS - you never see this term in relation to Marquees or Sonys (that I can recall) - why? - my best guess at the acronym is Switching Main Power Supply?
2) Is that the only power supply in the PJ? Or are there LVPS and HVPS like in the quees?
If you quote shipping to residential 20171 I'll pay right now.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Jan 08, 2008 3:10 am Post subject: |
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Switch Mode power supply.
Marquee = LVPS but it is indeed an SMPS. Same in all other projectors.
Email me at curtpalme@shaw.ca with your address. I'm about a week behind in sending out parts, but this week is catchup week..
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Sun Apr 20, 2008 1:49 pm Post subject: |
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I'm digging this up from the dead because my brother and I finally got around to working on the retro last weekend.
The replacement power supply we got is for a Vision 1500 - it looks identical save a few cap values, but the set is completely dead with that power supply in place, and I see from here: http://www.curtpalme.com/Barco400_Layout1.shtm that modules can often look identical but fail to work in another set. We did check the fuses to rule that out.
So back with the old power supply, we located the whining noise, and sure enough it's the main transformer, as indicated here: http://www.curtpalme.com/Barco400_Layout7.shtm
What we don't know is if the transformer could cause the video problem: The problem affects all three tubes roughly equally, so we think it's definitely a power supply issue. What happens when it breaks up is darker horizontal bands start flickering across the image seemingly at random. This condition can be easily induced by putting up a windows desktop with a white background and turning the brightness and contrast up a bit, and the video starts to break up before normal viewing brightness. We can start by pulling the transformer from the Vision power supply and putting it in the old power supply to attempt to fix the noise, but wanted opinions on if the video problem might lie elsewhere in the power supply.
Thanks,
Ben
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Sun Apr 20, 2008 2:06 pm Post subject: |
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Oh, one more thing of note:
In the Graphics 400 service manual, the SMPS section says to adjust trim pot 2, which is the master horizontal width trim pot, in order to get +24VDC at the pot. With the horizontal width set correctly so the image spanned the whole screen with small overscan, we got around 6VDC. Turning the pot so the voltage went up made the image smaller on screen, but only a max of about 7VDC or so with the image at probably half the normal width. How could this be so far off?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Sun Apr 20, 2008 2:30 pm Post subject: |
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I've never swapped transformers to see if that's the problem so PLEASE be my guinea pig and try it and post..
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Apr 20, 2008 2:49 pm Post subject: |
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You need to verify 28v coming into ic5. Pin 7 is 28+ and pin 4 is gnd. May not be easy to get at while installed so you may have to solder wires to these pins to connect meter to. If to difficult then observe schematic to find better location to solder wires.
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CRT_Ben
Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia
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| Posted: Sun Apr 20, 2008 3:20 pm Post subject: |
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| macgyver655 wrote: | | You need to verify 28v coming into ic5. Pin 7 is 28+ and pin 4 is gnd. May not be easy to get at while installed so you may have to solder wires to these pins to connect meter to. If to difficult then observe schematic to find better location to solder wires. |
Yeah, since it's pretty much impossible to get to the back of the board while installed, we've been soldering wires to various points as we go along. I'll try to get out to his house tonight and report back on what we find.
Thanks,
Ben
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