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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Mon Sep 13, 2021 11:16 pm 



Joined: 23 May 2013
Posts: 30
I may have spoken too soon. I made a quick and dirty vga female to vga male adapter that pulls the hsync line out into a resistor, then to an rca jack. Basically doing what maxtherabbit mentioned, but I didn't want to mess with the internal pins just yet.

In my previous test, I completely forgot that I had my misterfpga set to "forced_scandoubler=1" which makes it output 31kHz. But again, other than the scrolling screen, it looked fine.

Once I got my adapter put together, I changed the misterfpga back to normal 15kHz and turned on the composite sync. Hooked it all up and I got a stable picture, but it was extremely dark. I could only barely see the main mister menu. I thought maybe I missed a ground on my adapter or something, but even without the adapter (and back to a scrolling screen using the n64's composite) it was a still a dark picture with just the original vga cable. I've gone back and forth several times changing nothing but the "forced_scandoubler" setting and that's definitely what is affecting the brightness.

I'll test a bunch more tonight.

edit: It's also worth mentioning I use this misterfpga on a dual sync arcade monitor in 15kHz mode through a vga port, so I'm confident the darkness is not a quirk with the misterfpga itself.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 1:46 am 



Joined: 23 May 2013
Posts: 30
Progress! Maybe?

There's so much processing of the 31kHz sync, I thought maybe there's something that blocks or dissipates the vga rgb if that sync isn't present. So I upgraded my vga-vga adapter to add another female vga for feeding in the h and v sync. I hooked my dreamcast up to that one.
So I had the misterfpga feeding some 15kHz rgb through the vga port, and a 15kHz composite sync into the composite port, and the dreamcast feeding 31kHz h and vsync into the vga port.

And then I also had the monitor on the composite channel and TV/PC2 switched to pc mode.

Image
So I got proper brightness and a stable picture, but the colors get a little wonky and there's this diagonal line swiping across the screen like there's a problem with the sync. I'll have to stare at the schematics a bit longer to look to see if there's other logic things that happen when 31kHz sync is present.

Here are a couple pictures of my ridiculous setup right now :lol:
Image
Image


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 2:41 am 


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yatzr wrote:
So I had the misterfpga feeding some 15kHz rgb through the vga port, and a 15kHz composite sync into the composite port, and the dreamcast feeding 31kHz h and vsync into the vga port.

And then I also had the monitor on the composite channel and TV/PC2 switched to pc mode.


^^
God bless you child!! :mrgreen:

Looks like you are having some serious fun here. Also looks like you are very close to getting it to work. What is the reason for sending 31KHz h and vsync into the VGA port? Is the image of SMW above using just one or both of the syncs mentioned above-- and if just one, which one? Getting 31kHz H and V sync from a completely different system than what is feeding your RGB seems like it could cause all sorts of weirdness, especially when the signal you are trying to get is a 15kHz signal.

Keep at it and take a break if you get frustrated, then come back and attack it again when you are ready.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 3:10 am 



Joined: 23 May 2013
Posts: 30
Welp, now I do have to take a break. I tested out switching TV/PC3 and I think it fried something. I can't get any power on, though I hear a faint ticking sound like a switch is triggering. So uh, don't mess with that one :shock:


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 3:31 am 



Joined: 23 May 2013
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Josh128 wrote:
What is the reason for sending 31KHz h and vsync into the VGA port? Is the image of SMW above using just one or both of the syncs mentioned above-- and if just one, which one? Getting 31kHz H and V sync from a completely different system than what is feeding your RGB seems like it could cause all sorts of weirdness, especially when the signal you are trying to get is a 15kHz signal.

SMW should only be using the 15kHz that's going through the composite. The 31kHz was just an attempt to satisfy other circuitry that expects a 31kHz sync when using the vga rgb. I just took a guess that the missing 31kHz sync was causing my very dark image previously.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 12:31 pm 


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yatzr wrote:
Welp, now I do have to take a break. I tested out switching TV/PC3 and I think it fried something. I can't get any power on, though I hear a faint ticking sound like a switch is triggering. So uh, don't mess with that one :shock:


Well that sucks. How exactly did you go about switching TV/PC3? Just to see if I can help understand what may have fried. Maybe the jungle itself or something on that daughterboard?

