Anyone here using an Xvga universal video converter on a CNC?

Here's the short version - I bought a universal CNC video converter from Gonbes in China. There are other sources but Gonbes seems to be the manufacturer or distributor. I can't get good video from it and Gonbes has been not help. Has anyone here used one and had good results? I've seen them mentioned but never much information along with the mention.


I connected this one first to a Dynapath Delta 20 that has composite monochrome video output, and connected a standard Samsung 19" VGA monitor to the adapter. Things looked good at first, but when I changed screens in the CNC, the first screen stayed on display and the second screen showed up also, slightly dimmer. Changing screens on the CNC would change the ghosted screen, but not remove the first screen. The only way to get a second screen to display clearly is to power down the converter wait a few minutes and power it up again. Then you can see whatever screen is output as the primary display. Changing to another screen again shows 2 screens.

Adjusting the input parameters in the setup menu makes a mess of the display, eventually displaying garbage that won't go away until the converter is powered down and allowed to rest. Reconnecting it too soon just shows the garbage screens again. The longer power is connected the worse the display gets, and the only fix is to power down and walk away for 1/2 hour or more. I tried a completely different vga monitor (A/R and size) with the same result


Gonbes blamed this on the Dynapath control, saying it was not compatible with the converter and telling me to get a technician to test the video frequency with a scope, or a mulitmeter. I have a mulitmeter with a frequency capability, but no way to separate the H and V frequencies. so that's useless. The converter is rated for 12 to 40 Khz H frequency. The Dynapath is 20-21, the Deckel is 15.64, the cincinnati is 15.82.


So I connected it to 2 other CNCs to test it, a Deckel Dialog 4 and a Cincinnati 850. The Deckel has a composite output on the bottom of the control console intended to connect to an external monitor and should be quite easy to convert, the Cincinnati 850 has an internal composite connection from the motherboard to the display in the operator console.

I got the same results from both of those controls. Photos attached.


I've been beating this to death for a month, Gonbes has been no help except to request more tests and experiments like adding ground wires. They insist their converter is not defective and that all three of my controls are the problem. They offered to refund half my purchase price and suggested I should sell it to someone else that can use it.


So I filed a paypal case. Gonbes offered to refund my purchase price less shipping and paypal fees IF I withdraw the paypal case AND destroy the adapter first and send them photos of it destroyed. I then escalated the case to paypal for resolution, they made the same offer of purchase price refund only, I have until 3/15 to accept that or refuse it and see what paypal decides to do. The difference is only about $25, but I'm REAL annoyed about all the time I've wasted over the past month on this and the zero help I've received and I'm in the mood to beat this dead horse to pulp.


So gentlemen of PM, has anyone here used a converter like this successfully? What do you think is happening here, and what do I need to do to get a VGA monitor working on one of these machines? Is there something I'm completely missing about this? The Dynapath is old and getting really hard to see the monitor on (monitor faces a bank of windows) and a larger one would make the machine much nicer to run. The Deckel monitor is working fine, but a larger secondary screen would make the machine much nicer to operate because it's a large machine and we're often fairly far from the console using a remote handwheel. I'm attaching a few photos to show what happens, If they aren't clear I have LOTS more photos.

More photos in the next post.

I have one of those, bought it quite a few years ago now but never did put it to use. I bought it to put on a dual screen ultimax 2 Hurco but couldn’t get it to work properly on the machine I bought it for. FWIW I tried it out on a few different machines and it worked perfectly on three out of four video sources that I tried. Gildemeister epl and Fanuc OT worked perfectly, as did the graphics screen on the hurco, but the text screen on the hurco was a no go, something screwed up with the horizontal sync - only started drawing the image halfway across the screen and wrapped/ghosted terribly over on the left side. No amount of adjusting or changing settings would make it useable and I gave up. I intended to try a hardware sync inverter on the input but never got around to it. The converter itself did seem like a pretty decent bit of kit. Might give it another go some time as I still have one old hurco running yet, but the screens are ok on that one, so incentive is missing for now...

I typed that up on my phone late last night, back in front of a computer this morning so I'll elaborate a little.

