Main > Monitor/Video Forum
HDMI to Old CRT
abstract3000:
Well, My friend told me had an Idea he wanted to try and I didn't hear back for a week it appears he ordered one of the Video amplifiers from Ultimarc as you suggested Zebidee, and in Positive news the Picture is now on the Screen (but appears to be inverted/ black/grey Scale with White Text) We are not understanding at what point the Video could have become inverted, but my friend wanted to give a shot at building an inverter to see if that fully corrects the issue. So waiting for those results.
Had I known this Sanyo Jungle was such a pain in the Ass I think I would have just spent more time trying to find a 27" CRT on FB marketplace to buy that either had the RGB inputs already or was something like Sony and well known to be capable of modding.
The theory we have with this TV is that the Jungle RGB Inputs are Digital therefore as speculated amongst the community is non moldable, but I believe we are bypassing that by raising the Analog Signal to the Same Voltage as Digital and fooling the chip to take it so to speak, but how good it will turn out at this point is anyone's guess :/
Zebidee:
More options for you:
"Neckboard" mod
Hacking directly into the jungle's RGB output to the neckboard. You don't necessarily have to do it physically at the neckboard either, you can probably do it right on the main chassis, before (or even at) the neckboard connector.
I've never actually done this myself. I know it is possible though. The main trick is to figure out the voltage levels.
The schematic I have shows RGB out on pins 19,20,21. It shows expected voltage levels for those pins, at 2.3 2.4 2.5 respectively. About 2.5v then. The block diagram (click on the thumbnail above) show RGB Vcc at 9v, so seems it uses that to give the RGB outputs a fair boost to ~2.5v.
That ultimarc amp should boost the RGB voltage to approximately same level, so worth a go.
Still need to terminate each RGB input with 75R resistors, and after that a ceramic cap (100nF 104) and a 100R resistor in series.
Like this x3, hijacking the neckboard connector (should be 5 pins, RGB+GND+9v). Alternatively, tap into the base of the 100R resistor already there. If the RGB is too bright, try pots (low value, probably 100R or 200R range sufficient) in series before the 75R terminations.
RGB input------?POT?-------------------CAP 104------100R------neckboard connector
|
75R
|
GND
Input the sync via composite as usual.
Pot on blanking signal
With the existing mod, and if your mate hasn't already done this (not sure if he has?), put a 3-pin pot on the blanking with middle pin to ground, to make a voltage divider. Try the full pot range. Different voltages may trigger different result. That's my "Hail Mary" for the OSD approach. Otherwise I think try hacking the neckboard/jungle output.
Inverted picture
Regarding the "inverted" video, you can easily address that by flipping the yoke coil connector. If you mean upside-down, flip the vertical coil connector. If you mean mirrored, then flip the horizontal connector. Each coil has 2 pins, typically joined as a 4-pin yoke connector. You would need to cut that in the middle, between the pins, to separate the H and V coils. Flipping the coils won't help with correcting the colour though.
abstract3000:
Thanks for the Info Zebidee, My friend Advised from the get go that hacking directly into the Neck was an option but one he would prefer to leave alone. It appears I spoke too soon in reference to what we thought was an inverted signal.
He got the picture coming through and in Color none the less, apparently the issue was the decoupling Caps, that were never present before, removed those and the Signal passes right through. Though 2 Things are a a bit off (the colors look really good an vibrant) but The screen resolution looks the same as it does on my PC monitor, so 640x480 is not what the TV is liking, so Going to have to find a way to Change the resolution it sends over.
The second thing is what we believe to be the Vertical Sync, there is some waviness of sorts around the screen, but I see in VMMaker adjustments can be made, I did play with it a bit when i was over there today and i saw it did change it, so will have to play with it a bit more.
Zebidee:
--- Quote from: abstract3000 on November 10, 2023, 10:15:18 pm ---Thanks for the Info Zebidee, My friend Advised from the get go that hacking directly into the Neck was an option but one he would prefer to leave alone. It appears I spoke too soon in reference to what we thought was an inverted signal. He got the picture coming through and in Color none the less, ...
--- End quote ---
Good news then! I was hopeful that you could do the input via OSD because you said you got a picture briefly, which means it must work somehow.
--- Quote ---... apparently the issue was the decoupling Caps, that were never present before, removed those and the Signal passes right through.