On a more positive note, you have another pallet incoming--I just delivered it to the terminal yesterday afternoon, so you should have plenty of spare parts to swap in to narrow down the problem. I sent Eddie an email containing the BOL / Tracking Pro#.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 14, 2021 1:35 pm 



Joined: 23 May 2013
Posts: 30
Josh128 wrote:
Well that sucks. How exactly did you go about switching TV/PC3? Just to see if I can help understand what may have fried. Maybe the jungle itself or something on that daughterboard?

I pulled up one end of R026, similar to what I had done for TV/PC1 and TV/PC2. Soldered long wires to the now broken connection and hooked those up to a double throw switch. The strange thing is that I had gotten confused about switching it to 0V or 5V. It's already 5V in PC mode, and I hooked it up to switch with 5V. So I had the monitor on in pc mode, showing "Please connect 640x480" message with my 15kHz misterfpga being shown in the background. I flipped my switch and nothing happened, which seemed weird at first, but is obvious now because I switched it from 5V to 5V. Then I flipped the switch back, and that's when the tv just shut off. There wasn't any magic smoke or anything, and I don't think it made any sounds you wouldn't normally hear when turning it off.

I'll go through all the troubleshooting steps from the service manual later this week. I'm not too worried about it.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Wed Sep 15, 2021 10:40 pm 


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After some troubles, got my PC working on these sets. As I mentioned earlier, the image is extremely similar to the way a PC looks on the Weiya/Makvision M-3129.

yatzr wrote:
Once I got my adapter put together, I changed the misterfpga back to normal 15kHz and turned on the composite sync. Hooked it all up and I got a stable picture, but it was extremely dark. I could only barely see the main mister menu. I thought maybe I missed a ground on my adapter or something, but even without the adapter (and back to a scrolling screen using the n64's composite) it was a still a dark picture with just the original vga cable.


Turns out you must have -hsync and -vsync to make it work. If your system outputs +vsync and +hsync, you will get an extremely dark , barely visible image with ghosting and streaking. This may be what yatzr was seeing-- had he forced to negative sync, it may have worked. I have found that composite sync also works, but you must make sure its comprised of negative H and V sync or you get the same dark, unusable image. Also able to confirm the set syncs to resolutions at least up to 32KHz, tried a bunch of different ones via CRTemuDriver/ArcadeOSD.

Does anyone know if the default csync output of the SNES, Genesis, and other systems is positive or negative? This could be related to why he initially got the very dark image.



Below are photos of Windows and Groovymame (straight 2x, no scanlines) into the VGA port at 640x480.

https://i.imgur.com/Fbs8aIl.jpg
https://i.imgur.com/Scnv5E1.jpg
https://i.imgur.com/YT9VWrO.jpg
https://i.imgur.com/QD39Tyo.jpg
https://i.imgur.com/Ddtj1Af.jpg


Last edited by Josh128 on Thu Sep 16, 2021 10:11 pm, edited 1 time in total.

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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Thu Sep 16, 2021 3:47 am 


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As far as I know there aren't *any* consoles that output positive sync - or, at least 15kHz consoles (forget if Dreamcast and 360 are also negative). Definitely none that I've encountered.


https://www.instagram.com/p/CTQzNoOFQ8O/

^ Here is that Sampo / NetTV @ 720p totally FLEXING on the Hitachi. Not really, though, I am just kiddin' around... something the Hitachi appears to have over this one is that it seems almost 100% certain you'll successfully be able to do 15kHz and 31kHz via the same VGA input (you guys are already basically there). This monitor's VGA inputs are completely separate from the 15kHz inputs, which are on their own daughterboard. Maybe it would also be possible on mine via some clever fuckery, but I certainly have no idea!
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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Thu Sep 16, 2021 3:13 pm 



Joined: 23 May 2013
Posts: 30
kitty666cats wrote:
something the Hitachi appears to have over this one is that it seems almost 100% certain you'll successfully be able to do 15kHz and 31kHz via the same VGA input (you guys are already basically there).

