CGA computer monitor

[Mikeley]

Hi,

Anyone remember CGA? I havent seen one in years. This is an industrial CRT monitor with some problems. Model is Lucius & Baer CC14VAO-CH.

It came to me dead. After replacing many electrolytic caps, it came back to life. I generally check capacitance and ESR on all once I find a few suspect.
Probably more trouble than it's worth, but I like old stuff. This monitor requires a H-sync signal before it will run.

The only CGA source I have is a BK Percision 1275. I made up a connection from a serial cable and built a 'gender adaptor' to sort out male/female issue at the monitor. Now, this could be the issue!

In the attached pictures, on solid primary colours, and white, there is a solid wide vertical bar down the screen. This can be moved across the screen with H-Pos pot at the rear of the monitor. On other test patterns, vertical lines look split, and on the color test, RGB looks just a bit odd as in the attached image.

I'm not an expert on monitors, so would appreciate your help. See attached pictures. Any opinions, checks, what should I expect?

Have an basic tools, oscilliscope, DVM etc. and willing to learn more!

M

[kc8adu]

Re: CGA computer monitor

not cga.maybe ega or vga.possible nonstandard scan rate.
the image shows its set to the wrong scan rate.
edit.
its a vga.
i remember fixing one a while back.was in a husky plastic molding machine.

[Wizard]

Re: CGA computer monitor

Your interlace is off, need to find more small value capacitors around the IC that takes inputs and outputs horizontal and vertical pulses.

CGA is TV chassis type without tuner, video is fed in either by composite or TTL. The timing is same as TV.

15.7Khz 60Hz. Plucked from wiki on CGA:

"Type Digital, TTL
Resolution 640h x 200v, 320h x 200v
H-freq 15.75 kHz
V-freq 60 Hz
Colors 16"

Cheers, Wizard

[kc8adu]

Re: CGA computer monitor

its probably ok if he treats it as vga.

Your interlace is off, need to find more small value capacitors around the IC that takes inputs and outputs horizontal and vertical pulses.

CGA is TV chassis type without tuner, video is fed in either by composite or TTL. The timing is same as TV.

15.7Khz 60Hz. Plucked from wiki on CGA:

"Type Digital, TTL
Resolution 640h x 200v, 320h x 200v
H-freq 15.75 kHz
V-freq 60 Hz
Colors 16"

Cheers, Wizard

[Mikeley]

Re: CGA computer monitor

Yes, confirmed the H-sync at 15.76Hz, and V sync at 60.1Hz. The CGA system is based upon TTL level signals. This is smilar to EGA with the intensity pin 6 providing additional colors. It's a TV without a tuner! It's not possible to treat this as a VGA input signal.

H and V signals go trough an XOR arrangement and then on through a 74LS123 'one shot'. From there a NPN transistor provides drive, possible level shift. Will have to explore the board some more to understand the circuit. It's a real pain to access!
There is an analog multiplexer (4051BE) in there also. Not sure why. Guessing this could be a switch depending on scan rates?

I did try to vary H-hold pot on the PCB, to get a lock on the images I attached. I also tried EGA source from the BK1275 but could not get a lock. Measured H-freq at 21.82kHz and V-freq at 59.6Hz. Checked on a scope etc.

From your experience, is this issue more likely to be H-sync related? Will be checking Vertical and Horizontal deflection IC specs.

[Wizard]

Re: CGA computer monitor

Yes!! Horizontal is way off. Should be 15.7KHz.

Where is 22KHz pulses coming from while inputting 15.7KHz H and 60Hz V? That's your hint, trace back.

PS: EGA wiki:

"Type Digital, TTL
Resolution H x V 640 x 350 other modes available
H-freq 15.7 or 21.8 kHz
V-freq 60 Hz
Colors 6-bit (64)"

Cheers, Wizard

[kc8adu]

Re: CGA computer monitor

again its vga not cga!
try 31.5 h

[Wizard]

Re: CGA computer monitor

You got me stumped! 1 second google confirmed that.

Yes, go old fashioned VGA timing. Unusual to use 9 pin plug on a VGA.

Cheers, Wizard

[kc8adu]

Re: CGA computer monitor

all sorts of nonstandard connectors on industrial stuff.
i have about 30 custom cables i made just to test/service oddball monitors.got an allen-bradley on the bench right now.oem panasonic but custom cable needed to service it.made one 15+ years ago.

[Mikeley]

Re: CGA computer monitor

This thing has a hex buffer behind the 9 pin d-type input at the rear... it only accepts TTL level logic. The pin out matches with CGA and EGA standards which both have lower sync frequencies.

You have a point though, I also have seen some wierd industrial stuff. Just need to figure out how to get 31.5kHz into it?

[Mikeley]

Re: CGA computer monitor

again its vga not cga!
try 31.5 h

Monitor all ran fine when returned to owner. The H-sync was 31.4-31.5KHz. Monitors such as these do not conform to CGA/EGA standards, in this case, recapping and the occasional faulty power supply seem to be the only issues. The TTL levels, and pin outs match these standards but timing is everything!

[Scenic]

Re: CGA computer monitor

Yes, go old fashioned VGA timing. Unusual to use 9 pin plug on a VGA

Old Eizo CRT monitors used this. i remember having an old (early 90s?) FlexScan 5070S or something (16" IIRC) which was a VGA monitor, but had a 9pin socket at the back (+ BNC connectors).
it worked but developed serious issues with the picture becoming wobbly/trembling sideways till you moved the picture to one side a bit with the front controls. then it stopped for a while (an hour or so). ended up parting with it and buying a much newer Eizo F520 17" CRT. was just too annoying to play around with the settings till the pic stopped shaking all over the place..

i still have the original adapter and cable that came with it somewhere. 9pin cable (2x male .. i think it was wired up 1:1) and the adapter was 9pin (female) to 15pin (male).

edit: found the adapter. tried opening it up to see how it's wired up, but one of the screws is covered in something .. seems like glue.. destroyed the screwhead trying to get it out.. damnit.
i guess i have to cut a slit in the head with my dremel some day..

[HMTR]

Re: CGA computer monitor

Hate to bump an old thread, but how did you come up with the pinout for the 9 pin on the back of this unit? I've been looking everywhere for this.

Thanks!

[mtorr]

Re: CGA computer monitor

I hadn't had any luck with trying to fix our old CRT CC14V, I ended up just making a cable that ended up being a 15 pin to a 9pin.

[niko]

Re: CGA computer monitor

Please help me find a diagram of the electrical monitor Lucius & Bar CC14VAO-CH or converter circuit CGA-VGA.