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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Thu Jul 30, 2020 4:19 pm 



Joined: 14 Jul 2020
Posts: 13
Quote:
Wow that is nuts. I wonder what a 37 would go for? You rarely see them for sale.


I paid $2400 shipped for mine back in 2016 off ebay (XM37 Plus).


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Thu Jul 30, 2020 4:38 pm 



Joined: 14 Jul 2020
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lalilulelo wrote:
So, I've done some work on the monitor, and there have been some interesting developments.

...

Any insight about any of the things I mentioned would be appreciated.


I wouldn't disconnect the ground and run the set, not an expert but I think that could cause damage. Do you have soldering ability? I would go over those solder connections that you zoom in on in the 2nd pic. That looks like it could be corrosion. The solder joint may be cracked or somewhat broken free. You could also solder the crimped ring connector (if I'm seeing that right, kind of hard to tell) on the end of the ground strap in the first pic. Mfgs crimp things for cost savings but soldering it would be best.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Jul 31, 2020 1:51 am 


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basketballer wrote:
Do you have soldering ability? I would go over those solder connections that you zoom in on in the 2nd pic. That looks like it could be corrosion. The solder joint may be cracked or somewhat broken free.


I could probably do that, but what would be the best way to do it? Could I just solder it as it is, or would I need to discharge parts of the monitor first? Also, if I wanted to repair the solder points, should I try to remove the solder that's there and replace it, or should I just melt it and add a bit more to it?

basketballer wrote:
You could also solder the crimped ring connector (if I'm seeing that right, kind of hard to tell) on the end of the ground strap in the first pic. Mfgs crimp things for cost savings but soldering it would be best.


Yeah, I was thinking about trying something like that actually. I was thinking maybe I should connect a multimeter to the cable and the power input connector to try to see how stable the connection is - and if it's not stable, do something to make it more solid, like soldering it like you said. I was also thinking it's possible the metal ring that the wire is connected to could be corroded, in which case it might need to be replaced.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Jul 31, 2020 10:29 am 



Joined: 14 Jul 2020
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lalilulelo wrote:
I could probably do that, but what would be the best way to do it? Could I just solder it as it is, or would I need to discharge parts of the monitor first? Also, if I wanted to repair the solder points, should I try to remove the solder that's there and replace it, or should I just melt it and add a bit more to it?

Yeah, I was thinking about trying something like that actually. I was thinking maybe I should connect a multimeter to the cable and the power input connector to try to see how stable the connection is - and if it's not stable, do something to make it more solid, like soldering it like you said. I was also thinking it's possible the metal ring that the wire is connected to could be corroded, in which case it might need to be replaced.


I could be wrong, but I don't think you need to discharge the monitor to work on that portion. I would wipe the area down and clean it up as best you can with rubbing alcohol. Then add some flux paste around the solder joint. That will help the solder flow onto the surfaces. I'd also use rosin core solder. You can probably just add a little bit and keep what's on there, on there. If you get too much solder on there (not really a problem unless it makes contact with something it shouldn't) you can remove it with a desoldering wick.

Someone could answer this for sure, but I'm always hesistant to use a multimeter on a complete circuit because the resistance test does push some voltage through the wires. Probably ok in this situation (the amount of power the multimeter sends through isn't much compared to what that circuit normally sees), but in general I like to disconnect the wire or whatever I'm checking so as to not harm the circuitry. In this case part of the problem might be where the ground strap connects to the board, so removing the wire to test it doesn't tell a whole lot.

If that ring has corrosion on it, you might be able to clean it up enough to get it working without replacing. The corrosion could be on the ring surface where it mounts to the board (I'm imagining here as its hard to see in the picture), or it could be where the wire is crimped to the ring. The latter is where I would add solder just to be sure since that wire seems to have some problem. If you can get the solder to stick (with lots of flux), you can rule out that spot and move onto the next (if that doesn't fix the issue).