I actually have a lot of doubts about it now. The main microcontroller I001 talks to I004 via I2C and sets a whole bunch of stuff like bright/contrast, rgb cutoff, sync detect and vertical centering. This only happens for the vga input. If you don't give I001 a 31kHz sync signal, it doesn't seem to tell I004 what you'd want it to and you end up with the super dark picture like I had. If you give it a dummy 31kHz sync (like I did with the dreamcast), then the rgb levels look about right, but there's other problems. I kinda think you would need to take the 15kHz sync that goes with the rgb you want and double it, then feed that to I001 on the 31kHz pin to make it happy.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Thu Sep 16, 2021 7:39 pm 


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Fuck. I only understand all this at a base level, but I really hope 15khz in rgb is an option. Does me hoping really hard help, lol?


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Thu Sep 16, 2021 9:02 pm 



Joined: 23 May 2013
Posts: 30
loopyeddie wrote:
Fuck. I only understand all this at a base level, but I really hope 15khz in rgb is an option. Does me hoping really hard help, lol?

Haha, I'm sure the osd trick will always be an option. I meant I have my doubts about sending 15khz into the vga and just tricking the monitor into showing it.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Thu Sep 16, 2021 10:10 pm 


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LoopyEddie wrote:

Yeah I already got the 15KHz RGB working via OSD mux so its proven to work going that route. Just didnt have it optimally configured resistance / impedance wise. The geometry, sync, and colors were perfect, just not as bright as it should have been.


It would have been cool as hell to get it working via the VGA port though. It looked like it was so close to working.

kitty666cats wrote:
^ Here is that Sampo / NetTV @ 720p totally FLEXING on the Hitachi. Not really, though, I am just kiddin' around...


Man that looks like a really small dot pitch tube, HD CRT style! These babies are exactly what you'd find in a Model 3 Blast City cab. The more I play with them the more Im impressed. MAME was looking very nice on them, and I wasnt even running scanlines on the 240p stuff. I also ran Mace:The Dark Age @640x480 and it looked very close to native 25KHz, just a tiny bit softer due to MAME upscaling it w/bilinear filter. Im confident I could tweak it to look as good as native, or run centered 512x384 @ 31KHz and just stretch the raster to make it perfect.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sat Sep 18, 2021 12:19 pm 


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Josh128 wrote:
Turns out you must have -hsync and -vsync to make it work.


That’s good news for OSSC owners, output sync polarity is always negative apparently. Linedoubled 240p with 100% scanlines should look great then and work out of the box with most HDMItoVGA adapters.
Although it would partially defeat the purpose to use a set like this with a linedoubler… :)
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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sat Sep 18, 2021 1:40 pm 


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Harrumph wrote:
Josh128 wrote:
Turns out you must have -hsync and -vsync to make it work.


That’s good news for OSSC owners, output sync polarity is always negative apparently. Linedoubled 240p with 100% scanlines should look great then and work out of the box with most HDMItoVGA adapters.
Although it would partially defeat the purpose to use a set like this with a linedoubler… :)


Disagree about the linedoubler defeating the purpose of this set-- it looks fantastic with linedoubler + scanlines from the GBS-C or 5X Pro. For those not wanting the hassle to RGB mod the set for 15KHz its a perfect alternative with the only lag being the external scalers lag, in which case a 2X Pro or 5X Pro is basically zero. GunCon 2 works! Only negative would be less brightness than true 15KHz RGB, but the set has enough brightness to easily compensate for that with the controls.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sat Sep 18, 2021 4:10 pm 



Joined: 15 Oct 2012
Posts: 17
I'm highly tempted by these sets.

I have a GBS-C AIO that could easily line-double with very little input lag, and I speculate that one of these would fit the bill if I wanted to output the native 240p/480i signal from the GScartSW:

https://www.ebay.com/itm/RGB-SCART-to-N ... 890.l49292

Would one of those work?


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sun Sep 19, 2021 12:03 am 


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twotone8 wrote:
I'm highly tempted by these sets.

I have a GBS-C AIO that could easily line-double with very little input lag, and I speculate that one of these would fit the bill if I wanted to output the native 240p/480i signal from the GScartSW:

https://www.ebay.com/itm/RGB-SCART-to-N ... 890.l49292

Would one of those work?


