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Adverse effects of combining H and V sync?

 
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gjaky




Joined: 05 Jun 2010
Posts: 2790
Location: Budapest, Hungary


PostLink    Posted: Wed Oct 15, 2014 5:20 pm    Post subject: Adverse effects of combining H and V sync? Reply with quote

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I am planning to completely realign the living room, which means the projector would have to go up to the ceiling (at last). I am planning to save on cables and would combine the H/V sync cables, resulting in four upgoing cables instead of five, to my understandig that should not affect the picture quality at all. Am I right?
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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24305
Location: Langley, BC

TV/Projector: All of them!
PostLink    Posted: Wed Oct 15, 2014 6:40 pm    Post subject: Reply with quote
No, no problems at all!
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gjaky




Joined: 05 Jun 2010
Posts: 2790
Location: Budapest, Hungary


PostLink    Posted: Mon Nov 24, 2014 9:20 pm    Post subject: Reply with quote
So, the projector is up on the ceiling, H and V cables tied together, so only 4 wires going up, it's not problem free. It only works if both sync polarity is the same. Fortunately my main resolution is +/+ but that's about it. My 3D dongle gets its sync from th V sync signal, it is not happy happy with the tied sync signals, it does not drive the glasses well.
I could build an active summing circuit for the syncs in the 3D dongle along with a sync inverting circuit, but what for? I'd better to pull in the fifth cable for separate sync...
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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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CasetheCorvetteman




Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Tue Nov 25, 2014 12:45 am    Post subject: Reply with quote
Yes, both syncs must be the same...

Wouldve certainly been easier to pull in 5 cables, and whiles youre at it pull in an HDMI cable too.
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gjaky




Joined: 05 Jun 2010
Posts: 2790
Location: Budapest, Hungary


PostLink    Posted: Wed Nov 26, 2014 10:52 am    Post subject: Reply with quote
CasetheCorvetteman wrote:
Yes, both syncs must be the same...

Wouldve certainly been easier to pull in 5 cables, and whiles youre at it pull in an HDMI cable too.


So guess What did I? Laughing
I considered pulling in the fifth cable as a PITA because the cable I used was special and to match for the rest I would have to order more. While I looked up the google for circuit solutions I realized that all of them are far "over complicated" built off logic IC-s. I didn't have any of those desired ICs either. So I decided to build my own comp sync + invert circuit from what I have. It consist of three generic NPN transistors and a few resistors. It works.

comp_sync+invert.jpg
 Description:
Composite sync "processor" + H sync inverting switch
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comp_sync+invert.jpg

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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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CasetheCorvetteman




Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Thu Nov 27, 2014 8:48 am    Post subject: Reply with quote
Well done Wink

The LM1881 chip will probably work simular, its about $2 AUD for 5 of them last time i bought a bunch.
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Barco CineMAX, 120" OZ Theatre Majestic 16:9 screen, H/K AVR 7.1...

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umarsahb




Joined: 25 Mar 2015
Posts: 1
PostLink    Posted: Wed Mar 25, 2015 9:52 am    Post subject: Reply with quote
I am planning to completely realign the living room, which means the projector would have to go up to the ceiling (at last). I am planning to save on cables and would combine the H/V sync cables, resulting in four upgoing cables instead of five, to my understandig that should not affect the picture quality at all. Am I right?
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redfox001




Joined: 16 Mar 2009
Posts: 2251
Location: The Netherlands


PostLink    Posted: Wed Mar 25, 2015 11:01 am    Post subject: Reply with quote
He when I look at the schematic there is a 5 V on the top? Where did you get that from? PC?
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gjaky




Joined: 05 Jun 2010
Posts: 2790
Location: Budapest, Hungary


PostLink    Posted: Wed Mar 25, 2015 6:13 pm    Post subject: Reply with quote
redfox001 wrote:
He when I look at the schematic there is a 5 V on the top? Where did you get that from? PC?


Most (modern) videocards sends out 5V on Pin 9 on the d-sub connector, that was originally a dummy leg.
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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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