shmups.system11.org

Shmups Forum
 
* FAQ    * Search
 * Register  * Login 
It is currently Mon Jun 25, 2018 5:36 pm View unanswered posts
View active topics



Post new topic Reply to topic  [ 96 posts ]  Go to page Previous  1, 2, 3, 4
Author Message
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Wed Jun 13, 2018 5:13 am 



Joined: 03 Mar 2005
Posts: 304
Are you terminating the sync signal with a 75 ohm terminator at the monitor? If you are, then two things:

First, you're probably sinking a large amount of current from the Extron. It could be prone to running hotter, and something could even burn out inside of it.

Second, my 2050R2 does weird things based on what's happening on the sync line. I haven't done a thorough investigation, but I think that what is happening is that it detects whether the sync line is terminated with 75 ohms, and if it is, it then expects the sync pulses to be within a certain voltage peak-to-peak. If it's too high, the monitor will bias the entire picture.

For both points, you can fix the issue by putting a 560 ohm resistor in series with the sync line out of the Extron. Alternatively, if you're using an Extron for all of your consoles, you can probably get away with simply removing the 75 ohm terminator.

In my case, with an Extron 160xi outputting sync and a terminator on the monitor sync input, I saw that the picture was way too bright even with a 330 ohm resistor in series. A 560 ohm resistor, which brought the sync level down to a mere 0.5Vp-p, made it so that the monitor no longer biased the picture's brightness.


Top
 Offline Profile  
 
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Wed Jun 13, 2018 12:20 pm 



Joined: 18 Mar 2017
Posts: 16
Thanks for the response. When you ask if I am terminating the signal with a 75 ohm resistor, do you mean the terminator caps on the monitor loop outputs? I do have caps on those, but otherwise haven't added any resistors. Am I not supposed to have those on? I thought they were necessary to protect the monitor. Without the terminator caps on the output the display is much brighter, and the manual for a similar Ikegami says to use them when not connecting another monitor to the loop outputs.

Yeah, all of the consoles are connected to the Crosspoint.


Top
 Offline Profile  
 
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Thu Jun 14, 2018 5:02 am 



Joined: 03 Mar 2005
Posts: 304
NYI wrote:
Thanks for the response. When you ask if I am terminating the signal with a 75 ohm resistor, do you mean the terminator caps on the monitor loop outputs? I do have caps on those, but otherwise haven't added any resistors. Am I not supposed to have those on? I thought they were necessary to protect the monitor. Without the terminator caps on the output the display is much brighter, and the manual for a similar Ikegami says to use them when not connecting another monitor to the loop outputs.

Yeah, all of the consoles are connected to the Crosspoint.



You posted on reddit/CRT Gaming, too, right? I'm the guy who sent you those manuals. :)

The short answer is this: Keep all of the 75 ohm terminators on the monitor's R-G-B video inputs, but try taking the terminator off the sync input. If you're paranoid about your monitor's health, put a 560 ohm resistor in series with the sync line (get a cheap cable, open it up and splice it in) and leave the terminator on. Either way, even if it doesn't fix your color problem, it's guaranteed to be better for your Extron.

That Extron is outputting sync as a 5V peak-to-peak signal. That means that at the signal's lowest point, it's 0V, and at it's highest, it's 5V. The way these things are typically configured, the signal will be spending most of its time at 5V, and 75 ohm terminators are generally not meant to be used with such high voltages.

When an Extron applies 5V to a 75 ohm terminator, it bleeds out ~66mA of current, which is kind of a lot. Depending on how the Extron is built, that could be far too high for it and eventually cause damage. Also, with 5V on it, the terminator itself is dissipating ~333mW as heat; it's probably literally getting hot, and (again) depending on how it's built, it may even break.

Terminators are less about protection and more about preventing signal reflections. In theory, removing the terminator on the sync line should not actually cause the voltage on the monitor's input to rise. In practice, it probably will rise marginally, but it should still be within the unit's tolerance (IIRC, the manual says 6V max). Signal reflections aren't dangerous; they only cause performance problems. If you can remove the terminator from the sync input and not lose sync on the picture itself, then there is nothing to worry about. With the terminator removed, virtually no current will be bled from the Extron.

If you put a 560 ohm resistor in series with the cable and leave the terminator in, you get the best of all worlds. The Extron only bleeds ~7.8mA of current, the sync input on the monitor only has to tolerate a ~0.5V peak-to-peak signal (the 560 ohm resistor and the 75 ohm terminator form a voltage-divider), and finally, you're pretty much guaranteed not to experience any of the weird brightness-biasing of the kind that I saw.

