• Please review our updated Terms and Rules here

Macintosh LC to VGA adaptor settings

H

habibrobert

Member
Joined
Dec 18, 2012
Messages
39
Location
Florida
Hello everyone,

I am trying to get a Macintosh LC to work with a VGA LCD monitor. I went out and got a DB15 to VGA adaptor, but I cannot figure out what the 10 correct pin setting is on the device? The monitor keeps on saying "incompatible signal". I have here a copy of the pin settings, I was wondering if anyone would be kind enough to tell me the correct setting to try on here? I'm rather new at all of this and would really appreciate some help. I've been reading on the forums that the proper setting should be for a 12 inch RGB monitor, is this correct?

Many Thanks.
 

Attachments

  • Screen Shot 2012-12-18 at 3.01.38 AM.jpg
    Screen Shot 2012-12-18 at 3.01.38 AM.jpg
    24 KB · Views: 18
Try the setting for 13" RGB. Modern monitors don't tend to get along well with the 512x384 signal, I assume the sync rate must be too low. You may even be able to use the 16" color setting, though I don't know for sure if the original LC supports it.
 
Set the adapter to VGA/SVGA, then fiddle with the sync switches until it works. Macs can have differing sync types and pinouts depending on the model. Mode 5 (seperate H and V sync) is likely the setting you need on a modern LCD as some won't take composite sync.
 
Well, it also depends on the video source. If his card can't output 60Hz, or, if his LCD doesn't support higher refresh rates, he may be out of luck no matter what adapter he uses.
 
Hi everyone, thanks for all of your help!

I tried the vga/svga setting on mode 5, now this is progress, the monitor does not bring up a "cannot read input signal", instead i can see the back lighting turns on, yet the screen is black. Does anyone know what this means? None of the other settings got me this far on vga/svga, no monitor sand "cannot read input signal" on all the other modes. Any possibility to get this guy to wo

Many thanks
 
Here is a picture of mine with correct settings

Here is a picture of mine with correct settings

Not sure if this is the same vga convertor but here is a picture of mine with the settings.

This was used on a mac LC475 to a vga 15 pin monitor. Rez was 1280x1024 i think


db15 settings to vga.jpg


habibrobert said:
Hello everyone,

I am trying to get a Macintosh LC to work with a VGA LCD monitor. I went out and got a DB15 to VGA adaptor, but I cannot figure out what the 10 correct pin setting is on the device? The monitor keeps on saying "incompatible signal". I have here a copy of the pin settings, I was wondering if anyone would be kind enough to tell me the correct setting to try on here? I'm rather new at all of this and would really appreciate some help. I've been reading on the forums that the proper setting should be for a 12 inch RGB monitor, is this correct?

Many Thanks.
Click to expand...
 
Hey digress,

Thanks for the pictures, I used your settings, and the same thing happened. The monitor could detect the signal, but the screen was black. When I turned off the computer, I could even see the screen get a little dimmer because there was no signal going to it. So I know something is happening. Does anyone know what this could mean? Thanks for the help!
 
The LC video interface includes three "Sense" pins (4,7,10) that tell the LC the identity of the monitor. These pins must be grounded in appropriate combination for specific monitors. Standard VGA monitors may not do this the way Apple's own monitors did it, so you may need to tie the correct pins to ground at the adapter. Look online for "Developer Notes" for the LC, page 17 for specifics.

I tried a ten-switch adapter like the one you have, but it was hard-wired with inappropriate ID sense signals for my IIsi, so would not work regardless of correct synch and RGB switching. I reckon to make my own adapter.

Also possible that you have a failure in the ground signals for R/G/B? Could be that the the synch is recognised, but the R/G/B not? This would not be in the monitor or cable, which ties all grounds together. Not sure what your adapter does with ground signals - worth probing with a multimeter to see all grounds are passing through, and non-ground signals are not shorting to ground.


Rick
 
The instructions look just like the ones for mine. Try setting 2367. I'm using this with an LC III and an older IBM VGA monitor. This is VGA with mode 5.
 
