DIY VGA to component transcoder - AVS Forum
Forum Jump: 
Closed Thread
 
Thread Tools
post #1 of 1065 Old 11-24-2002, 08:48 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi,

Has anyone built the transcoder based on the schematic showed here? : http://63.218.43.67/keohihdtv/interf...ranscoder.html
Id like to try it but I can't find the EL2045 OPAMP anywhere. Ive tried to find a good substitute but I just don't know wich kind of OPAMP I need. Also is it compatible with 1080i without much modification? Ive tried to contact the designer but he does not respond.

Thanks for any help!
DPW666 is offline  
Sponsored Links
Advertisement
 
post #2 of 1065 Old 11-25-2002, 10:11 AM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
bumpity
DPW666 is offline  
post #3 of 1065 Old 11-25-2002, 01:54 PM
AVS Special Member
 
Ken Erickson's Avatar
 
Join Date: Feb 2001
Location: Willis, TX 77318
Posts: 1,106
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
The link you posted is broken.
Ken Erickson is offline  
post #4 of 1065 Old 11-25-2002, 02:32 PM
AVS Special Member
 
Jeff D's Avatar
 
Join Date: May 2000
Location: One step ahead of you
Posts: 8,273
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 14
I think you are talking about the one you are talking about, Jon Reehs made it?

I saw the plans and it didn't look like it would work for what I needed, so I went out and bought one. AA 9A60 is what I went for. The trick about transcoders is noise and timing...
Jeff D is offline  
post #5 of 1065 Old 11-25-2002, 06:23 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
oopss sorry here is the correct link : http://www.keohi.com/keohihdtv/inter...ranscoder.html

so you guys think it would be better to just buy one? I just don't want to pay more than 50$ for it...Im kinda really low on cash since I rebuilt my HT.
DPW666 is offline  
post #6 of 1065 Old 11-25-2002, 10:19 PM
AVS Special Member
 
Jeff D's Avatar
 
Join Date: May 2000
Location: One step ahead of you
Posts: 8,273
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 14
I'd say buy... Jon's design is simple, but it sounds like it worked for him. Can't cost more that $20 to try, right?
Jeff D is offline  
post #7 of 1065 Old 11-26-2002, 07:00 AM
AVS Special Member
 
Teeps's Avatar
 
Join Date: Aug 2001
Location: Torrance,Cal. 90503
Posts: 1,044
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 12
Never build what you can buy, that's my advice.

Unless your a really skilled electrician, you'll likely have to build the project at least two times. Specially if you are working from "just a schematic."

Just my 2cents worth.

Cheers, Tp

"No lawsuit ever fixed a moron."
Teeps is online now  
post #8 of 1065 Old 11-26-2002, 11:02 AM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
well I am an avid DIYer. Ive built things from audio power amps to computer scan converters. The only thing Id like is find a replacement for the EL2045 chip. I can't find it locally nor on the web. If anyone knows of a good replacement please let me know it.


Thanks a lot!
DPW666 is offline  
post #9 of 1065 Old 11-26-2002, 11:21 AM
Member
 
ajira99's Avatar
 
Join Date: Sep 2001
Posts: 141
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally posted by DPW666
well I am an avid DIYer. Ive built things from audio power amps to computer scan converters. The only thing Id like is find a replacement for the EL2045 chip. I can't find it locally nor on the web. If anyone knows of a good replacement please let me know it.


Thanks a lot!
You may want to try something like a Linear Technology LT1812. The EL2045 is just a 100MHz op amp with a high slew rate. The LT1812 is rated at 100MHZ and 750V/us.
ajira99 is offline  
post #10 of 1065 Old 11-26-2002, 11:27 AM
AVS Special Member
 
Jay Wilson's Avatar
 
Join Date: Apr 2001
Location: Orange,TX, USA
Posts: 2,857
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
How about the other way...from component to RGB?

Thanks a million...Good luck...Let us know... Whichever is appropriate this time! jmwj03 at hotmail dot com
Jay Wilson is offline  
post #11 of 1065 Old 11-26-2002, 12:13 PM
AVS Special Member
 
Jay Wilson's Avatar
 
Join Date: Apr 2001
Location: Orange,TX, USA
Posts: 2,857
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Thanks SDDI! Very cool! What would happen to sync in that example? Would it be on the green?

Thanks a million...Good luck...Let us know... Whichever is appropriate this time! jmwj03 at hotmail dot com
Jay Wilson is offline  
post #12 of 1065 Old 11-26-2002, 12:22 PM
AVS Special Member
 
Jay Wilson's Avatar
 
Join Date: Apr 2001
Location: Orange,TX, USA
Posts: 2,857
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I'd really like to see your results when you're done!