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Jul 31, 2020 12:20 pm 


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basketballer wrote:
I could be wrong, but I don't think you need to discharge the monitor to work on that portion. I would wipe the area down and clean it up as best you can with rubbing alcohol. Then add some flux paste around the solder joint. That will help the solder flow onto the surfaces. I'd also use rosin core solder. You can probably just add a little bit and keep what's on there, on there. If you get too much solder on there (not really a problem unless it makes contact with something it shouldn't) you can remove it with a desoldering wick.


I already tried it, in my own way. I had already cleaned it with alcohol previously - I think? I don't have flux, and I'm not sure if the solder I use is rosin core or not - but I'd guess probably so. Before I did anything else, I unplugged all of the cables that were connected to the power supply board, just to be careful. After that, what I did was I melted the solder that was already there and tried to remove a little bit of it, which didn't really work. I then added a bit more solder to each of the points. I noticed there was a bit of blackish/brownish residue afterwards - I wonder if this was rust that came out of the solder? I cleaned off the residue as best as I could. Upon reassembling the monitor and powering it on, it worked - so at least I'm pretty sure it didn't do any harm. It's too early to say if it fixed the issue though, because it often requires a few days of testing for the issue to appear. Realistically, based on all my experiences with the monitor so far, I'm not too optimistic about the chances of it working. If it does, then I'll be pleasantly surprised.

I did some game playing while I was testing it. I played through What's Shenmue, Sega Rally 2 and Virtual On for PowerVR on my PC, and then I played a decent amount of Escape From Monkey Island. I really love playing these games on this monitor - I just wish I could figure out this issue.

basketballer wrote:
Someone could answer this for sure, but I'm always hesistant to use a multimeter on a complete circuit because the resistance test does push some voltage through the wires. Probably ok in this situation (the amount of power the multimeter sends through isn't much compared to what that circuit normally sees), but in general I like to disconnect the wire or whatever I'm checking so as to not harm the circuitry. In this case part of the problem might be where the ground strap connects to the board, so removing the wire to test it doesn't tell a whole lot.


I wasn't talking about checking any circuits - the little cable is connected directly to the power plug in the back of the monitor. I just wanted to check the connection between the cable and the plug. As it turns out, I wasn't able to fully remove the screw - I'm not sure why. Anyway, I think I have a definitive answer about this cable now. What I did was I screwed in the cable fully, and then I connected one terminal of the multimeter to the power plug's ground pin, and connected the other terminal to the metal plate that the cable screws into - this plate appears to supply ground to both rear input boards. I found that the continuity was fine, and I tried jiggling the cable a lot and it had no measurable effect - the multimeter stayed at 0. So I'm now thinking that there's nothing wrong with that cable. If it had an effect before, then it's probably just an effect it had on some other issue rather than the cause of the issue itself. It could also have just been a coincidence. Either way, I don't think there's anything more I can do with that part of the monitor.

I hope what I did with the power input pins works, but we'll see. If it doesn't, then I have no idea what to do next.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Jul 31, 2020 6:47 pm 



Joined: 14 Jul 2020
Posts: 13
If the solder balled up on the end of the terminal, it may not have been well soldered to the board. What you want is a concave.. a picture is worth a thousand words. Check out this link https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems

Soldering older components, especially if there's some corrosion, can be difficult to get the solder to "take" that's where the flux comes in. Rosin core works ok, but adding flux will help the solder flow where you want it even more. If the problem comes back, maybe take a pic of the solder joint again and we can analyze it? Hope you get it figured out, these monitor are awesome


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Sat Aug 01, 2020 6:25 am 


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basketballer wrote:
If the solder balled up on the end of the terminal, it may not have been well soldered to the board.


It wasn't like that, as far as I could tell.

basketballer wrote:
Soldering older components, especially if there's some corrosion, can be difficult to get the solder to "take" that's where the flux comes in. Rosin core works ok, but adding flux will help the solder flow where you want it even more.


