Chinese CGA chassis

[haynor666]

I've discovered some chinese chassis on aliexpress. Anyone have experience with these ?
I have have some spare TVs to test but would be nice to get some more info about these hardware.


https://www.aliexpress.com/item/4000018945526.html
https://www.aliexpress.com/item/33014568145.html

[SuperMagoAlex]

Poor quality, there is no degauss circuit and they work at 110V.

[haynor666]

Any other options for me (living in EU)?

[lilshawn]

time machine. the time to get chassis of a good quality was about 13 years ago in 2011.

honestly, those chassis aren't THAT bad. they are designed kind of similar to the K7000, having a regulator and resistive dropper system for the different voltages the chassis needs, opposed to a switch mode power supply providing several rails. not without its own caveats... its going to need an isolation transformer...fairly fixable if stuff goes sideways on it...it's fairly unpredictable if the voltage fluxuates, since a SMPS chassis uses current feedback to automatically adjust the voltages, keeping them steady.

as mentioned, this monitor is 110v, so you not only do you have to have an isolation transformer, but a 240 to 110v one. (since you are in the EU) to drop your line voltage down.

"wei-ya" makes some of the more decent chassis out there that are multi voltage compatible (as they mostly use SMPS) but they are also few and far between these days, occasionally you do run across them for sale. if you aren't in a hurry hold out for one of those.

depending on your needs and your tube/yoke combo you got going on, you may be able to steal one off another monitor (perhaps get a deal from someone with a busted tube selling off a chassis) but an makvision M2929, C3129 or wei-ya CH-666 (basically all clones of each other) will do VGA resolutions and can be modded to work for a fairly wide variety of yokes (within reason). perhaps a WG K7400/7500 chassis could be modded to work with your combo.

to effectively choose one, you'd have to measure the inductance of the yoke you plan to use with an LCR meter, otherwise if you blindly choose one... you chance blowing up a h or V drive with a mismatched tune.

[haynor666]

I have couple of EUR TVs, all actually with SCART but position and size of picture cannot be easy regulated that's why I started to thinking about using arcade chassis on standard TV tube.


About this specific chinese chassis -  need 1 V just like ordinary arcade monitor or 0,7V? There isn't any info even about how to connect this chassis to JAMMA or PC.

[Zebidee]

I think it is not worth the effort to use the cheap chinese chassis with the Euro TV tube.

I have travelled this path before, over 5 years ago. I bought 4 Chinese Wei-Ya 1820R (iirc) clones to use with some cheap 20" Chinese CRT TVs I'd obtained new-in-box, but couldn't RGB mod (they have an all-in-one jungle chip that incorporates OSD functions internally).

Anyway, the clone Wei-Ya chassis worked well enough with the tubes I guess, but the high voltage regulation was for ---steaming pile of meadow muffin---. In particular they never handled fast bright/dark changes very well, "blooming", there seemed no way to improve it. I tried several tubes, but it just seemed to be part of the design.

So I gave up on the Wei-Ya clones, they were pretty mediocre. Went back to using the tubes with their original TV chassis (the officially called "China TV" chassis, I ---steaming pile of meadow muffin--- thee not), as these are actually pretty good for what they were.

This experience is part of what prompted me to work on developing the GreenAntz RGB -> component transcoder project, because component-modding these TVs was easy enough, but RGB-YUV transcoders were expensive then. Ironically, now you can now buy cheap Chinese ripoffs of our oldest transcoder prototype designs, but they have the same issues as our earliest prototypes too. What can I say   

Anyway Haynor, I reckon you might be better staying with original SCART TV. I've used plenty in arcade cabinets before. The Euro TVs are usually be higher quality than most. It is RGB already, and the SCART connectors are easy to hack. You already have the right voltage there at the wall. If using CRT_emulator, it should be possible to customise your monitor presets to minimise overscan and adjust position somewhat for most modes. Often helps if you can access TV service mode, but not always necessary.

Oh yeah, and if using the Chinese chassis you'd need step-down ISOs for each monitor... or a step-down AND an ISO... so add that expense on top, and don't forget increased power usage (put your hand on top of the ISO after it's been working for a while, to feel how warm they get).

Reconsider trying SCART again, and maybe trimming monitor presets (or using ArcadeOSD) to minimise overscan etc. I can give you some pointers if you need.

[haynor666]

I'm currently on two SCART TVs. Together with groovymame/ArcadeOSD and it works quite nice. The pain is however to set everything - loots of time. Such chassis is potential option to improve this situation but all the hints You gave me I think it's not worth to invest money.

[Zebidee]

Maybe your experience would be different Haynor, with a different chassis. Just don't expect to find pearls among swine.

So yeah if the TV works just stick with it. I've used a few Euro SCART TVs as arcade monitors, they are generally good quality and, back in those days (10-15 years ago), you could get them for a song. Some great experiences but, like you say, sometimes can take "loads of time" to get settings right as each TV is different to the next.

It might be worth chasing down a refurbished K7000 or similar from a tech - then they can advise you about tube choices and support you through the tube swap. Maybe Lilshawn can give you some pointers.

I have had some good experiences matching quality Euro ex-TV tubes (Philips tubes from ~2000 era with bonded yokes are excellent) with Sharp Image monitor chassis. That was with direct support from JOMAC (Joey) who sold and services them. They are great chassis and I got outstanding results, probably best I've ever had with a 15khz arcade display, but AFAIK they aren't available anymore unless you can find one on the seconds market.

[Zebidee]

Mike Jensen reviews a Chinese 25" chassis. He seems to have had a relatively good experience. Don't know if it is the same as the one you were looking at. He paid US$90 for it.

He used a known good Hantarex Polo arcade monitor tube, and mentions some other known-good tubes. No discussion of stuff like impedance/inductance matching, or getting the right neck connector.

[lilshawn]

most of those universal chassis will work with a pretty wide variety of yoke impedances at low resolutions like 15k... most of the time you end up with a width you can't possibly make any wider or narrower... and all you'd have to do is  try a couple different values of poly cap on the horizontal section to find one that makes it closer.

things need to get a little closer with the yoke impendences when it comes to 31k and up resolutions.