Thanks a million...Good luck...Let us know... Whichever is appropriate this time! jmwj03 at hotmail dot com
Jay Wilson is offline  
post #13 of 1065 Old 11-26-2002, 12:26 PM
AVS Special Member
 
Mooneyass's Avatar
 
Join Date: May 2001
Location: Calgary, Alberta, Canada
Posts: 1,328
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Me Too!

I hate Sony. I love BD. I hate Sony...

My Blog
Mooneyass is offline  
post #14 of 1065 Old 11-26-2002, 12:50 PM
Advanced Member
 
Mr.Pibb's Avatar
 
Join Date: Jun 2002
Location: Lewis Center, OH
Posts: 543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
So with that, are there any other schematics for vga -> component?

I'd be willing to try to build one of these, but I don't yet have an HDTV to try it out on. :-(

I'd even be willing to build them and sell them for cost of parts plus a little labor. It would be nice to know if it actually works, though.

Tim

Before you criticize someone you should walk a mile in their shoes.
That way, when you criticize them, you are a mile away and you have their shoes!

Setting up Powerstrip with a Sony A10 LCD RPTV
Mr.Pibb is offline  
post #15 of 1065 Old 11-26-2002, 07:43 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Thanks alot guys! I finally found the chip and will build it asap. I will post results when Im done!
DPW666 is offline  
post #16 of 1065 Old 11-27-2002, 05:17 AM
Advanced Member
 
Mr.Pibb's Avatar
 
Join Date: Jun 2002
Location: Lewis Center, OH
Posts: 543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally posted by DPW666
Thanks alot guys! I finally found the chip and will build it asap. I will post results when Im done!
Great! Keep us informed!

Also, if you don't mind, let us know where you found the components and the costs. I found the linear technology chip at digikey for almost $3 each(unless you order 100 or more). I've noticed digikey can be expensive if you aren't ordering high volumes.

One more thing, does your hdtv accept 720p inputs? The TV I'm considering purchasing does and I am curious on the performance of the diy transcoder with that signal.

Good luck!
Tim

Before you criticize someone you should walk a mile in their shoes.
That way, when you criticize them, you are a mile away and you have their shoes!

Setting up Powerstrip with a Sony A10 LCD RPTV
Mr.Pibb is offline  
post #17 of 1065 Old 11-27-2002, 05:38 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Ok, I ordered some samples of this chip from Texas instruments : http://www-s.ti.com/sc/psheets/sbos044/sbos044.pdf
Do yous guys think it is enough for this application? I chose it because it is a quad opamp so it will simplify the circuit. It says it is good for high resolution video. When I'll receive the samples I'll built it and post results.
DPW666 is offline  
post #18 of 1065 Old 11-27-2002, 06:27 PM
Advanced Member
 
Mr.Pibb's Avatar
 
Join Date: Jun 2002
Location: Lewis Center, OH
Posts: 543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I think it's worth a shot! Are they sending you the samples for free?

Tim

Before you criticize someone you should walk a mile in their shoes.
That way, when you criticize them, you are a mile away and you have their shoes!

Setting up Powerstrip with a Sony A10 LCD RPTV
Mr.Pibb is offline  
post #19 of 1065 Old 11-27-2002, 06:48 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
yes they are...but I actually found a better one the LMH6715 from National. It is specified for HDTV applications. Very wide bandwidth and high slew rate. Perfect for what we want to do. It is a dual opamp so only 2 chips are needed. Here is the datasheet: http://www.national.com/ds/LM/LMH6715.pdf

I also requested samples. And yes, they are free! :D Even shipping. But please lets not abuse from them if the circuit works ;)
DPW666 is offline  
post #20 of 1065 Old 11-27-2002, 07:50 PM
Advanced Member
 
JeffDM's Avatar
 
Join Date: Jun 2001
Location: Michigan, USA
Posts: 722
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
The transcoder is a fascinating design, quite simple in concept _and_ design.

I agree, to me, it appears that any good high bandwidth, high slew rate opamp should do, if the output resistance is good. Chips that can drive long 75 ohm cables are quite common, but something specifically designed for HDTV should do quite nicely, such as the chip mentioned above.

I am interested in seeing the results, although I really don't need one.
JeffDM is offline  
post #21 of 1065 Old 11-30-2002, 08:48 PM
AVS Special Member
 
Jeff D's Avatar
 
Join Date: May 2000
Location: One step ahead of you
Posts: 8,273
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 14
Wow, I had posted a question like this on HTF DIY area and nothing like the results here.

