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

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loopyeddie
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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?
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Einzelherz
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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!
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loopyeddie
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by loopyeddie »

I was an awesome hoopla and Josh was incredible. I bought 3 and wish I had bought 6.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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.

Image


Image
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maxtherabbit
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by maxtherabbit »

impressive result
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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.
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matt
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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

Josh128 wrote: Fri Jun 16, 2023 11:22 pm 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.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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
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matt
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by matt »

Josh128 wrote: Fri Feb 16, 2024 11:21 pm 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.
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LDigital
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by LDigital »

These sets look fantastic. I wish I could get hold of one in the uk
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Josh128 »

@thchardcore

Shipping shows the package arrived, which is a little hard to believe as I shipped it Saturday. Did you get it?
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by 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.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Josh128 »

thchardcore wrote: Sat Mar 16, 2024 10:54 pm 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!
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by thchardcore »

Of course.
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loopyeddieagain
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by loopyeddieagain »

I have 3 of these to sell. I can no longer log into my old account (loopyeddie) though. Anybody need one of these babies?
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by loopyeddieagain »

Ok, it looks like I can get into the selling forum now. I’ll be listing 3 of these and I’m not looking to get a fortune, I just need them gone. They are fantastic, I just need the space.
Leoraider
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Leoraider »

I need just one or two flyback, really I do not want see any of those units dismantle but if you have any tv with defect or broken tube then I will purchase just the Hitachi flyback
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by thchardcore »

I have a complete PCB from a unit with a really scratched up tube that I was not able to save (yet). Would you be interested in buying the whole thing? I could use the space.
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matt
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by matt »

thchardcore wrote: Sat Aug 24, 2024 4:26 am I have a complete PCB from a unit with a really scratched up tube that I was not able to save (yet). Would you be interested in buying the whole thing? I could use the space.
If you're going to part out this TV, would you be interested in selling the yoke? One of mine is a little off and I could use a spare.

I'd also take the spare chassis if the other buyer isn't interested.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Josh128 »

Mike, before dismantling the unit over scratched tube, I strongly suggest you attempt the dremel style tool + 1000grit - 3000grit - 5000grit dry sanding discs, then very low speed wet pad + wet cerium oxide final polishing. Im not exaggerating when I say you can remove literal gouges in the glass and restore it to perfect gloss finish QUITE easily and quickly. After doing it myself I was literally amazed at the results and how easy it was-- and if I had known that before I sold the first few at a discount due to having scratched tubes due to being shipped to me touching face to face, I would have fixed them and sold at full price.

That said, If you do decide to part out, I would like a mainboard either with or without a flyback. The newest unit that I got, the "Ultravision Digital" MM30B model, has some type of weird power issue where bright screens shrink the image noticeably and dark scenes expand it back. I played around with the power delivery section / voltage regulator and changed the neckboard out and was not able to resolve it.
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matt
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

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Josh128 wrote: Sun Aug 25, 2024 3:48 pm Mike, before dismantling the unit over scratched tube, I strongly suggest you attempt the dremel style tool + 1000grit - 3000grit - 5000grit dry sanding discs, then very low speed wet pad + wet cerium oxide final polishing. Im not exaggerating when I say you can remove literal gouges in the glass and restore it to perfect gloss finish QUITE easily and quickly. After doing it myself I was literally amazed at the results and how easy it was-- and if I had known that before I sold the first few at a discount due to having scratched tubes due to being shipped to me touching face to face, I would have fixed them and sold at full price.
+1 on the tube polishing. I've managed to restore monitors that were literally dragged face down across the pavement. It takes some effort & practice but you can get it looking as good as new.

Although personally, I've been using 4" wet sanding disks with shave gel as lube for initially grinding out the gouges, followed by cerium oxide.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Josh128 »

matt wrote: Mon Aug 26, 2024 7:09 am

+1 on the tube polishing. I've managed to restore monitors that were literally dragged face down across the pavement. It takes some effort & practice but you can get it looking as good as new.

Although personally, I've been using 4" wet sanding disks with shave gel as lube for initially grinding out the gouges, followed by cerium oxide.
What grit for the wet discs do you use? Do you step to finer grit before going to CO or just start with the finest grit to begin with? My process is all dry until the CO. I am careful to not overheat the area Im working when using the dry discs, because the heat can definitely build up with the finer grits.
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Leoraider »

thchardcore wrote: Sat Aug 24, 2024 4:26 am I have a complete PCB from a unit with a really scratched up tube that I was not able to save (yet). Would you be interested in buying the whole thing? I could use the space.
Yes I wat purchase the chassis, may I know the cose Huber of the Hitachi fly back? Is this : 2435048? Thanks!
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by matt »

Josh128 wrote: Mon Aug 26, 2024 2:30 pm What grit for the wet discs do you use? Do you step to finer grit before going to CO or just start with the finest grit to begin with? My process is all dry until the CO. I am careful to not overheat the area Im working when using the dry discs, because the heat can definitely build up with the finer grits.
I usually use 800 and 1500. 1500 seems to be easy enough to polish out with the oxide so I don't need to go finer than that. Sometimes I can get away with just 1500, but it doesn't cut fast enough to deal with really deep scratches & chips.

My main motivation for wet sanding is to reduce dust, although temperature control is a bonus.
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Leoraider »

thchardcore wrote: Sat Aug 24, 2024 4:26 am I have a complete PCB from a unit with a really scratched up tube that I was not able to save (yet). Would you be interested in buying the whole thing? I could use the space.
May I know tre code number of the flyback? Is this 2435048 or 2435047?

Thank you in advance!
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by thchardcore »

Going to have to get to storage to pull the board for Josh before I can answer you, but I will document it here.
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Josh128
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Re: Hitachi 27" 27MM20B Dual-Scan CRT TV??

Post by Josh128 »

thchardcore wrote: Wed Oct 30, 2024 11:02 pm Going to have to get to storage to pull the board for Josh before I can answer you, but I will document it here.
I could have sworn I posted it somewhere in this thread long ago, but I didnt see it through a cursory glance through.
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