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Author Topic: Wei-ya 828HB chassis with Beijing Jile 27" tube issue  (Read 1921 times)

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madg

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Wei-ya 828HB chassis with Beijing Jile 27" tube issue
« on: December 26, 2010, 03:02:18 pm »
Hi guys

I have just built a cabinet to run MAME off a PC (using the ArcadeVGA PCIx card). The tube and chassis came separately, but I bought them at the same time from the same place, so my assumption at this point is that the chassis matches the yoke resistances and impedances  :). I know the chassis is a Wei-ya 828HB (shown on the neckboard, image 13), but unfortunately I have no way of recognising what the model of the tube is. There is not one sticker with a recognisable model and make. All I can say is that it's a 27" tube and the company is Beijin Jiles Electronics for all I can tell. Made in China, what can I say! :P Supposedly both were new. I hooked it all up, but all I get is a non-recognisable fuzzy white image, with slanted horizontal lines scrolling up, which is a lot like a out-of-sync picture, but this one has no recognisable colors. I've attached a picture of this (image 14). I've tried playing with the various potentiometers, and they do affect the picture, but they definitely don't bring out any sort of recognisable picture or colors :-\ . I've managed to keep those moving horizontal lines steady, but then they run off again.

I have a couple of questions:

- When I first turned the whole thing on, I heard this electrical crackling / humming noise for about 5 or 10 secs
(like a very small tazer), then it disappeared. It wasn't too loud, but being a newbie, it still gave me the jitters   :o. At first I got a bit scared, but then after it went away I didn't think much of it. No smoke or burning smell, and it hasn't made it since that first turn on. Is this normal for a brand new chassis and tube? I thought maybe new tubes need to be run-in or something on their first switch-on. I'm mentioning this because this maybe damaged something on the tube or chassis.

- The grounding loop wire that runs around the tube, does it have to run all around the tube, or is that not so important as long as it touches the metal surrounding the front of the tube? I'm asking this because the one on my tube broke when installing the tube in the cabinet, and I just couldn't make it run all around the tube again for some reason, so it only runs along the bottom and left side at the moment. Is that a problem? It still touches the metal around the tube as far as I can tell. I attached a picture of this wire (image 7).

- The grounding wire is connected to the neckboard, and there is clearly a ground connection from neckboard to chassis; connector label E (for Earth I presume) on both neckboard and chassis. But the chassis is connected to power via a 2-wire isolation transformer (image 9); there is no ground connection. Moreover, there is no clear connection for ground on the chassis even if I wanted to connect one. The only ground 'input' is from the video signal connection (from PC), but I assume this is more of the signal ground, rather than safty ground. Do I have to connect a safty ground connection to the chassis and tube somehow? By the way, where I live, the plug points are three-pronged with one prong being ground. This however is not connected anywhere on the monitor/chassis circuit since there is no connection for it.

- If I leave the monitor on for a couple of minutes, I start hearing this faint burning noise, you know like a small smoldering fire, but a very very soft noise which probably wouldn't be heard if I was playing a game. I can't really smell any burning or smoke though. Is this normal, maybe because the tube is still new and it needs to be run-in somehow?

- Any idea where I should start looking to work out what the cause of the image I'm getting is? I mean, I'm pretty sure power should not be an issue since the screen turns on. But could it be possible that the wrong amount of power can cause such a picture? I do want to do some kind of continuity tests of the video connector from VGA cable to neckboard, but is that safe to do without discharging the tube (power off though off course!) and would it be a good test?

- If I disconnect the power, do I still want to discharge the tube if all I want to do is say test the various eletronics around the chassis with a multimeter? How about measuring the resistance across the yoke connections (if I needed to that is)? And testing components on the neckboard, like the continuity test I want to do? And taking out the neckboard?

- I'm quite wary of the whole tube thing, and any small noise makes me jump  :o. Are there certain things that are 'normal' and I shouldn't be worrying about? eg. slight electrical hums, slight static noises, etc...

- The neckboard is a 8-pin (judging from the connection on the chassis which has 8 wires), but the tube neck had one less pin. Is that normal? I'm pretty sure I fitted it on correctly, I mean the shape of the neckboard connector doesn't allow for errors  :-\ And surely if the neckboard had the wrong number of pins it wouldn't be able to connect to the tube neck?

I am probably going to return the tube and chassis where I bought it and ask them to test the whole ensemble and set it up for me, but I thought first let me see if I can't get any answers from the interweb, since they'll probably only re-open in the new year.

I've attached a couple more pictures of the chassis (image 5), the neckboard (image 13), the yoke (image 4), the video connection on the chassis (image 6) and the video amplifier from the PC VGA cable to the chassis (image 10)

Thanks in advance for any insight you can give me!
« Last Edit: December 26, 2010, 03:06:02 pm by madg »

grantspain

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Re: Wei-ya 828HB chassis with Beijing Jile 27" tube issue
« Reply #1 on: December 26, 2010, 06:21:17 pm »
nasty cheap chassis they are,almost all of your problems are down to the screen volts being way too high(next to focus on flyback transformer)
try that first
oh btw these little shits hold a nice charge on the crt as there is no bleed resistor in the flyback circuit

madg

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Re: Wei-ya 828HB chassis with Beijing Jile 27" tube issue
« Reply #2 on: December 27, 2010, 01:19:50 am »
I just tried playing with the screen volts, I could essentially lower the brightness, even up to the point where it just doesn't display anything anymore on the screen, as if it was off (is that normal?  ???), but the scrambled fuzzy picture wouldn't go away even at low voltage / brightness.

Regarding the bleed out resistor you mentioned, if I run my hand over the glass of the screen when it's on, the hairs on my hand rise up, but when I turn it off, after a few seconds they don't anymore. Doesn't this mean that it doesn't hold as much charge anymore, or doesn't that mean anything really?

grantspain

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Re: Wei-ya 828HB chassis with Beijing Jile 27" tube issue
« Reply #3 on: December 27, 2010, 04:41:16 am »
the earth braid should encompass the entire crt and be tight against the dag
as for the static on the screen-don't read anything into that

I am quite sure that chassis is matched to that tube,maybe you need to make more adjustments as i have never seen a chassis work straight away without the need for any adjustments