It absolutely would, situations like this are exactly what it was made for, heh. He makes a VGA (15kHz over VGA) one too (for use with CRT Emudriver/GroovyMAME & MiSTER etc etc). Antonio Villena makes one as well https://www.antoniovillena.es/store/product/vga-composite-s-video-adapter/
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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sun Sep 19, 2021 1:05 am 


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twotone8 wrote:
I'm highly tempted by these sets.

I have a GBS-C AIO that could easily line-double with very little input lag, and I speculate that one of these would fit the bill if I wanted to output the native 240p/480i signal from the GScartSW:

https://www.ebay.com/itm/RGB-SCART-to-N ... 890.l49292

Would one of those work?



As Kitty said, if they do what they are supposed to, they should work fine. S-Video looks damned fantastic on these sets, I hooked to Gamecube yesterday to check it out and while of course it was interlaced 15kHz, it was razor-sharp, looked very, very nice. Of course the optimum setup for GC would be to go 480p into the set with a component to VGA adapter or GBS-C (passthrough works fine). Dreamcast is exquisite via VGA.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sun Sep 19, 2021 10:27 am 


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GCVideo can do VGA 480p direct, or you can grab a Wii, do a 2 wire mod and flash it with a VGA CFW, they play GC games just fine.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Sun Sep 19, 2021 6:49 pm 


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Syntax wrote:
GCVideo can do VGA 480p direct, or you can grab a Wii, do a 2 wire mod and flash it with a VGA CFW, they play GC games just fine.


I’ve been curious about doing this, but I don’t use Wii too often & I have this thing:

https://blog.lhyeung.net/2009/08/11/vdigi-vd-w2-wii-vga-cable/

Image

It’s neat, particularly the dips on it for RGBS (for 15kHz). The in-line circuit for component to RGB transcoding is also quite nice, it’s got a LOT more going on than those crappy Wii/PS3 cables which serve the same function

(Hmm, the cable in the photo doesn’t show the dip configuration for RGBS on the hood… but mine does)
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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Mon Sep 20, 2021 11:56 pm 


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Ouch!! Got hit with an extra $270 charge for specifying the wrong weight on one of my shipments. Totally my fault, I feel like an idiot, but I put the weight of one monitor + pallet instead of 2 monitors + pallet by accident. FedEx fucking puts the screws to shippers who make mistakes on their weight calcs. Crazy thing is had I not made that mistake, the cost would have most likely only been $50-$70 more, and would have been paid by the buyer. I wont be making that mistake again. :shock:

Update on the reliability of these units after shipping-- since reflowing and adding fresh solder to the 4 or 5 potential problem locations on the mainboard I learned about early on, I havent had a single unit have an issue upon delivery. I have however, found MULTIPLE units with cracked joints on the very first problem transistor (Q72H) I identified. Fixed 'em right up and they were good to go! I dont ship units without pulling the back, inspecting the mainboard and reflowing all the potential problem areas.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 2:02 am 



Joined: 23 May 2013
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Josh128 wrote:
Ouch!! Got hit with an extra $270 charge for specifying the wrong weight on one of my shipments. Totally my fault, I feel like an idiot, but I put the weight of one monitor + pallet instead of 2 monitors + pallet by accident. FedEx fucking puts the screws to shippers who make mistakes on their weight calcs. Crazy thing is had I not made that mistake, the cost would have most likely only been $50-$70 more, and would have been paid by the buyer. I wont be making that mistake again. :shock:

Update on the reliability of these units after shipping-- since reflowing and adding fresh solder to the 4 or 5 potential problem locations on the mainboard I learned about early on, I havent had a single unit have an issue upon delivery. I have however, found MULTIPLE units with cracked joints on the very first problem transistor (Q72H) I identified. Fixed 'em right up and they were good to go! I dont ship units without pulling the back, inspecting the mainboard and reflowing all the potential problem areas.

Dang, that sucks. I hope you're making enough off of these to make it worth your while. You're really doing god's work here!
Don't know if Eddie mentioned it to you, but we started referring to these as "Joshtachis" :lol:

The one I fried by messing with TV/PC3 I have traced down to a bad bridge rectifier D901. Got a few replacements ordered. Fingers crossed there weren't more components affected further down the circuit.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 2:27 am 


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yatzr wrote:
Dang, that sucks. I hope you're making enough off of these to make it worth your while. You're really doing god's work here!
Don't know if Eddie mentioned it to you, but we started referring to these as "Joshtachis" :lol:

The one I fried by messing with TV/PC3 I have traced down to a bad bridge rectifier D901. Got a few replacements ordered. Fingers crossed there weren't more components affected further down the circuit.