I did not use composite output from the control (none of mine had such an output) like you have tried. The colour sources I tried (gildy/fanuc) used RGBHV to the original screen so that's what I connected to the converter. The monochrome sources (the hurco) are TTL level video with seperate horizontal and vertical sync to the original screen, and that's also what I connected to the converter.

It is sensitive to the inputs being grounded properly. In each machine I tried the original cable to the original screen had several common grounds, and I connected these to the body of the BNC connector on the converter. It will usually display an image without adequate ground, but it will be very noisy and unstable if it appears at all.

On the monochrome TTL sources I jumpered the video signal across each of the RGB inputs on the converter, resulting in a clean white on black image. Unfortunately as I mentioned above I just couldn't get the text screen on the Hurco (the one I really needed to work) to sync properly.

The converter itself has a hidden parameters screen with many available settings, but they are not labelled on the OSD and I was unable to find documentation for them, so unfortunately that's not helpful in the slightest.

gregormarwick said:

It is sensitive to the inputs being grounded properly. In each machine I tried the original cable to the original screen had several common grounds, and I connected these to the body of the BNC connector on the converter. It will usually display an image without adequate ground, but it will be very noisy and unstable if it appears at all.

Click to expand...

I have one of those units that I had setup for a backup (anticipating a monitor going at some point) and I had similar issues that was due to grounding problems. I had no luck with the "Video IN" connection, but rather had to use the separate RGB Inputs with separate grounds...

Just noticing you have no connections to V or H ??

The dynapath uses a single wire composite video signal.

I would ditch the coax and wire the composite and ground into the DB9 port. The converter should have a pigtail.

What's the specific model number? Link to a manual? There seem to be different versions, and I'm not seeing composite video input on some of them, just composite sync.

Chip Chester said:

What's the specific model number? Link to a manual? There seem to be different versions, and I'm not seeing composite video input on some of them, just composite sync.

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It's a GBS 8219, sold under several names. Gonbes is either the mfg or distributor. Here's a manual - http://redd103.ipage.com/crtretro/GBS-8219.pdf

ewlsey said:

The dynapath uses a single wire composite video signal.

I would ditch the coax and wire the composite and ground into the DB9 port. The converter should have a pigtail.

Click to expand...

I started with that and couldn't get any combination of pigtail wire connections and grounds to display anything. That's when I went to the coax connection. I just tried the DB9 again today with the Dynapath because of your suggestion and still got nothing.
All three of these machines are composite coax only, no other wires to connect to. My other machines are normal VGA, can't use them to test. The only other video source around here is a 400TVL security camera and that just produced garbage on screen, I don't know what its' output is.

SteveEx30 said:

I have one of those units that I had setup for a backup (anticipating a monitor going at some point) and I had similar issues that was due to grounding problems. I had no luck with the "Video IN" connection, but rather had to use the separate RGB Inputs with separate grounds...

Just noticing you have no connections to V or H ??

Click to expand...

There's only a single output wire from any of these machines. I read here on PM that means you use Sync On Green for the sync signal (just about everything I know about this I read here on PM) The G/Y connector is the only one that produces a display, one mode is SOY and one is SOG, the SOY with YUV. YUV with SOY worked best on the Deckel and is also what came up automatically. I suspect that the Green conductor and Ground in the DB9 pigtail would equate to the G/Y coax connector but connecting to them has no effect

Gonbes hasn't mentioned anything about needing more than one wire connection to work, and I've told the woman I'm emailing with that I can't separate the H&V frequencies because of them being delivered by one wire.

gregormarwick said:

I typed that up on my phone late last night, back in front of a computer this morning so I'll elaborate a little.

I did not use composite output from the control (none of mine had such an output) like you have tried. The colour sources I tried (gildy/fanuc) used RGBHV to the original screen so that's what I connected to the converter. The monochrome sources (the hurco) are TTL level video with seperate horizontal and vertical sync to the original screen, and that's also what I connected to the converter.

It is sensitive to the inputs being grounded properly. In each machine I tried the original cable to the original screen had several common grounds, and I connected these to the body of the BNC connector on the converter. It will usually display an image without adequate ground, but it will be very noisy and unstable if it appears at all.

