Cable to connect a color video monitor to an VT240

[spiceminer]

Dear all!

I assume I can get color graphics from a VT240 when I connect a color monitor to the 15pin video connector?

Unfortunately this does not work with my model - maybe I have a wrong pinpout?

I am using a SONY PVM1492 video monitor, I connected three BNC cables (R/G/B) to the monitor and a 15pin SUB D Connector to the terminal according to following pinout

R_signal = 11
G_signal = 10
B_signal = 9
R_ground = 1
G_ground = 2
B_ground = 3

taken from https://www.larosse.net/pc100/VR241.html

but I get no picture.

There is remark on a jumper between pin 5 and 13 - maybe this needs to be connected? I will not try before confirmation not to fry my machine....

Maybe somebody has any experience with color on the VT240?

Regards
Stephan

 

[cjs]

Unfortunately the pinout you reference just gives descriptions like "P4 coax center in BCC17 only -- nothing in BCC03" and "P1-5 jumper" for the pins, so I have no data on what's coming out of that connector beyond the R, G and B signals you describe in your post. Do you have a description of all the signals on the connector?

Looking at your photo, I notice you have no sync signal going to the monitor. Is your source sending sync on green, and does your monitor support that? If not, you'll need to separately connect sync output of the system to the "EXT SYNC" input on the monitor, and push the "EXT SYNC" button on the front.

Note that the monitor needs composite sync, i.e., mixed hsync and vsync. If your source produces only separate hsync and vsync, you'll need to combine them. (This can be done adequately with a single XOR gate.)

 

[spiceminer]

@cjs the video monitor supports sync on green or an external sync source.
I dont have the pinout from the VT240 - the only reference I have found on the internet was the page cited above



which is from the Rainbow I suppose. Not sure if the VT240 differs. Unfortunately I cannot find the video out pinout from the VT240 schematic

 

[spiceminer]

2 minutes later.... in the pocket field service guide is a reference



Maybe I have to tie 13 - monitor present to ground to get a signal?

 

[cjs]

Right, I'd suspected that your PVM supports sync on green; it's fairly common in Sony models. And from the connector you dug up, it appears that the terminal would be doing sync on green since it appears to have no separate sync outputs, composite or otherwise.

The first step is to confirm that you're not getting sync on your RGB input by pushing the "H/V DELAY" button on the front. This will delay both sync signals a bit and add some brightness to the retrace periods so that you can see a video representation of the sync on the display. Try it first with a working composite signal so you can see what it looks like.

When you try that on the RGB input, you'll be able to confirm that you're either not getting sync or you're getting sync but a black screen.

The next step for debugging would be to wire the "Monochrome output" (pin 12) into one of your PVM composite inputs. If that's working, try that into the green input of your PVM to ensure that your RGB inputs are working and accepting sync on green.

If it's not, yes, you likely have to either ground or raise high the "Monitor present" line. Whichever way you do it, use a resistor of at least a few hundred ohms (I'd probably go for around 4700) to ensure that you're not shorting anything.

 

[Radix]

You need the link on "monitor detect" otherwise you get a "No monitor" error message displayed on the screen (!) - Rather reminiscent of "keyboard error - press F1 to continue"

You can test the monitor with the mono composite output on the BNC connector on the VT240 as well, and yes, the VT240 provides Sync on green.

I made up a cable for my VT240 and use a small Sony monitor just like you are doing...

Robin

 

[spiceminer]

Interesting, When I make the bridge between Pin 5 and 13 the "monitor error" message disappears.
But the bridge has no influence on the signal coming out from the R/G/B Pins.

Yellow is the BAS monochrome combined output from the BNC port of the VT240.
R/G/B are the seperate signals, showing the sync signal available on green (as well as on the BAS signal).

But unfortunately no signal on the SONY monitor in "RGB mode" - the BAS signal shows a signal on the monitor but only on the separate "video in" BNC socket.

 

[Radix]

The VT240 output looks fine, but there are many options on those monitors...

 

[cjs]

Yellow is the BAS monochrome combined output from the BNC port of the VT240.
R/G/B are the seperate signals, showing the sync signal available on green (as well as on the BAS signal).

But unfortunately no signal on the SONY monitor in "RGB mode" - the BAS signal shows a signal on the monitor but only on the separate "video in" BNC socket.

