Hitachi 27" 27MM20B Dual-Scan CRT TV??

[matt]

The weird thing about these TVs is that they will sync just fine with composite sync. However, without a signal on the Vsync pin it gives the "connect a PC" error message (even though you can still see a stable image in the background). It works fine with Csync+Vsync, though.

[8bitForLife]

So if i wanted to keep my gscartsw and try to keep the unplugging to a minimum. does scart give the same tesolutions vga does? sorry for newbie questions only ever messed with scart.

[strayan]

Ill also be using a dreamcast and I have the scart cable from retro access for it but is there anything else ill need?

I'd recommend against using the Retro Access SCART cable. This TV doesn't like composite sync - you'd be better off using a VGA box or cable. A cheap Dreamcast VGA cable would probably work fine.

If he connects a RA Dreamcast SCART cable to a GBS-C AIO then composite Sync is irrelevant since the GBS-C outputs seperate H & V sync.

[matt]

So if i wanted to keep my gscartsw and try to keep the unplugging to a minimum. does scart give the same tesolutions vga does? sorry for newbie questions only ever messed with scart.

Usually not. It's supposed to be used for 15khz RGB with composite video for sync, which is quite different from VGA (31khz RGB with TTL level H/V sync). These Hitachis only accept standard VGA in RGB mode, so anything with a SCART connector will require some sort of conversion.

But, what the RA cable does is to run the Dreamcast's H and V sync through a combiner circuit to provide composite sync. This means that it can pass a 31khz signal, but with composite sync instead. This is not a standard configuration, but it's useful if you have something that's compatible with it.

In your case, you should be able to run it through your GSCART/GBS-C combo, which would also let you run 240p-only games like Bangai-O and Gunbird 2 if needed.

[yatzr]

I just recently ran into a weird issue with mine and I'm curious if anybody else has had this happen.

I was testing an nes with composite video on it and everything was fine for 10 minutes, then the video went black. The OSD can still come up fine. I cycled through the inputs and normally I'd get a grey screen on s-video if nothing is connected, but it was also black. Then on the regular tv channel, I normally see "snow" static, but it was also black (can still hear the static though). I panicked and tested my pc input which I normally use exclusively, and everything was fine there. So it appears I've just lost normal video output on all the 15khz channels. The OSD still works fine on all of them.

I did a whole bunch of power cycling, reconnecting things, etc. I couldn't get the video to come back.

[8bitForLife]

anyone selling 1

[Josh128]

I just recently ran into a weird issue with mine and I'm curious if anybody else has had this happen.

I was testing an nes with composite video on it and everything was fine for 10 minutes, then the video went black. The OSD can still come up fine. I cycled through the inputs and normally I'd get a grey screen on s-video if nothing is connected, but it was also black. Then on the regular tv channel, I normally see "snow" static, but it was also black (can still hear the static though). I panicked and tested my pc input which I normally use exclusively, and everything was fine there. So it appears I've just lost normal video output on all the 15khz channels. The OSD still works fine on all of them.

I did a whole bunch of power cycling, reconnecting things, etc. I couldn't get the video to come back.

I have 1 unit where 15kHz outright failed, displays a weird rainbow colored thin column from top to bottom, no legible OSD. 31KHz works fine though. I had replaced a transistor (dont remember which, somewhere in the 15KHz circuit path) and it fixed the 15kHz! Then, it went out again, exactly the same way.

Did you try swapping the jungle/video daughterboard?

[thchardcore]

I just have to chime in once more and mention what a nice guy Josh is. He went out of his way for a total stranger and I feel I owe him more than just the small amount he asked for these things.

Thank you again Josh. You are cut from a different cloth.

[Josh128]

You're welcome! Amazing the difference in UPS shipping outright vs Ebay UPS shipping eh? Literally double.

[Josh128]

So my awesome friend @overlordmanny has done it again. Designed and printed a speaker cover replacement for the Hitachi sets. The stock covers are extremely brittle and some of the units I shipped had cracked or missing covers upon reaching destination. I asked him not to worry about latching tabs, these fit right into place and are meant to be secured with a few tacks of glue. They would need to be color matched painted to look original, any matte smoke gray color would probably work fine.

Although he is not asking for any money for these, I told him the least I can do is get him a few bucks for his trouble. It takes 3 hours to print one of these, so if anyone is interested, it'll be $10 per side + shipping.

[thchardcore]

You are my hero...at least this month.

[matt]

Just a gratuitous Mushi 2 TATE VGA screenshot...

[Josh128]

Both your units still working? My Ultravision Digital unit recently started making a arcing/snapping sound periodically, in which the screen blinks. I havent opened it up, but Im hoping its not the flyback. I have a couple spare units to work with, hopefully I can resolve the issue.

[matt]

Yes, they both work fine. After fixing the blown HOT I've had no further problems. Still need to check more of the caps, and I have some ideas for a 15khz RGB mod, but I keep getting distracted with Xbox & Dreamcast games and haven't gotten around to it.

