Skip to the last paragraph if you don't want to read the long story...

So my friend gave me his CRT HDTV, and I thought "Wow, I'll have the best of both worlds! A CRT TV for my retro gaming AND an HDTV." So right away I hook up my Retro Entertainment System clone, which played zapper games just fine on my 20 inch Sanyo CRT SDTV, but nothing happened! I couldn't shoot the ducks!

Later on I found out that this TV, and pretty much all CRT HDTVs, act like LCD HDTVs whereas they upscale 240p composite and S-Video to 480i. This is frustrating because not only do zapper games not work, but there's input lag too. Input lag on a CRT TV! I never would have known.

I have a Magnovox DVD recorder, fastastic piece of equipment btw, that can input composite and S-Video and convert them to 480i or 480p component video which results in some pretty darn good looking video quality for retro consoles on HDTVs. I try the RES through this route, and there's less input lag! The input lag returns though if I set my DVD recorder to 480i, but on 480p it's a lot less input lag. I can't explain why it does this, is it because it's 240p x2?

Anyway, my main reason for posting this topic is that I'm wondering... will zapper games work on my CRT HDTV if I used an NESRGB and plugged it into the 15.7khz 240p component input that my CRT HDTV supports? Will that eliminate input lag and the TV wouldn't do the bullshit post-processing of converting composite video to 480i like LCD HDTVs?

I should add that strangely my CRT HDTV seems to have less input lag through HDMI whenever I play my emulators on my Wii with a 480p Wii2HDMI adapter compared to using component video from my Wii. This seems to be the case with my 42 inch LCD HDTV as well, but on my 24 inch LCD-LED HDTV it's vice versa. I guess all HDTVs are different.

How does your TV draw its picture? That's the only thing that matters, as far as I know.

CRT HDTVs typically have one native HD resolution and run other ED or HD signals through an image processor/scaler. The ones that only accept one HD resolution are more likely to support native SD/ED, but it isn't common (supporting both 720p and 1080i would indicate an image processor/scaler in use). The Sony HD Trinitron sets will scale pretty much everything except very specific circumstances (I heard that my XBR910 will pass-through 525p but everything else is processed).

I would hook up a PlayStation 3 and test supported resolutions. If it only supports 720p or 1080i and not both, try an NES and see if light guns work! I'm curious to know myself what models might work.

It does indeed support both 720p and 1080i. It's a Samsung TX-S2782 just fyi. I have an Xbox 360 that I can use to test resolutions on it but I know the highest it can support is 1080i but it also does support 720p. It does not accept 480i on HDMI though, only analog inputs does it support 480i and lower.
 

Are you asking does it draw its picture like a typical CRT TV or more like an LCD TV? If so then I would say more so like an LCD TV, it just seems to act like an LCD HDTV with input lag and even seems to frame skip occasionally on 480i and even 480p (but not as often as 480i)
 

Light guns work by sensing where the CRT beam draws its frame. An LCD (or Plasma or DLP and other fixed pixel displays) show all the frame at once. That's why light guns like the Zapper don't work with them. It's not the lag so much as the nature of the TV.

So I'm not still not entirely understanding why Zapper games are not working on my CRT HDTV. All I know is that I've googled it and have seen youtube videos of people mentioning that zapper games don't work on any HDTV, including CRT HDTVs.

I should mention one thing I've noticed, the white flash you're supposed to see whenever you push the trigger, it doesn't show up on my CRT HDTV on real NES hardware. It does show up on my SDTVs and so the zapper works fine on those, plus there's 0 input lag on the CRT SDTVs.

Ugh, too much technical stuff. I just wish the zapper games worked because I only had space for either my Sanyo 20 inch SDTV or the 27 inch CRT HDTV my friend gave me. I chose the latter. The pros outweigh the cons on it, it looks stunning for Wii emulation on 480p HDMI. I guess at the very least, I can still play zapper games with my Wiimote on FCEU GX and it's not too bad actually. Also, I do see the white flash on the emulators but I know that it's only working because of the sensor bar, and because there's a crosshair that you move around with the Wiimote to aim at the ducks.

Edit: I will end this topic since my question actually had been answered by you Tulpa. The zapper games won't work on real NES hardware on my CRT HDTV, even on 240p component video. As you said, it has nothing to do with input lag. Thanks for the responses.

The Light Gun is locked to a 15KHz horizontal scan line frequency. SD CRTs only support a 15KHz horizontal scan line frequency. I believe that HD CRTs act like VGA CRTs in that they double 15KHz horizontal scan line frequencies to 31KHz. The lines get drawn twice as fast as your Zapper is expecting. You could get your zapper to work my modifying it to accept the higher frequency. I believe you have to replace the 390K resistor, but I am not sure whether the value has to be double (around 780K) or half (around 195K) or something else.

There's always some kind of framebuffer with HDMI, so the frequency isn't the only obstacle. Of all HDMI options, Hi-Def NES only buffers the minimum number of lines, but it would still throw off the timing for Zapper.

Unlike light pens and some other light guns (the more precise kind), the Zapper doesn't look at the timing/position of the scanline as it draws. The Zapper is looking for perfectly timed white/black transitions within full frames, so latency is the major issue here.​ Having a faster refresh rate alone probably wouldn't break it, but the image processing to adapt the signals would.  

Hi-Def NES starts sending the frame as the NES generates it, but the HDMI sink (receiving device) still needs to receive a full frame before it can display it, so best-case scenario: we get full frames, slightly delayed.

I think my CRT HDTV seems to be at 15KHz when it's showing a 240p component video signal, because I can just tell by looking at it that there's like more flicker or something on the TV when I have a 240p component signal sent to it, compared to any other resolution on the TV. Idk, I'm sure I'm wrong and that no matter what resolution, it's probably displaying 31KHz as you said. There's only one way to be sure, and that would be to use an NESRGB on my CRT HDTV and try out Duck Hunt. But I'm starting to be fairly certain that it most likely won't work.

I still find it odd that it'll accept and display 240p through its component input but not when plugging in composite or S-Video, I wonder why Samsung designed the TV that way.