This didn't seem to be an issue. I melted the solder that was already there a bit before I added the new solder, so I was able to sort of mix the new and old solder together - and it seemed to adhere just fine.

basketballer wrote:
If the problem comes back, maybe take a pic of the solder joint again and we can analyze it? Hope you get it figured out, these monitor are awesome


I meant to take a picture after I was done soldering, but I forgot, and now it's all reassembled so I don't want to take it apart again. Like you suggested, I'll take some pictures if the issue comes back.

When and if I feel confident that the monitor is fully working, I want to make a video where I show the monitor and a bunch of games running on it. Technically I could do that now, but I'd rather wait until it's fully working. If I'm never able to get it fully working, I might still make some kind of video eventually. The strange thing about the monitor is that it can work extremely well for days, but inevitably the problem always comes back - and it kind of kills my enjoyment of it a little. But, the fact that it's so close to being fully working, plus the fact of how awesome it is in general, makes it so it's really hard for me to just give up on it.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Sat Aug 01, 2020 11:28 am 


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Small update: I did some more testing, and the problem came back - so apparently what I did had little to no effect. I have noticed that for some reason, since I've been fiddling with the power inputs, it seems like when the issue does occur, the onset of the worst part of it happens faster, and it also seems to go away faster. I'm not sure if that really means anything or not - the issue does seem to vary somewhat even if I do nothing. But it almost seems as if whatever's causing the issue is approaching a state where it's more stable as far as whether the issue occurs or not - as in, if that trend were to continue, eventually it would either have the issue all the time or not at all. I'm just thinking out loud.

I don't really know what to think at this point, but intuitively I feel like the ground input on the power supply board (the upper-most solder point in that picture I showed before) could be related to the issue - since the problem seems like a ground-related issue, and also because that point seemed to be the most difficult to work with of the solder points I tried to fix. This is just speculation.

I'll take pictures of the solder points like I said, but it may take me a few days to a week to do that. I've been opening up the monitor multiple times a week lately, and it's becoming rather tiring. I'll get around to it eventually, though.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Mon Aug 03, 2020 2:11 pm 


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Hello, My name is Logan Jones, I'm 19 years old, and I've just acquired an NEC XP-3790! I was able to get my hands on this beast from a FB Marketplace listing for free, and so far, its been working really well. It was originally one of five that were used at Turner Broadcasting in Atlanta, one on each floor. (They were also used for presentations at CNN.) In 2008, they were being thrown out, but a worker there got his hands on one and took it home. Years later, I saw his listing on FB Marketplace and snatched it up. I also have the original remote.

Image

The monitor seems to work fine for the most part. So far, in the two weeks that I've had it, Ive adjusted the focus so that the picture is sharper, adjusted the colors, toggled most the switches on the inputs to expect 75ohm, and boosted the brightness and contrast.

However, I have a few questions to ask and am in need of some support:

1) The image is not dark, but it is fairly dim, in case you can't tell from the photo. Despite turning the contrast and brightness all the way up, the image is still a bit faded. This has lead me to suspect that the monitor is due for a recap, since I heard that replacing the caps can restore the brightness and sharpness to a CRT monitor, but I will only do it if I have you guys to help me. Does anyone have a recap guide?
Image

2) The metal is dusty and has rust in some spots. I have already removed most of the dust on the outside, but what can I do about the rust? I thought about using something to remove the rust and then use some metallic paint to re-coat the parts. What do you guys think I should do?
Image

3) The sync momentarily drops out whenever white is flashed onscreen. This happens on both RGB inputs. What could be causing this, and how can I fix it?

4) The internal speakers are still functional, but are in the process of deteriorating. Does anyone know of some cheap and easy replacement speakers for this monitor?

5) What about replacement fans that are quieter?

6) I need a cart for this monitor. the monitor's base is huge and heavy (240lbs!), so I need a good cart to put it on. Do you guys have any ideas?

