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

[loopyeddie]

I am finding that interlaced sources have jitter on the A1 scalers, but everything else works wonderfully. I’m considering picking up an OSSC - does it have a passthrough function if I send it a signal that is already in 480p? Or will I have to disconnect it?

[Einzelherz]

Apparently I missed all of this hoopla a few years ago but I must say I'm envious of those who got one and very impressed by Josh's work in helping out the community with some very awesome looking sets!

[loopyeddie]

I was an awesome hoopla and Josh was incredible. I bought 3 and wish I had bought 6.

[Josh128]

Just ran across this entry in Matt's CRTdatabase.com. I recognized the set as one from my Hitachi heist. Very nice informational format. I found this page while randomly googling flybacks + this model, I tried in the past and had no luck to obtain one, guess thats still the case.


Anyways, I thought it was cool. Still has "Kingsway Elementary" on it. This one made it from Louisiana to Hawaii in one piece, lol.

We need to add the 27MM30B to the database. Functionally the same but new mainboard revision with no bodges and different peripheral boards.


https://crtdatabase.com/crts/hitachi/hitachi-27mm20b

[Josh128]

New development for those whose sets had cracked speaker covers. My good buddy @OverlordManny has recently acquired a resin printer and it looks like it is much more capable of printing the intricate patterns required for the speaker covers than filament printers. He printed two simultaneously in 45 minutes and they look perfect. Just need to see how the fit is on one of my units and if its good, hopefully we'll be able to help a few folks out in this regard.

[maxtherabbit]

impressive result

[Josh128]

It is. My friend managed one decent print from a filament printer, then never could get another one done without a crash. I sent thchardcore the files to try to print himself and he never could get a good print even from a printing service.

My friend recently got a 12K resolution resin printer and wanted to try the design on it to see how it would do. Night and day difference. Printed two of them simultaneously in 45 minutes, first attempt. He used a resin that is supposed to be similar in strength and flexibility to PLA. No visible filament lines at all and feels tough yet slightly flexible.

This design purposely increased the size and therefore reduce the number of tiny holes in the front so that it might be possible to print with a filament printer. After seeing how easily the resin printer did it, I believe a perfect replica is possible if the model were redesigned with the smaller holes. This one looks great though, so its not worth the trouble. Just needs some paint and to be tack glued in place.

[matt]

For anyone who's using these TVs in 15 kHz mode, image quality can be greatly improved by disconnecting the velocity modulation board. Common in many higher end TVs from this era, this "feature" enhances black outlines and makes pixel art look weird. Unfortunately there's no way to disable it from the menus so you have to physically unplug it. I put instructions on the CRT Database page:

https://crtdatabase.com/crts/hitachi/hitachi-27mm20b

We need to add the 27MM30B to the database. Functionally the same but new mainboard revision with no bodges and different peripheral boards.

Of course! If you can send me some photos & other info I'll make a page for it.

[Josh128]

Matt, do you have before and after photos of disconnecting the VM board? I think thats going to be very subjective as to whether or not it improves image quality-- it greatly depends on the level of VM, which is not adjustable on these sets electronically AFAIK. I dont remember if theres a pot on the VM board that is adjustable. On my all my 36" Trinintrons, HD and SD, I sincerely think that VM level of 1 ( on a 0-3 scale ), looks best. Turning off looks softer than I prefer. I do agree that levels 2 and especially 3 looks like crap.


Also, are you sure it doesnt affect 31KHz mode as well? I say this because as good as all my 15KHz games looked in 31KHz mode via the GBS-C or 5X Pro, I didnt see much difference (other than richer color) vs just using S-Video in direct from a 15KHz source. Below is a small gallery of shots of NESRGB modded NES outputting S-video to the set that I took back when I first got these. Other than a slight bit of signal reflection seen just to the right of the images and the bit of vertical misconvergence, these looked fantastic in person and in the photos.

https://imgur.com/gallery/IYOnxuH

[matt]

Matt, do you have before and after photos of disconnecting the VM board? I think thats going to be very subjective as to whether or not it improves image quality-- it greatly depends on the level of VM, which is not adjustable on these sets electronically AFAIK. I dont remember if theres a pot on the VM board that is adjustable. On my all my 36" Trinintrons, HD and SD, I sincerely think that VM level of 1 ( on a 0-3 scale ), looks best. Turning off looks softer than I prefer. I do agree that levels 2 and especially 3 looks like crap.

Sorry, I didn't think to take some! Unfortunately the MMV is off the workbench right now as I have a pile of PC monitors to work on for a bit. So it'll be a little while before I can do that. It definitely made a difference, although the VM wasn't very aggressive. I'd guess it was equivalent to the "1" setting on a Wega.

I'm personally not a fan of VM and strongly dislike it on 2D games, although I sometimes turn it on for DVDs. So my opinion is somewhat biased!

Also, are you sure it doesnt affect 31KHz mode as well? I say this because as good as all my 15KHz games looked in 31KHz mode via the GBS-C or 5X Pro, I didnt see much difference (other than richer color) vs just using S-Video in direct from a 15KHz source. Below is a small gallery of shots of NESRGB modded NES outputting S-video to the set that I took back when I first got these. Other than a slight bit of signal reflection seen just to the right of the images and the bit of vertical misconvergence, these looked fantastic in person and in the photos.

https://imgur.com/gallery/IYOnxuH

No, it's not active in VGA. The picture looked identical before & after unplugging the cable. Also, according to the schematic the VM circuit is driven by the luma out signal from the jungle chip, which is missing in VGA mode.

I can see the VM artifacts in your screenshots. The black areas in the Zelda overworld mountains are fatter than they should be, and the blue outline on the Magic gauge is crushed, for instance. It's easier to spot after you unplug the cable and compare.

The ghosting to the right of objects didn't seem to be affected by the VM circuit. It was still there either way, but I could get rid of it by reducing sharpness.

[LDigital]

These sets look fantastic. I wish I could get hold of one in the uk

[Josh128]

@thchardcore

Shipping shows the package arrived, which is a little hard to believe as I shipped it Saturday. Did you get it?

[thchardcore]

Hi Josh. Yes, received super fast. These look so much better than the ones I had printed online.

Was locked out of account for 2 weeks, so just replied to your PM.

Thanks again.

[Josh128]

Hi Josh. Yes, received super fast. These look so much better than the ones I had printed online.

Was locked out of account for 2 weeks, so just replied to your PM.

Thanks again.

Awesome-- if you dont mind, when you get them painted and installed, post a photo!

[thchardcore]

Of course.