On the monochrome TTL sources I jumpered the video signal across each of the RGB inputs on the converter, resulting in a clean white on black image. Unfortunately as I mentioned above I just couldn't get the text screen on the Hurco (the one I really needed to work) to sync properly.

The converter itself has a hidden parameters screen with many available settings, but they are not labelled on the OSD and I was unable to find documentation for them, so unfortunately that's not helpful in the slightest.

Click to expand...

Do you mean this OSD screen or is there another one I haven't found?



I'm game to try another one if this one is just defective, but I don't understand video enough to know, and the mfg insists they've never sold a bad one so this one can't be defective.

Well, the manual says nothing about being compatible with a composite video signal, mono or color. This may be Reason 1 the box is confused.
This site: GBS-82XX experiments – Something interesting is under way
makes mention (in red, halfway down) that CVBS (composite video blanking sync) will work when sent into the sync input. Are you connecting your signal to the H/CS input? (Don't know if there are menu choices associated with that.) If so, try un-terminating it (change the 75-ohm option in the menu shown to zero/none/unterminated/whatever-it-says.) Because that's what it says in red at the end of the sentence on the page referenced above.

(See Composite video - Wikipedia for more about the video signal.)

However, your Dynapath appears to have a monochrome video out, which most likely won't have color burst in it. So that may be Reason 2 the box is confused.

Your Dynapath may not switch signals cleanly, or it may have variations in the video signal (that a monitor doesn't care about) that cause the box to freeze frame the last known good video (a very common design approach), and it doesn't know how to deal with that condition otherwise. So, Reason 3. Jury deliberation on whether this is a design failure would hinge upon the fact that you're sending it a signal that is not specifically supported in the mfg. documentation, and sending it monochrome instead of color (Reasons 1 & 2). So yeah, it doesn't seem to work, but they didn't say it would in writing, either.

Phone support may not be schooled on non-standard undocumented features of the chipset, which happen to still work somewhat because engineering left them in.

There are composite to VGA adaptors out there for peanuts. Well, $20 in peanuts. Here's one:
Amazon.com: SLLEA RCA Composite AV S-Video to VGA Converter Box for DVD DVR VCR Monitor Cheap: Home Audio & Theater

This one is interesting in that it not only has composite video in, but it has S-Video in as well. S-Video separates luminance (the black and white signal) from the chroma information. It is pretty easy to hack a cable to put just luminance into the S-Video input, which could come from a monochrome video output like the Dynapath.

Have I done this with a Dyanpath? Nope. Can I guarantee the $20 box will? Nope, haven't had a need to try. But at least it's designed to input a composite video input (which most folks will assume is color, with burst). The good thing is it's not expensive to find out.

There also may be other boxes out there that exist to do exactly what you want to do, but the seller will likely charge for discovering that they will... making it somehow $pecial.

I have a similar box to your original box, but made by someone else, in a different case. I'll take a look to see if the menu is the same, in which case I could do some checking later this evening. Don't have a Dynapath handy, but do have a few video sources that might work.

Do you have any monitor that has yellow RCA plug inputs for video? Or even a new or old TV set that supports that? That would give you an idea of whether the various signals you're trying to view are close to broadcast standard baseband video, be it mono or color.

And re: "Gonbes hasn't mentioned anything about needing more than one wire connection to work, and I've told the woman I'm emailing with that I can't separate the H&V frequencies because of them being delivered by one wire."

...Hopefully you mean one cable, as in center conductor plus ground, (terminating in a BNC connector) rather than a single conductor, stuck into the center of the BNC input. These signals need a ground to work.

Chip Chester said:

There are composite to VGA adaptors out there for peanuts. Well, $20 in peanuts. Here's one:
Amazon.com: SLLEA RCA Composite AV S-Video to VGA Converter Box for DVD DVR VCR Monitor Cheap: Home Audio & Theater

This one is interesting in that it not only has composite video in, but it has S-Video in as well. S-Video separates luminance (the black and white signal) from the chroma information. It is pretty easy to hack a cable to put just luminance into the S-Video input, which could come from a monochrome video output like the Dynapath.

Click to expand...