--- End quote ---
Try different values for the decoupling caps, perhaps one or two orders of magnitude lower or higher. The theory is that different capacitor/resistor combos resist different frequencies. High-pass or low-pass filters. I don't really want to go into theory I barely understand myself, but this is possibly what is blocking the signal.
Capacitors in parallel add total capacitance, so when testing it is easier to start small and go big. You just solder the higher capacitor onto the legs of the earlier one. If you used 104 (100nF) caps before, remove them and start with some 102 (1nF) or 103 (10nF) first. Then try some 105 (1uF) caps, even 10uF if you dare. Because 1.011uF is about the same as 1uF, you don't have to remove the smaller caps for this kind of testing.
--- Quote ---Though 2 Things are a a bit off (the colors look really good an vibrant) but The screen resolution looks the same as it does on my PC monitor, so 640x480 is not what the TV is liking, so Going to have to find a way to Change the resolution it sends over.
--- End quote ---
Not sure I understand what you mean there. Pics? Even with CRT_emulator, there remains a "native" 640x480 that is a VGA resolution hardwired in by Windows (thus "native"). Go into Arcade_OSD and change your desktop to the "custom" 640x480 interlaced res. Or something else :)
I'm mostly using 720x480i@60hz on my TVs desktops now - it is essentially NTSC standard. A tiny bit of letterboxing, but despite that the pic looks a lot crisper (an extra 80 pixels on each line) and seems easier to fit most of the desktop on screen, with little overscan. TV seems designed for it! Also saves me that native/custom confusion. I just add it to my user_modes list.
--- Quote ---The second thing is what we believe to be the Vertical Sync, there is some waviness of sorts around the screen, but I see in VMMaker adjustments can be made, I did play with it a bit when i was over there today and i saw it did change it, so will have to play with it a bit more.
--- End quote ---
There are all kinds of possible reasons for this. You sorted out that resistor on the sync input yeah? Maybe your mate could hook up the scope again and have a look, it looked wrong before (more like static). You need to zoom in to like 200us or less to really see it properly, because an entire line of sync is only ~64us long.
abstract3000:
--- Quote ---Try different values for the decoupling caps, perhaps one or two orders of magnitude lower or higher. The theory is that different capacitor/resistor combos resist different frequencies. High-pass or low-pass filters. I don't really want to go into theory I barely understand myself, but this is possibly what is blocking the signal.
--- End quote ---
I discussed this with My friend he stated he did tried a range with the caps and got nothing, hence removing them he realized it most likely wasn't going to go with them.
--- Quote ---Not sure I understand what you mean there. Pics? Even with CRT_emulator, there remains a "native" 640x480 that is a VGA resolution hardwired in by Windows (thus "native"). Go into Arcade_OSD and change your desktop to the "custom" 640x480 interlaced res. Or something else
--- End quote ---
I have gotten into the Arcade_OSD Swapped the Resolutions then put into the Emulation mode with multiple resolutions to no avail, I even tried changing the resolutions from the desktop while it was being emulated to the CRT with no Change.
See the Pic below, it's almost as if the Screen Area it's filling is larger than the actual "Viewing" area
I know this most likely has nothing to do with it, as they are separate but the LCD Monitor I'm using shows the Same damn thing when I put into Emulation mode
So the other issue I can't capture in a video or a picture is the "Flashing" maybe what I'm seeing is a Refresh issue? It occurs around Windows Boxes, menus etc, and the text in the Windows Explorer is pretty garbled, but when you put a Picture or a Video up, you don't get this quick "flashing" (excuse me I'm sure this has a proper term, but i don't know a better way to describe it)
--- Quote ---There are all kinds of possible reasons for this. You sorted out that resistor on the sync input yeah? Maybe your mate could hook up the scope again and have a look, it looked wrong before (more like static). You need to zoom in to like 200us or less to really see it properly, because an entire line of sync is only ~64us long.
--- End quote ---
At this point I am on my own :( I have the TV back and he stated he did everything he could do with it. I appreciate all his efforts, but I know it was taking up space in his shop he needed back and he really went through a lot to get it finished.
He did however leave the micro pot on the board for me to fine tune the blanking signal in the event i want to use the Svideo Option instead, but in his belief he really thinks there is something to do with the Vertical Synch and hopefully the Software/Drivers I'm using Can adjust that. I think I wil try setting up MAME on the System now and loading a Game to see how it even looks for that matter, but was hoping I could do something to get the screen adjusted so you could see the entire Windows Menu Bar at the bottom