Is there anything else I should consider for the monitor? If so, let me know!

Thanks!


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Tue Aug 04, 2020 9:22 am 


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Logan Jones wrote:
1) The image is not dark, but it is fairly dim, in case you can't tell from the photo. Despite turning the contrast and brightness all the way up, the image is still a bit faded. This has lead me to suspect that the monitor is due for a recap, since I heard that replacing the caps can restore the brightness and sharpness to a CRT monitor, but I will only do it if I have you guys to help me. Does anyone have a recap guide?


Have you tried adjusting the screen adjustment on the flyback? That'll allow you to increase or decrease the overall screen brightness. I did this with my XV29 Plus, and it seemed to help at least a little. You should probably try not to turn it up too high, but from what I understand it won't cause any damage if you do - so the risk, if any, is pretty minimal. Just be sure not to shock yourself, but it seems like you already know that.

By the way, since you said you live in Atlanta, do you know of any places in Atlanta that'll repair this kind of monitor? I'm guessing not, I just thought I'd ask. It's interesting how a lot of these monitors seem to have a story behind them. Mine supposedly came from Wall Street.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Tue Aug 04, 2020 7:10 pm 


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Thanks for the suggestion. I thought about turning up the brightness via the "SCREEN" potentiometer on the flyback, but that still does not address the sync dropout issue.

BTW, I don't live in Atlanta, but in Jenkinsburg, a town 45 minutes southward. I'm willing to drive a ways, of course. However, when you mention a repair shop, does that mean you are suggesting I shouldn't bother with myself recapping this monitor? Because I have a friend who has years of experience soldering capacitors and components who can help me... Is recapping this monitor problematic or something?

If adjusting the screen voltage is optimal in this situation, do you know of anything I could use to mark the POT just in case when I do recap the monitor I can restore it to its normal voltage?

Thanks!


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Wed Aug 05, 2020 2:05 am 


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whiteout pen


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Wed Aug 05, 2020 3:07 am 


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Logan Jones wrote:
Thanks for the suggestion. I thought about turning up the brightness via the "SCREEN" potentiometer on the flyback, but that still does not address the sync dropout issue.


I wouldn’t worry too much about the sync dropout, unless it really bothers you. Does it happen a lot?

Logan Jones wrote:
BTW, I don't live in Atlanta, but in Jenkinsburg, a town 45 minutes southward. I'm willing to drive a ways, of course. However, when you mention a repair shop, does that mean you are suggesting I shouldn't bother with myself recapping this monitor? Because I have a friend who has years of experience soldering capacitors and components who can help me... Is recapping this monitor problematic or something?


I was asking because I’m looking for a repair shop/person. If you think you’re capable of doing the work yourself, then you should probably do it; I wasn’t suggesting you shouldn’t.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Wed Aug 05, 2020 1:52 pm 


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Quote:
I wouldn’t worry too much about the sync dropout, unless it really bothers you. Does it happen a lot?

I guess you could say it happens a lot... But only with bright white transitions. It happens whenever the PS1 boots up (white screen with SCEA logo then to Playstation logo is always a sync issue.) In Oddworld Abe's Exodus, bright fullscreen flashes from the bombs sometimes causes sync issues. The screen seems to also shift horizontally to the right a little whenever theirs a gradual dark-to-bright-to-dark transition. So yeah... the sync dropout does bother me a little...

Quote:
I was asking because I’m looking for a repair shop/person. If you think you’re capable of doing the work yourself, then you should probably do it; I wasn’t suggesting you shouldn’t.


I see. Yeah, my soldering skills are actually very rusty... but my experienced friend will be able to help me. And I'll even get a soldering iron Voultar recommended as a good start.

I mean, is there a cap guide online for this monitor? If not, perhaps I could take some steps to make my own for others to reference?

Thanks!


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Wed Aug 05, 2020 3:16 pm 


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Logan Jones wrote:
Quote:
I wouldn’t worry too much about the sync dropout, unless it really bothers you. Does it happen a lot?