Good luck!


Top
 Offline Profile  
 
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Sun Jun 17, 2018 3:08 am 



Joined: 18 Mar 2017
Posts: 16
SamIAm wrote:
NYI wrote:
Thanks for the response. When you ask if I am terminating the signal with a 75 ohm resistor, do you mean the terminator caps on the monitor loop outputs? I do have caps on those, but otherwise haven't added any resistors. Am I not supposed to have those on? I thought they were necessary to protect the monitor. Without the terminator caps on the output the display is much brighter, and the manual for a similar Ikegami says to use them when not connecting another monitor to the loop outputs.

Yeah, all of the consoles are connected to the Crosspoint.



You posted on reddit/CRT Gaming, too, right? I'm the guy who sent you those manuals. :)

The short answer is this: Keep all of the 75 ohm terminators on the monitor's R-G-B video inputs, but try taking the terminator off the sync input. If you're paranoid about your monitor's health, put a 560 ohm resistor in series with the sync line (get a cheap cable, open it up and splice it in) and leave the terminator on. Either way, even if it doesn't fix your color problem, it's guaranteed to be better for your Extron.

That Extron is outputting sync as a 5V peak-to-peak signal. That means that at the signal's lowest point, it's 0V, and at it's highest, it's 5V. The way these things are typically configured, the signal will be spending most of its time at 5V, and 75 ohm terminators are generally not meant to be used with such high voltages.

When an Extron applies 5V to a 75 ohm terminator, it bleeds out ~66mA of current, which is kind of a lot. Depending on how the Extron is built, that could be far too high for it and eventually cause damage. Also, with 5V on it, the terminator itself is dissipating ~333mW as heat; it's probably literally getting hot, and (again) depending on how it's built, it may even break.

Terminators are less about protection and more about preventing signal reflections. In theory, removing the terminator on the sync line should not actually cause the voltage on the monitor's input to rise. In practice, it probably will rise marginally, but it should still be within the unit's tolerance (IIRC, the manual says 6V max). Signal reflections aren't dangerous; they only cause performance problems. If you can remove the terminator from the sync input and not lose sync on the picture itself, then there is nothing to worry about. With the terminator removed, virtually no current will be bled from the Extron.

If you put a 560 ohm resistor in series with the cable and leave the terminator in, you get the best of all worlds. The Extron only bleeds ~7.8mA of current, the sync input on the monitor only has to tolerate a ~0.5V peak-to-peak signal (the 560 ohm resistor and the 75 ohm terminator form a voltage-divider), and finally, you're pretty much guaranteed not to experience any of the weird brightness-biasing of the kind that I saw.

Good luck!


That was me, and thanks again for that!

I did as you said and removed the terminator on the sync loop output. It didn't fix the purple text issue, but at least it'll be better for the life of the Extron as you said.

As an aside, the Xbox 360 through component looked fine in 720P/1080i, so this must be something about the way the Ikegami doesn't like the output coming from the RGB 192/is finnicky about sync. I tried a different VGA output, my laptop, and still got the purple text issue - using the VGA out from the Xbox 360, it wouldn't even sync.

Does anyone know whether having the VGA transcoded to component would fix this? Or would I run into the same problems?


Top
 Offline Profile  
 
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Sun Jun 24, 2018 4:13 am 



Joined: 18 Mar 2017
Posts: 16
Sorry to double post, but I also wanted to ask - if adding a 75 ohm terminator on the sync line loop output causes the Extron additional stress, what about using the Extron with a PVM, which is self-terminating?


Top
 Offline Profile  
 
 Post subject: Re: Wonky sync, AFC, and an Ikegami HTM-2050R2: Help wanted
PostPosted: Sun Jun 24, 2018 5:56 am 



Joined: 03 Mar 2005
Posts: 304
That's a good question. It's possible that a PVM puts anything and everything on 75 ohms, and it's possible that the circuitry detects higher voltages and terminates them differently. Anybody have a manual?

Extrons were expensive, and to be honest, I'd be surprised if they weren't built to be able to withstand 66mA flowing from the sync output. It's just that that might be stressful for it - I know that a lot of ICs have a max current rating of 20mA per pin. It also might cook your terminator - many resistors are only made to withstand up to 250mW.


Top
 Offline Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 96 posts ]  Go to page Previous  1, 2, 3, 4

All times are UTC


Who is online

Users browsing this forum: citrus3000psi, DarkAries, eric90000, Google [Bot], Nodoyuna, Ryoandr, Syntax and 18 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Space Pilot 3K template by Jakob Persson
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group