It really looks like your PVM is not reading sync on green. But first, have you checked the sync signal on both a known good composite input and on your RGB inputs from the VT240 by using the "H/V SHIFT" button?

Next, with the RGB cables plugged in, try plugging the monochrome output from your VT240 into the "EXT SYNC" connector on the back that's next to the RGB inputs. Make sure both RGB and "EXT SYNC" are selected on the front panel.

 

[spiceminer]

@cjs Thanks a lot, I will try! Can you please tell me what the H/V Shift button does?

 

[cjs]

Can you please tell me what the H/V Shift button does?

Sorry, it's "H/V DELAY." I always get that wrong.

As I mentioned above, the easiest way to understand it is to display a working video signal (on any input) and push the button.

What it does move the start of horizontal and vertical retrace on the monitor to before the actual waveforms in the input that signal that, so you'll see the top of the screen moved down a ways, and the left hand side of the screen moved to the right. The horizontal and vertical blanking areas also have their brightness increased, so you can actually see a visual representation of the horizontal and vertical sync on the screen. This is mainly useful just to confirm that you are getting a sync signal even if your screen is entirely black otherwise, but it can also in the odd situation help you to debug sync signals that are present but malformed in some way.

 

[cjs]

@cjs Thanks a lot, I will try! Can you please tell me what the H/V Shift button does?

Oh, I should mention, if you have difficulty using the H/V DELAY feature, or are unsure about what you're seeing, let me know here and I will set up a test image on my PVM (a Sony PVM-9045Q) and post photographs of that display and the H/V DISPLAY generated from that.

 

[spiceminer]

When I connect the BAS output (BNC connector) from the VT240 to the Green input BNC connector of the video monitor, I should get an image, right?

This is not the case for my setup. Maybe the monitor is not working correctly...

 

[cjs]

When I connect the BAS output (BNC connector) from the VT240 to the Green input BNC connector of the video monitor, I should get an image, right?
This is not the case for my setup. Maybe the monitor is not working correctly...

You should, yes. What does H/V DELAY show when you do that?

But still, that's skipping a few steps in the debugging. Try the both the monochrome and green outputs into a composite input on your PVM, and also check the H/V DELAY on those. And if you're getting a sync'd image from your monochrome output, try using that to feed the external sync, as I mentioned earlier. (And again, make sure you've pressed the EXT SYNC button when doing that. And, come to think of it, make sure you're not using external sync when you're trying to use sync on green, since that would—I hope obviously—cause the monitor to ignore any sync on green.)

This is looking enough like a potential monitor problem that you should be trying known-good signal sources on all inputs, with various combinations of external and internal sync. Remember, you can plug any signal with sync on it, even a regular video signal, into the external sync input, and use that as a sync source for any input, composite or RGB.

 

[spiceminer]

@cjs Thanks very much for your kind support, which is highly appreciated


I get a picture using the Sync+Green output of the VT connector to the composite video input of the PVM.

As already stated, the composite output from the VT is as well working when connected to the composite video input of the PVM.

 

[spiceminer]

...this is what happens when I press the H/V delay button:

when using the Composite input.

in RGB mode the picture tube remains dark, independent from all switch settings

 

[cjs]

Yup. That wide vertical bar is the horizontal blank area, and the narrow horizontal bar is the vertical blank area. You should get a similar image on the RGB input (minus the text) if you plug the composite line into the EXT SYNC input and push the EXT SYNC button. (It should be same whether a composite or the RGB input is selected.) If that works, you can then try plugging the RGB lines in, while continuing to use EXT SYNC, and you will likely see a display.

Are you absolutely certain that that PVM supports sync on green? (We know the VT240 is sending it, because you 'scoped that out above.)

 

[spiceminer]

Dear @cjs ! Thats right! Obviously, the monitor does not support SOG. I found a manual of a similar (but not exaclty my type) monitor stating SOG compatibility.

When I just put the composite output into the ext sync input of the monitor, I get a picture!

So, I just need to put some color on the screen to verify

 

[Radix]

If you go to display setup and selet colour or colour+mono, you should get this:

 

[spiceminer]

Or you can invoke the color bar test as describes in the programmers manual in VT100/local mode