I guess you could say it happens a lot... But only with bright white transitions. It happens whenever the PS1 boots up (white screen with SCEA logo then to Playstation logo is always a sync issue.) In Oddworld Abe's Exodus, bright fullscreen flashes from the bombs sometimes causes sync issues. The screen seems to also shift horizontally to the right a little whenever theirs a gradual dark-to-bright-to-dark transition. So yeah... the sync dropout does bother me a little...

Is it only on PS1? It could be a side effect of being forced to use a sync stripper. Another idea is you could acquire a second BNC patch cable and hook the HV sync outputs of the Extron I had you buy to the monitor instead of using c-sync. That might help


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Thu Aug 06, 2020 9:27 am 


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Your issue reminds me of this fix that people use on those Mayflash YPbPr to RGBHV transcoders:

https://playoffline.wordpress.com/cable/mayflash/

(set Google translate to English for the full article - here's the most relevant text, the link has some photos as well)

----------------------------------------
"The YPbPr to RGBHV VGA box from Mayflash is unfortunately a bit buggy. Game scenes in which abrupt light-dark jumps occur include a loss of the sync signal of approx. 2 seconds.

The problem is due to a poor dimensioning or assembly error on the board. The capacitor for the control of the sync unit on the IC LMH1251 pin # 11 is too high (about 44 times more than specified in the data sheet), so that there are 'incorrect impulses' when the image content changes suddenly.

Troubleshooting is relatively easy. Solder the 220nF SMD capacitor on the board and replace it with a 10nF ceramic capacitor."
----------------------------------------


Perhaps a loose or blown capacitor for the sync input of whichever port you've noticed the problem on the most...?

I'm not super PCB/replacement parts-savvy, but maybe this could be a starting point for diagnosis? Sure sounds like a similar problem! I'm sure someone else could weigh in
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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Thu Aug 06, 2020 11:28 am 



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What cable are you using between the Playstation and NEC, Logan? Doing a quick search online shows that the Playstation does not output clean c-sync and a sync stripper must be used as these NEC monitors only like c-sync. Have you tried another cable from a different mfg? Or a different console, perhaps one that outputs RGB and just csync? The earlier Super Nintendos (1chip-02 and earlier) output csync to their multi av connector.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Thu Aug 06, 2020 1:56 pm 


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basketballer wrote:
What cable are you using between the Playstation and NEC, Logan? Doing a quick search online shows that the Playstation does not output clean c-sync and a sync stripper must be used as these NEC monitors only like c-sync. Have you tried another cable from a different mfg? Or a different console, perhaps one that outputs RGB and just csync? The earlier Super Nintendos (1chip-02 and earlier) output csync to their multi av connector.

My PlayStation setup is a bit weird: From the the Ps1 to the NEC I have an AV breakout dongle connected to the ps1, and an official component cable connected to the dongle. The component cables then connect directly to the R,G, and B inputs on the NEC, and and composite video from the dongle goes to an Extron 192 so that the sync is stripped to C-sync and goes into the H/C input on the monitor and set to "High," since the the Extron is outputting TTL.

And perhaps I should try what Maxtherabbit suggested, and instead of using c-sync, use HV sync instead.

I also have a Dreamcast and Xbox 360 connected to the NEC over VGA. DC uses the Foo's VGA cable, and 360 is the official one. This actually started with the Dreamcast... The DC I recalled having greenish color flashes when there was bright white on the NEC, but not any sync dropouts per se...


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Aug 07, 2020 5:19 am 


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By the way, in case anyone was wondering (probably not), I'm investigating something new with the XV29 at the moment. I don't really want to discuss it right now, but I'll update back here if I find anything useful or possibly if I don't.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Aug 07, 2020 11:02 am 



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Logan Jones wrote:
basketballer wrote:
What cable are you using between the Playstation and NEC, Logan? Doing a quick search online shows that the Playstation does not output clean c-sync and a sync stripper must be used as these NEC monitors only like c-sync. Have you tried another cable from a different mfg? Or a different console, perhaps one that outputs RGB and just csync? The earlier Super Nintendos (1chip-02 and earlier) output csync to their multi av connector.