I went with the AA transocder because it wasn't that expensive. I would like to make on myself for fun. Count me in on interested in seeing the final design!
Jeff D is offline  
post #22 of 1065 Old 12-02-2002, 02:46 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I am still waiting for the samples, but I tried the circuit with some generic opamps to test it and 480p works!! Others resoltutions didn't work. I suspect the the low bandwidth the opamps have and the bad wiring I used since I did it as a test. But it looks promising! When the chips come I'll desing a PCB with proper layout for this kind of application and see what kind of resolutions I can get.
DPW666 is offline  
post #23 of 1065 Old 12-02-2002, 02:49 PM
Advanced Member
 
Mr.Pibb's Avatar
 
Join Date: Jun 2002
Location: Lewis Center, OH
Posts: 543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
That's great news! I like to build stuff like that anyway so it looks like I have a project once I purchase the HDTV!

Keep the good news coming!

Tim

Before you criticize someone you should walk a mile in their shoes.
That way, when you criticize them, you are a mile away and you have their shoes!

Setting up Powerstrip with a Sony A10 LCD RPTV
Mr.Pibb is offline  
post #24 of 1065 Old 12-02-2002, 04:17 PM
Advanced Member
 
jon_rhees's Avatar
 
Join Date: May 1999
Location: Riverton, UT, USA
Posts: 669
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally posted by DPW666
I am still waiting for the samples, but I tried the circuit with some generic opamps to test it and 480p works!! Others resoltutions didn't work. I suspect the the low bandwidth the opamps have and the bad wiring I used since I did it as a test. But it looks promising! When the chips come I'll desing a PCB with proper layout for this kind of application and see what kind of resolutions I can get.
DPW666,

When I designed this circuit (the one you're using from the keohi site), I was only targetting progressive resolutions (480p, 720p, etc.). Interlaced res's like 1080i require tri-level sync, and depending on the TV, this circuit may need additional sync generation circuitry to work with a particular model. Also, you need to keep in mind that the color matrix changes slightly for 1080i. So, colors will be a bit off.

-Jon
jon_rhees is offline  
post #25 of 1065 Old 12-02-2002, 05:52 PM
Advanced Member
 
Mr.Pibb's Avatar
 
Join Date: Jun 2002
Location: Lewis Center, OH
Posts: 543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hey Jon,

So it should work fine for 720p? That's good news! Did you do any more work with it or did you move on to other stuff?

Thanks!
Tim

Before you criticize someone you should walk a mile in their shoes.
That way, when you criticize them, you are a mile away and you have their shoes!

Setting up Powerstrip with a Sony A10 LCD RPTV
Mr.Pibb is offline  
post #26 of 1065 Old 12-03-2002, 07:52 AM
Advanced Member
 
jon_rhees's Avatar
 
Join Date: May 1999
Location: Riverton, UT, USA
Posts: 669
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
No, I didn't do any more work on it. I still use the original design today in my system. Back when I designed this (before AA960 or RCA or Key Digital versions even existed) a few people told me that I should finish up a design and market it. I told them I thought there wasn't enough interest and that all TV's would have RGB inputs on them in the future anyway. HaHa, I guess I was wrong!

-Jon
jon_rhees is offline  
post #27 of 1065 Old 12-04-2002, 09:19 AM
Senior Member
 
kealii's Avatar
 
Join Date: Oct 1999
Location: Reston, VA
Posts: 485
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi jon,

I remember our discussions about that. :)

How similar are the existing transcoder designs to yours? Have you "cracked open" any of them?

r,
Errol

Keohi HDTV
Your Friendly HDTV Tips Site
kealii is offline  
post #28 of 1065 Old 12-17-2002, 11:49 AM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi,

I finally received the samples and finished the transcoder. As the designer said, only progressive resolutions works, but hey, thats better than nothing. I currently am running my tv in 800x600 and the image is beautifull. So it think that for the 10$ it costed me to build it is a good investment. Maybe one day someone with good knowledge will add a circuit for interlaced resolutions.
DPW666 is offline  
post #29 of 1065 Old 12-17-2002, 12:32 PM
Member
 
Harry Azol's Avatar
 
Join Date: Dec 2002
Posts: 57
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Any chance that someone could post a detailed guide of how to build this? ie: the power supply, board layout, changes from Jon's design,etc

I'm pretty familiar with making digital circuits, but this analog stuff is out of my league.
Harry Azol is offline  
post #30 of 1065 Old 12-17-2002, 02:05 PM - Thread Starter
Member
 
DPW666's Avatar
 
Join Date: Nov 2002
Posts: 40
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I did not change anything from the original circuit except for the chips. Board layout will differ with the op-amps used. Just keep everything as close as possible to keep short signal path. If you can, put everything in a sheilded box for interference. Use good quality connectors. Also as Jonh said try to use SMD components also to keep signal path as short as possible. There are only two trim pots so fine tuning is not very difficult.
DPW666 is offline  
Closed Thread Home Theater Computers

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off