I have that exact unit. doesn't work on either the Dynapath or Deckel, shows nothing except the OSD menu. Haven't tried it on the cincinnati because I don't need a monitor for that, happy with the CRT, was just using it to test the box. I believe the incoming H frequency is too low for it to decode, have seen units like that mentioned here in the past as not working in this kind of application.

And re: "Gonbes hasn't mentioned anything about needing more than one wire connection to work, and I've told the woman I'm emailing with that I can't separate the H&V frequencies because of them being delivered by one wire."

...Hopefully you mean one cable, as in center conductor plus ground, (terminating in a BNC connector) rather than a single conductor, stuck into the center of the BNC input. These signals need a ground to work.

Click to expand...

Yes, one cable, sloppy reply on my part.

I'll look at the other items ASAP. I believe I do have a TV with RCA jacks.

I think have some monitors around here I don't need. One 9" closed-circuit one, and a few other computer monitors of CGA era, I think. Obviously, repair on old stuff gets harder to come by, but they work now.

Also, there's an outfit here in town called the Early Television Foundation -- basically an established museum of the oldest-tech TVs that existed (pre-war, mechanical things) and a fledgling CRT re-build operation. One of their recent purchases netted a bunch of CRTs for both TV sets and "non-TV" applications, like kiosks, proprietary displays, etc. I can try to find a list of those tubes/monitor chassis (whichever they are) that perhaps some folks can put to use. But in general, CRT monitors can be a little more forgiving of unusual signals, due primarily to their adjustability and somewhat looser tolerances than a digital device.

Milicron had some experience with lower-than-average frequencies and LCD displays for one of his projects. You might try searching his posts for the saga. I think he was trying to replace a Hitachi proprietary LCD with something more generic/cheaper, and found one that was low-freq tolerant.

Thanks, I spent a lot of time searching here and found most if not all of the LCD swap posts from many posters including Milacron. I don't think any had a single composite cable output, so I bought this on a hope for the best chance, figuring if it didn't work on the Dynapath it would work on the others, Now i don't know where I stand. One seller sells a stock size LCD replacement, and also sells this converter, but won't tell me if the converter works on the Dynapath. I want a larger monitor if I'm going to replace it, that's why I didn't spring $800 for the bolt in replacement.

Dynapath themselves haven't addressed this, Paul told me it's because they had ~ 400 standard CRTs built and have plenty on hand, and aren't inclined to make an LCD at this time.

Mud said:

Gonbes blamed this on the Dynapath control, saying it was not compatible with the converter and telling me to get a technician to test the video frequency with a scope, or a mulitmeter.

Click to expand...

This was for a 5, not a 20, but I had a separate manual for the monitor. I think it was made by Setchell-Carlson ?

Anyway, the manual had a full and complete description of exactly what the monitor required. I think it even had circuit diagrams.

From struggling a little with graphics and weirdo monitors (T221 here at the moment), I can tell ya if everything is not exactly right, it ain't gonna work. Just a couple pixels too many or too few of blanking can totally mess up the display and do weirdo stuff you don't expect.

So I'd try to get exact specs before I got too deep into this.

Mud said:

Do you mean this OSD screen or is there another one I haven't found?

Click to expand...

There is another one, hidden, accessed by powering up the unit with some combination of buttons held that I can't recall. Like I said it's not useful without documentation and I could never find any, there are a huge number of editable parameters, none of them are labelled as to what they do.

If the original built-in screen on your machine is also composite (i.e. you have zero usable video sources on the control that have seperate sync), then your best course of action would likely to be to use a composite to vga converter as suggested by Chip Chester, or if for some reason that doesn't work to use a composite to RGB (sync on green) converter along with your existing converter.

gregormarwick said:

or if for some reason that doesn't work to use a composite to RGB (sync on green) converter along with your existing converter.

Click to expand...

This turns up from many sources when searching for composite to RGB converter. Composite S-Video to Component Video RGB Sync On Green Converter
i'm wondering if it will have an input frequency requirement that would prevent it from working with the CNC composite output?

Maybe compare the specs for these replacement CRTs:
Industrial Monitor- 9" Monitor DYNAPATH
to the acceptable inputs to the units you're considering.

Or better yet, send the supplier that link and ask if their box will accept and display the same inputs these monitors get. That way you don't have to become an overnight expert.