My PlayStation setup is a bit weird: From the the Ps1 to the NEC I have an AV breakout dongle connected to the ps1, and an official component cable connected to the dongle. The component cables then connect directly to the R,G, and B inputs on the NEC, and and composite video from the dongle goes to an Extron 192 so that the sync is stripped to C-sync and goes into the H/C input on the monitor and set to "High," since the the Extron is outputting TTL.

And perhaps I should try what Maxtherabbit suggested, and instead of using c-sync, use HV sync instead.

I also have a Dreamcast and Xbox 360 connected to the NEC over VGA. DC uses the Foo's VGA cable, and 360 is the official one. This actually started with the Dreamcast... The DC I recalled having greenish color flashes when there was bright white on the NEC, but not any sync dropouts per se...


I'm not sure that "HIGH" setting is for TTL level csync. I think its if the monitor is going to be using the thru (in and out to daisy chain monitors). The way I read the service manual, is that RGB1 can handle TTL level, but not RGB2 (which is the bnc inputs). Its a little unclear with the slash then the ..... but I think that's what they mean.

From the xm37 service manual
Image

edit here's the whole manual if you want to take a look at it https://mega.nz/file/knggEA6K#VW8idLFQoEkfgm4vhKq1EALG_SQFmerOtgN37zvIkJ4

kind of a shot in the dark, but does that Foo VGA cable for the Dreamcast put out a sync that the NEC can take? I could see if it was putting out TTL level sync on green and the monitor can only handle 0.3Vp-p, that could cause problems.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Aug 07, 2020 2:24 pm 


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You're not understanding. There are two switches for the BNC RGB input. One is for the colors (which should of course be set to 75) and the other one is for the sync.

All devices that output TTL sync expect high-z termination.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Aug 07, 2020 3:38 pm 



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maxtherabbit wrote:
You're not understanding. There are two switches for the BNC RGB input. One is for the colors (which should of course be set to 75) and the other one is for the sync.

All devices that output TTL sync expect high-z termination.


Those switches (I'm aware there's 2, but we're talking about the sync one) are to select whether its going to be daisy chained or not. Not to select TTL voltage level or 75 ohm. This monitor, according to the service manual screen shot I posted, cannot handle TTL level csync on RGB2 (it can on RGB1 tho).

Feeding this monitor TTL level csync on the 75 ohm circuit can damage it over time.

Image

my emphasis in red

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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Fri Aug 07, 2020 8:45 pm 


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I disagree with your interpretation of the service manual screenshot. It can take TTL sync on EITHER RGB input, but 75-ohm sync is an option only on RGB2 through use of the switch


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Sat Aug 08, 2020 11:29 am 



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maxtherabbit wrote:
I disagree with your interpretation of the service manual screenshot. It can take TTL sync on EITHER RGB input, but 75-ohm sync is an option only on RGB2 through use of the switch


What did they mean by "RGB2 only" then?

It can mean nothing other than RGB2 can only take 75 ohm.

Its not going to kill the monitor right away, I accidentally fed mine TTL csync for the last 3 years from my SNES. I just put on a 330 ohm resistor to bring it into spec. But over time, something like sync dropping out is exactly the kind of problems one would expect from significantly overdriving the sync circuitry.


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 Post subject: Re: NEC XM/XP 29/37 Pro/Xtra Thread
PostPosted: Sat Aug 08, 2020 3:34 pm 


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basketballer wrote:
It can mean nothing other than RGB2 can only take 75 ohm.

wrong

it can mean ONLY RGB2 can take 75ohm i.e. RGB1 can't take 75ohm, but RGB2 can


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