Hi,
I am at my wit's end and don't know where else to turn, I hope someone out there smarter than I can help me out. I have an old Gildemeister CNC lathe and the CRT display has died. Cannot source a new part and it would be a waste to scrap an otherwise functional machine just because of a busted display. It has an odd video output in the form of a male 2 row d-15 pin connector. I have found a pinout description in the manual which would suggest that the video out is RGBHV and I would like to have this show up on an old VGA monitor. I have connected the D-15 output to the VGA input of the LCD screen via a GBS8200 board. As can be soon on the drawing of the output pins I have connected the R G B H and V pins along with their corresponding ground pins to the same on the VGA terminal block which goes to the VGA input of the GBS8200.
Problem is that I am indeed getting the gildemeister logo on the LCD monitor but only for a few seconds and very jittery, then it disappears and I get a black no signal screen. Occasionally I get an all green screen for 10-12 seconds then it disappears again. I could understand if I wasn't getting a signal at all or a continuous bad/distorted signal but this intermittent on and off has me baffled. I did notice that the CRT input on the busted screen has a small circuit on it with 2 ICs that are apparently Schmidt triggers. I don't know if these are needed for a VGA signal going to an LCD screen. I would be eternally grateful for any advice or guidance.
Regards
Mike
Link to photos below
https://drive.google.com/drive/folders/ ... tTTCQsJBTC
Help with RGBHV to VGA via a GBS 8200
Re: Help with RGBHV to VGA via a GBS 8200
Are you able to see the stock main menu of the gbs? should look like this and would display regardless of the input iirc, if it's not showing or only showing intermittently then the LCD doesn't like the output would be my guess. You can also try pressing the 'down/auto' button for 5 seconds to see if it can lock-in.
Re: Help with RGBHV to VGA via a GBS 8200
Stock gbs tends to lose sync unless you tweak some settings, plenty of info out there on the matter.
Your diode triggers would be a sync combining circuit.
Gbs would probably prefer a combined sync signal fed to the tall pins on the edge of the board. Could harvest the old circuit or make a sketchy one.
Tim Worthington has posted a few good solutions for combining sync.
Having said all this, 15k is very rarely found in the HV sync format, your cnc could very well supply this, but are you sure it's 15k?
Good chance it's a 31k signal that could feed direct to a VGA monitor or crt PC monitor.
Your diode triggers would be a sync combining circuit.
Gbs would probably prefer a combined sync signal fed to the tall pins on the edge of the board. Could harvest the old circuit or make a sketchy one.
Tim Worthington has posted a few good solutions for combining sync.
Having said all this, 15k is very rarely found in the HV sync format, your cnc could very well supply this, but are you sure it's 15k?
Good chance it's a 31k signal that could feed direct to a VGA monitor or crt PC monitor.
Re: Help with RGBHV to VGA via a GBS 8200
Thanks for the advice Syntax. I did indeed try to connect the RGBHV (and their respective grounds) outputs of the machine to the corresponding pins on a VGA connector and plug it directly into a screen but I only got a 'no signal' being displayed hence my try at putting everything through the GBS8200. I have no idea what's coming out of the machine, 15k or 31k and I don't have a scope to check it.
This morning I tried the approach of combining the H and V sync into a common csync based on a 2N3904 transistor and a few resistors using the method described on
https://www.cathoderayblog.com/converti ... s-control/
Now I have readable image on the screen and the intermittent 'no signal' has disappeared. The image however is very jittery (can't see it the photo because it's a still image but it is quite bad). The instructions for the GBS states in the troubleshooting section that an unstable image can come from having the GBS and the console (in my case the machine) on the same power supply. Indeed I was powering the GBS from a 5v USB Power supply plugged into a mains outlet that is built into the side of the lathe but when I plug this into a different mains outlet the flickering screen persists. I am inclined to believe that it is a grounding issue (I could be wrong) though as everytime I touch any of the pins on the GBS or the terminal block of the D-15 connector there is a noticeable change in the flicker pattern on the screen. Does anyone have any ideas as to what else I may try?
