can i connect an LCD VGA monitor in place of a crt?

different mpu in the slot has the same result. its a tatung VT-1440S monitor, VGA . i would like to hook up a desktop vga monitor.

I don't know if this will work in your case, but you may want to check it out. I am sure there are similar items to do the conversion. I am using one like that to convert a non standard HP service monitor composit out put to a lcd monitor.

Arcade Game RGB/CGA/EGA/YUV to VGA HD Video Converter Board GBS8200.

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Yes. It should work. I do that all the time for old CNC machines that basically have a PC inside as a controller. Just be careful how you wire the video cable or adapter.

You can get a rebuild kit for your Tatung VT-1440S at: $16 total.

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i need to know what pins to use and not use.

thanks

Why, when you can easily fix the existing monitor?

Well, you have a schematic of the interface, so that should be easy.

Ok, I'll try to connect the dots. I'll guess(tm) that you have a matching 19 pin connector for the monitor and need to attach a DE15 connector to go to your random VGA replacement Monitor. If so, do NOT connect anything to pins 14 thru 19 on the monitor cable end because those are involved in supplying power to the monitor.

Monitor DE15 (VGA) 1 Blue 3 (BL video) 2 Red 1 (RD video) 3 Green 2 (GN video) 4 HSYNC 13 (horizontal sync) 5 Red Gnd 6 (red shield ground) 6 Blue Gnd 8 (blue shield ground) 7 Green Gnd 7 (green shield ground) 8 Digital Rtn 10 (digital ground) 9 VSYNC 14 (vertical sync) 10 Touch Rcv (see note 1) 11 Touch Xmit (see note 1) 12 GND 5 and shield gnd 13 GND 5 and shield gnd

Notes:

1. The game machine obviously requires a touch screen input to operate. While the VGA monitor will show something, there is an unknown as to how a random VGA montitor is going to produce the required and unknown touch screen signals. In any case, the wires from Monitor pins 10 and 11 do NOT go to the random VGA monitor.

1. I'm not sure about the various grounds on the VGA connector pins

6, 10, and shield. I'll need to tear apart a VGA cable to see how it's done. I don't have one handy, so you get to do that yourself.

1. Notice that many of the wires are shielded. You can build the adapter without using shielded cables. It will work, but probably show some noise and smearing. Good enough for a first test and you probably won't notice on a small monitor.

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Jeff Liebermann     jeffl@cruzio.com 
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Skype: JeffLiebermann     AE6KS    831-336-2558

the touchscreen is an overlay on the front of the crt. i dont want to attempt to repair the monitor until i know all the other functions of the machine work. it can be operated with buttons if the touchscreen isnt there.

thanks much

rect. the image is shifted to the left and cut off. there is a black verti cal bar, about 15% of the screen size in the right 3/4 of the screen . to t he right of that is the beginning of the image that is shifted to the left.

So, the video system is probably sending bad timing signals? This sounds like a screen format miscommunication issue.

VGA uses three pins to send screen capability data from the monitor to the video card, and that info determines whether you get 640x480 or 1280 x 800, or whatever. Older VGA uses different schemes, just to make things interesting.

Screen mispositioning often just means a bad video cable. I've seen it happen with DVI, too.

The original monitor seems NOT to be connected by VGA, it's possible the slot machine will just assume the CRT is the correct one to display whatever signals it outputs, rather than looking at EDID data the way a PC would.

will that affect what i'm trying to do?

i made up the cable as per jeff's chart, and the lcd monitor displayed a very nice image. now i can go thru the machine and test all its functions. with the image on the original monitor as described above, do you think a cap kit will do the trick?

thanks

It sounds like a phasing problem - its a simple fault to fix, but not simple to find the part.

Usually; the phase is sampled from a winding on the horizontal transformer. There's usually a high resistor in series with that signal on its way to the horizontal oscillator. If that's in a chip - its usually easy to trace the path to the transformer.

Another possibility is the scan energy recovery system, the left to centre part of the scan is driven by recovered energy - the horizontal transistor drives from centre to RHS, the energy is recovered at the end of that. A fault there usually causes cramping (horizontal linearity) but early onset faults can distort the waveform back to the phase discriminator.

Maybe; the video MODE information never gets confused when the ID pins are read, but if those AREN'T in use, the video output and the sync signals might be misinterpreted as the entirely wrong sync rate, or resolution. The description of the picture being offcenter of the screen does sound like a mode mismatch between monitor and video 'card'.

So, the monitor walks the picture off the left screen edge at 5 milliseconds, but the picture isn't completely sent until 8 milliseconds. The monitor just decided on the wrong horizontal sweep rate.

In the early days of multisync monitors, Apple and IBM and third parties all did the timing according to whims. Adaptation was a BIG issue.

Very good.

Of course, why else would I suggest it? I haven't fixed CRT monitor for at least 6 years. I didn't even know that there were re-cap kits available for CRT monitors. However, if it's anything like LCD monitors, replacing the caps will usually do the trick. Electrolytics don't last forever.

You might need to look into replacing the flyback if you can't get any hi-V and the rest of the horizontal sweep circuitry seems to be ok. Hard to tell from here.

Also, CRT's are potentially dangerous and can zap you without much provocation. Attach a clip lead to a big INSULATED screwdriver, ground the lead to the frame, and discharge the CRT tube before diving into the circuitry. Remember, you have but one life to give to your profession.

Never thank me before it's working. Bad luck and all that.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

rect. the image is shifted to the left and cut off. there is a black verti cal bar, about 15% of the screen size in the right 3/4 of the screen . to t he right of that is the beginning of the image that is shifted to the left. i took the monitor to a repair shop, and he says the monitor/chassis is ok . i'm not too sure about that. a different mpu in the slot has the same res ult. its a tatung VT-1440S monitor, VGA . i would like to hook up a deskto p vga monitor.

able with a female db-15 and individual pins on the other end.

When my buddy was in the vending business, I repaired several hundred of hi s monitors, many just like this one. I seem to recall a horiz phase adjust ment on the main board. Sometimes just tweaking this pot would lock in the picture.

If the board has never been recapped, it's time to do this. Go to Digikey and select low ESR high hour caps (I prefer Panasonic) and shotgun the boar d.

The phase comparator compares the sync with a pulse from a winding on the horizontal transformer. Its fed by a high value resistor - going high or open is a very common fault.

This happens very rarely but I've seen a cap to ground open on this line which causes the picture to shift.

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It was common enough on TVs, and I've seen it on a few VGA monitors.

With some TV makes/models - it made it onto the stock fault list.

cap kit did the trick, nice image now. way in the corner of the board was a leaker you couldnt see until it was pulled. thanks to all for your help

On old gear - some engineers do a cap kit anyway before getting down to fault finding (if there is any).

If the fault persists, there's a much greater level of confidence when you have to roll your sleeves up and hunt the elusive part.