[kitty666cats]

Yes, they both work fine. After fixing the blown HOT I've had no further problems. Still need to check more of the caps, and I have some ideas for a 15khz RGB mod, but I keep getting distracted with Xbox & Dreamcast games and haven't gotten around to it.

Yeah, I am hoping to see someone finish working out the kinks for 15kHz RGB on these things! I don’t have one or need one, but I have enjoyed watching this whole Hitachi-saga play out.

[matt]

The problem is that they work so well with a line doubler that there's not much pressure to figure out a 15khz option.

[8bitForLife]

does anyone have one of these for sale?

[Josh128]

The problem is that they work so well with a line doubler that there's not much pressure to figure out a 15khz option.

This is precisely why I halted my work on the 15KHz RGB option. I got it working back on page 5, but it needed some more TLC for the brightness. I was still super busy packing and shipping and had just discovered how cool and easy it is to polish scratches from CRT glass, and my initial results looked so identical to a line doubler @ 31KHz I dropped the project.

Technically speaking, the only advantage for the 15K option over 31K is that the 15K should be brighter. The S-Video to these sets is among the best Ive seen, so thats another knock against spending more time on the 15K RGB option. S-video does seem to need some added attenuation on the luma line though as bright flashes cause a brief sync loss. That would be a worthy project, IMO.

Now IF someone could get a mod that would allow 15K RGB into the VGA port, as yatzr almost achieved, that would be cool. Im not sure if that will happen though.

[matt]

I think 15khz through the VGA circuit may be the best option. You could do an OSD mux mod through the TV side, but those Toshiba jungle chips aren't ideal for it. They have non standard input voltages and the brightness isn't adjustable from the user menu.

My impression, based on looking at the schematic and reading Yatrz's posts, is that you could run sync through the jungle chip while running RGB through the VGA amp.

[KPackratt2k]

From my experience and research, the jungle chip used in these TVs (Toshiba TA1268N) expect a 1Vpp RGB signal. If you just use a 0.7Vpp input, the brightness would be too dark. If you're going back to working on getting 15KHz RGB working on these sets, I suggest trying 180 ohm termination on your RGB lines and experimenting with different inline resistor values until you find the right combination. Just an idea.

[matt]

Yes, I have a 13" Sharp TV with a TA1268N that I've modded. It does work if it's set up as you described, with the higher value termination resistors. It also clamps the signal at too low a level so blacks are crushed unless you increase the RGB cutoffs in the service menu. It works OK, but the lack of brightness adjustment is a nuisance. I'd hope that going through the VGA circuit would yield better results.

[incrediblehark]

It’s a long shot but if anyone has a spare that they’d be interested in letting go of please send me a pm, I missed out back in the summer and am looking for a decent sized 480p crt. Thanks!

[Kayshott]

I too am going to take a long shot and ask if any of these are still available. This thread had me up all night!

[loopyeddie]

I am still loving my Hitachis. Not one problem since day one and use them frequently. Would still love a 15khz mod, but the line double works!

[loopyeddie]

I purchased the Irken Labs A1 Retro Scaler and couldn’t recommend it enough for use with these monitors. Not only does it display amazing looking 15khz with very little setup needed, it also will pass 31khz right through. Run anything you want into this scaler and it’ll work and look great. It’s a perfect pairing for these monitors.

[loopyeddie]

I’ve been using it with a Saturn, not with a supergun

[Josh128]

Hey Eddie! Glad to hear the monitors are still first class. Never heard of that scaler you are talking about. Is it similar in capability to a GBS-Control scaler?

[loopyeddie]

Yes, the idea is basically the same. I used the gbs-control prior to the Irken one. The gbsc honestly was amazing. I highly recommend it as well. I had one super minor gripe with the video quality - scanlines didn’t show up well on blue. No big deal. But I did have some weird adjustment issues. Basically the screen would roll over vertically and was very frustrating to adjust. A simple reset corrected it, but it keeps occurring. And finally, the are just too many parameters for me. The Irken scaler is crazy simple. Video in, video out. Choose rgb signal level (pcb vs. console), choose sync type (ttl vs. scart), and 4 or 5 scanline options. Plus the 31khz passthrough makes it so slick. I’m able to send video from, for example dreamcast at 31khz or Saturn at 15khz through an extron switcher to the monitor/scaler without having to unplug anything or change any settings. To top it off, the picture quality is phenomenal.

[8bitForLife]

ok just to recap what's the preferred way to connect 240p to this besides DC. I'm finally getting my set in a week or 2.

also has a 15hz mod been done yet?

I have a extron rgb 203 rxi / retro scaler a1 / ossc.

it's been so long iv had to wait a year for this tv so I'm not sure what all I need to get 15hz/240p working on it.

[Josh128]

For 15KHz you'll either need to use Svideo or composite, or a line doubler / scaler such as GBS-C / RetroTink/ OSSC into the VGA port. Of course the RT and OSSC will require an HDMI>VGA transcoder.

Ive not furthered my initial RGB mod attempt, which worked but was dim. IMO just get one of the above scalers and go into the VGA port and be done with it.