Yes, there is a start up chime, at least most of the time there is.... which makes me think the hard drive might be starting to fail? I'm not sure. But for the most part I do hear a chime. That is a good sign...right?

tomasont, thanks for your setting, I tried that but had no luck. The monitor did detect a signal and the backlighting did turn on, but there was just a blank screen! I am using an LCD monitor, I'm wondering if that could be the problem? I'm not sure what exactly the refresh rate on my monitor is... I tried looking for a manual online, but had no luck. Does anyone else have any other suggestions? I may look into making an adaptor for this myself... do you think this may solve the problem?

Thanks for all of the help!
 
habibrobert said:
Yes, there is a start up chime, at least most of the time there is.... which makes me think the hard drive might be starting to fail? I'm not sure. But for the most part I do hear a chime. That is a good sign...right?
Click to expand...

The startup chime is your indication that the motherboard (CPU, RAM, ROM) is working. It has no relation to whether or not any hard or floppy drives are working. A Mac will give the startup chime even with no drives connected at all.
 
A PRAM zap sometimes solves weird video problems. Turn on the machine and hold down Command-Option-P-R until you hear the startup chime again. Some say to hold it down until you hear it three times.
 
Screen Black but a chime

Screen Black but a chime

Mine (LC 475) is a direct descendant of your system.

I got the black screen with no graphics but a chime. Turns out they cmos battery on the motherboard was dead and needed to be replaced. The system will not boot or show video unless you do. It's like a lithium battery, abou $10 and radioshack. I had it happen a couple of times while I really need to complete a project.

Check this anyways.





habibrobert said:
Hey digress,

Thanks for the pictures, I used your settings, and the same thing happened. The monitor could detect the signal, but the screen was black. When I turned off the computer, I could even see the screen get a little dimmer because there was no signal going to it. So I know something is happening. Does anyone know what this could mean? Thanks for the help!
Click to expand...
 
I don't think the LC should have any problem booting without a battery. The only Macs I have that are finicky in that way are 68040 machines... all my older ones (including an LCIII) have no ill effects from it other than the clock being wrong.

But if you want to be sure, there is a method you can try, which doesn't require buying a new battery... just turn the machine on, wait for the chime, then quickly flick the power switch off and back on again. If it is a problem with the video not initializing properly like in the LC475, then that trick should be enough to kick start it into showing a picture. Note that it is not good for the hardware to do that... I'd recommend unplugging the hard drive before trying it, and even then you really shouldn't do it more than once. But once should be enough to tell you whether that's the problem or not.

And BTW, if it turns out that you do need a PRAM battery, don't pay $10 for one... you can get generic ones off eBay for around $3 each, and they work just fine.
 
Old Thrashbarg said:
I don't think the LC should have any problem booting without a battery. The only Macs I have that are finicky in that way are 68040 machines... all my older ones (including an LCIII) have no ill effects from it other than the clock being wrong.
Click to expand...

I have the original LC and it boots up just fine with no battery installed.
 
On an LC you are probably going to want to set the resolution to 640x480 at 67Hz instead of 60Hz. I'm pretty sure this is what I had to do on my IIsi and LCIII to get video to display.

You mentioned the black screen after hearing the boot chime... how long have you let it sit before restarting? I ask because I've had a few times where I've turned a vintage Mac on and it takes a couple minutes before any video is displayed. Once I was impatient and thought my system wasn't working either but apparently I wasn't waiting long enough.
 
habibrobert said:
tomasont, thanks for your setting, I tried that but had no luck. The monitor did detect a signal and the backlighting did turn on, but there was just a blank screen! I am using an LCD monitor, I'm wondering if that could be the problem? I'm not sure what exactly the refresh rate on my monitor is... I tried looking for a manual online, but had no luck.
Click to expand...

That setting should be 640x480 at 60Hz. That's a very basic VGA setting. I would think any LCD monitor should handle that. Have you tried the LCD monitor on a PC? That would test the cable and the monitor. Or do you have a CRT VGA monitor that you could try? Just keep eliminating possible issues.
 
You must log in or register to reply here.
Back
Top