regards
Mike
This morning I tried the approach of combining the H and V sync into a common csync based on a 2N3904 transistor and a few resistors using the method described on
https://www.cathoderayblog.com/converti ... s-control/
Now I have readable image on the screen and the intermittent 'no signal' has disappeared. The image however is very jittery (can't see it the photo because it's a still image but it is quite bad). The instructions for the GBS states in the troubleshooting section that an unstable image can come from having the GBS and the console (in my case the machine) on the same power supply. Indeed I was powering the GBS from a 5v USB Power supply plugged into a mains outlet that is built into the side of the lathe but when I plug this into a different mains outlet the flickering screen persists. I am inclined to believe that it is a grounding issue (I could be wrong) though as everytime I touch any of the pins on the GBS or the terminal block of the D-15 connector there is a noticeable change in the flicker pattern on the screen. Does anyone have any ideas as to what else I may try?
regards
Mike
Re: Help with RGBHV to VGA via a GBS 8200
Yes I can access the GBS menu but the flicker persists regardless of the menu settings or if I press the auto button on the GBS board.
Re: Help with RGBHV to VGA via a GBS 8200
Hi,
So an update on the situation. I have tried a few different power supplies for the GBS including a battery bank but the flickering persists. This is currently my wiring
As you can see none of the ground pins on the machine side (3,5,7, 14 and 12) are currently connected. When I connect any of them to the ground on the GBS the flicker becomes orders of magnitude worse. The only ground connection between the GBS and the machine is the jumper between the transistor emitter pole via the 1k resistor and when I disconnect this completely there is no change to the flicker (neither better or worse).
I can see an image which is stable enough to actually operate the machine but the flicker is very annoying and makes the task very difficult so it would be great if I can get rid of it or at least reduce it to the point where it's hardly noticeable. It's not going to display any real graphics, just green text and numbers on a black background. I would be grateful for any hints or suggestions.
Regards
Mike
So an update on the situation. I have tried a few different power supplies for the GBS including a battery bank but the flickering persists. This is currently my wiring
As you can see none of the ground pins on the machine side (3,5,7, 14 and 12) are currently connected. When I connect any of them to the ground on the GBS the flicker becomes orders of magnitude worse. The only ground connection between the GBS and the machine is the jumper between the transistor emitter pole via the 1k resistor and when I disconnect this completely there is no change to the flicker (neither better or worse).
I can see an image which is stable enough to actually operate the machine but the flicker is very annoying and makes the task very difficult so it would be great if I can get rid of it or at least reduce it to the point where it's hardly noticeable. It's not going to display any real graphics, just green text and numbers on a black background. I would be grateful for any hints or suggestions.
Regards
Mike
Re: Help with RGBHV to VGA via a GBS 8200
https://imgur.com/a/mueoLnC
Use this simple sync combining circuit instead to rule out the transistor causing issues.
Make sure you have a good ground linked to the gbs. Sounds like the others are causing a ground loop. You only need 1 good ground connection.
Ommit D4, you don't need it. D3 on the diagram drops the sync level by .7 v you may need to ommit it. Or do the mod to drop the termination level on the gbs sync input. I can't remember what resistor value we use for that.
It will be documented on GitHub gbs-control
Use this simple sync combining circuit instead to rule out the transistor causing issues.
Make sure you have a good ground linked to the gbs. Sounds like the others are causing a ground loop. You only need 1 good ground connection.
Ommit D4, you don't need it. D3 on the diagram drops the sync level by .7 v you may need to ommit it. Or do the mod to drop the termination level on the gbs sync input. I can't remember what resistor value we use for that.
It will be documented on GitHub gbs-control
Re: Help with RGBHV to VGA via a GBS 8200
Thanks Syntax, I'll give it a shot. Just to clarify, when you say omit D4 do you mean that entire connection to 'enable' or just the diode (and if enable is required where is this connected to)?