Is that on the mainboard power supply section or on the jungle board? lol yeah Eddie texted me a picture of the rack hes building and told me that. Im building a little boneyard of units that all work but have some "issues". About 4 of them so far. One of the 4 is perfect other than a small "dot" of missing phosphor in the center of the tube-- doesnt look burnt, looks like it just "fell off" or something. Two of them have an identical strange squished pincushion screen problem that gets worse with higher brightness (and pincush controls dont work) and one seemingly works fine but doesnt "sync" to VGA-- it keeps telling you to connect a 640x480 PC even though you can see a darkened image of your feed on it. Im pretty confident I'll be able to nail down those probs and hopefully repair them, except for the one with the missing bit of phosphor. Its weird, Ive never seen that before, the spot is just totally black.

One day I'll have time to stop testing and shipping and actually work on these and play games on the few that I keep for myself. :)


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 2:47 am 



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Josh128 wrote:
Is that on the mainboard power supply section or on the jungle board?

Mainboard power. It's pretty close to the where the AC comes in, shortly after the fuse.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 7:20 am 


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Josh128 wrote:
One of the 4 is perfect other than a small "dot" of missing phosphor in the center of the tube-- doesnt look burnt, looks like it just "fell off" or something.


This can be caused by debris on the shadow mask.

I've never seen it in person, but according to a Sony maintenance manual you're supposed to hit the front of the tube with a rubber mallet in hopes that it can be dislodged. I don't know if I'd have the courage to do this myself! Doing a tube swap might be a better option, since you have other units with good tubes and defective chassis.


Last edited by matt on Wed Sep 22, 2021 8:20 am, edited 1 time in total.

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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 8:25 am 


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The dot is usually from running complete horizontal and vertical collapse set for too long (like 5 seconds).

All the energy from the gun focus' on a single spot which can be seen as a bright white dot and burns a hole in the phosphor.

I hear heating the phosphor with a hair dryer can blend crt burn in.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Tue Sep 21, 2021 12:40 pm 


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@ Syntax, yeah, at first I thought the same thing, focused dot in the center / burned phosphor, but it really looks like a small "flake" of the phosphor just fell off the tube face. Its not a perfectly round dot, more like a couple mm diameter irregular corn flake shaped piece is just missing. Its completely black, no luminance at all. To me, if it was caused by burn in, there should still be some luminance there albeit of a darker/different color than the rest. I guess that is unless the beam burned it till it fell off-- but if that was the case youd think the surrounding edges that didnt fall off would be discolored a bit from the heat and theyre not.

Theres nothing else wrong with the set, so I cant imagine anyone at the school board could have done something to make a focused beam at the center of the screen that could have caused that, but its not impossible. When I finally have more time to tinker and play with mods on these sets I'll post some pictures of this one. Its pretty interesting, Ive never seen that in a CRT before.

@Matt-- I thought about that and am really hoping thats what it is. I did move the set around and kind of lightly pick one side up a bit and drop it, hoping that if it was debris or trash it would shake loose, but that didnt work. The rubber mallet idea is interesting! I may have to try it before giving up hope, not too worried about the tube, because it has this issue. I dont want to break it , as it has a great picture otherwise and can be good for testing other parts, but Im not worried about trying a few good whacks. :mrgreen: It really does look to me that the phosphor just flaked off and is missing though.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Wed Sep 22, 2021 7:58 am 


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I wouldn't have thought of the mallet trick either! It's from the following Sony manual:

https://elektrotanya.com/sony_ctv-25r1_ ... nload.html

Spoiler: show
Image


Is the spot visible when the screen is off? If not, I'd imagine the phosphor itself is still OK and the shadow mask is the culprit.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Wed Sep 22, 2021 8:57 am 



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That trick takes advantage of the structure of the aperture grill mask where the wires can vibrate to some extent (like guitar strings) but I don't really think it will work on a shadow mask which is a single rigid piece.


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 Post subject: Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??
PostPosted: Wed Sep 22, 2021 9:14 am 


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Yeah, I figured as much but it's worth trying.


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