As a side note, on the machine side of things I am getting a voltage between the hsync pin and it's ground pin of 3.6v. On the vsync pin I'm getting 3.8v.
Cheers
Mike
As a side note, on the machine side of things I am getting a voltage between the hsync pin and it's ground pin of 3.6v. On the vsync pin I'm getting 3.8v.
Cheers
Mike
Re: Help with RGBHV to VGA via a GBS 8200
No D4, it's more of a disable than enable we don't need it.
Try with d3 then without. With out will be ttl which the gbs is built for.
Try with d3 then without. With out will be ttl which the gbs is built for.
Re: Help with RGBHV to VGA via a GBS 8200
Hi,
So I got hold of some 1N4148 diodes and gave this setup a go
First with D3 then without. The image on the LCD screen overall appears to be better than with the transistor method I tried earlier although there is still quite a noticeable flicker, and omitting the D3 diode gives a better result than with D3 in place.
The odd thing is if I connect any of the ground pins from the machine side to the ground on the GBS 8200 the the flicker gets extremely bad, the best result is not having any ground connection at all in place, which I can't explain. Anyone have any suggestions?
Thanks
Mike
So I got hold of some 1N4148 diodes and gave this setup a go
First with D3 then without. The image on the LCD screen overall appears to be better than with the transistor method I tried earlier although there is still quite a noticeable flicker, and omitting the D3 diode gives a better result than with D3 in place.
The odd thing is if I connect any of the ground pins from the machine side to the ground on the GBS 8200 the the flicker gets extremely bad, the best result is not having any ground connection at all in place, which I can't explain. Anyone have any suggestions?
Thanks
Mike
Re: Help with RGBHV to VGA via a GBS 8200
Is it possible your cnc has a live chassis?
Re: Help with RGBHV to VGA via a GBS 8200
I just measured the voltage across the sync pins and the ground pins on the plug, (3.5v). Then I measured the voltage between the sync pins and the chassis and I get the same 3.5v so it would appear as if that were the case.
Re: Help with RGBHV to VGA via a GBS 8200
I found some additional info in the manual,
It's in German but it would appear to be 21kHz video signal with the Hsync and Vsync signals negative ttl level and the RGB in the positive and 330ohm input resistance. The sentance highlighted states that the monitor Earth must be isolated from the chassis. The LCD monitor im using is plugged into an extension lead going to a wall socket on the other side of the building, likewise the GBS is getting its power from a wall socket not connected to the machine.
Regards
Mike
It's in German but it would appear to be 21kHz video signal with the Hsync and Vsync signals negative ttl level and the RGB in the positive and 330ohm input resistance. The sentance highlighted states that the monitor Earth must be isolated from the chassis. The LCD monitor im using is plugged into an extension lead going to a wall socket on the other side of the building, likewise the GBS is getting its power from a wall socket not connected to the machine.
Regards
Mike
Re: Help with RGBHV to VGA via a GBS 8200
I finally got rid of the flickering screen. I tried the method described here
https://chrisumbel.com/article/video-sync-combiner/
Using a CD4077be IC wired to a 5v source (took power from the GBS board as this is being powered by a 5v source) wired pins 12 & 13 to the machine Hsync and Vsync pins, soldered a 1k resistor to the pin 11 output and this went to the S terminal on the GBS and the flickering is gone (or at least barely perceptible.)
Thanks for all the tips here, wouldn't haven't gotten as far as I did without them. Looks like the old girl won't go to the scrapheap just yet.
Regards
Mike
https://chrisumbel.com/article/video-sync-combiner/
Using a CD4077be IC wired to a 5v source (took power from the GBS board as this is being powered by a 5v source) wired pins 12 & 13 to the machine Hsync and Vsync pins, soldered a 1k resistor to the pin 11 output and this went to the S terminal on the GBS and the flickering is gone (or at least barely perceptible.)
Thanks for all the tips here, wouldn't haven't gotten as far as I did without them. Looks like the old girl won't go to the scrapheap just yet.
Regards
Mike