commodore 1084 monitor

[phreak97]

i have a PAL commodore 1084 monitor, it has scart.
with my amiga, it works fine, but i made up a cable to convert d-sub to scart, and when i connect up the sync line, h-sync is ok, v-sync is out, and it loses a fair bit of colour, if i disconnect the sync line, obviously sync goes all over the place, but colour is good.

so what the hell:/

[viletim]

Your commodore monitor, or any TV/monitor with a SCART input for that matter, don't accept TTL level composite sync. Instead they strip the sync signals off the composite video that often accompanies the RGB video. If you want to feed the monitor TTL sync then feed it into the video input with a 1k resistor in series.

ps. it's not possible to adjust the colour level on an RGB monitor so how do you 'loose colour'? and what's d-sub?

[NFG]

1. There's not much chance he's using a TTL sync signal.  Consoles output analogue sync along with their analogue RGB.

2. a d-sub connector is the delta-shaped connector you find on serial, parallel, and VGA connectors, neo, sega and atari controllers, and a billion other devices.

[atom]

Try a pot on the line with the problem. Worked well for me on my Apple monitor.

[phreak97]

a pot wont bring the color up, itll just reduce it, but thats not the problem anyway, i believe if i fix what's wrong with the sync, ill fix everything.. this is because when i disconnect the whacked sync, the color works. it's like the sync signal is doing something really bad to the whole process.. but i dont see how, since it works fine on a dsub monitor..

what i'm attempting is to make a converter to plug all my dsub cables into scart..  

[Guest_viletim]

phreak97,
which game console are you trying to connect your monitor to?

The fact that you refer to a 'sync' signal makes me think you're doing something wrong. To connect your console to the 1084's SCART input you should use: red, green, blue, composite video, ground.

[Endymion]

Why would it like composite video, but hate composite sync though? This seems to make little sense to me. It's been several years since I have fiddled with my (NTSC non-SCART) Commodore 1084 but I could swear I remember using sync and not video, I sure seem to remember reading diagrams that specified that too.

[NFG]

It should be noted that, from what I've heard, PAL 1084s use composite video, but NTSC units use only composite sync.  I know for sure both my NTSC 1084s refused to use composite video.

[Guest_viletim]

Endymion,
because the SCART (on a 1084 or anything) standard says 'thou must use composite video' :)

actually...the sync part of a composite video signal has an amplitude of 0.3Vpp, if you connect a TTL composite sync signal (3-5Vpp, assuming it can drive a 75 ohm load) you are very much overloading the input. It won't damage anything but it might make the monitor act strange.

Lawrence,
yes, that seems to be the case, authough i've got a PAL AU 1084S with a 6 pin DIN socket labled 'lin. RGB'. Is that what you normaly find on an NTSC model?

[NFG]

the NTSC 1084 has no SCART socket, and instead has (depending on the model) 2 DIN sockets, one for analogue and one for digital (lin.) RGB.  The other model has only (IIRC, it's been half a decade...) a DB9 socket with a switch.  Or a DB9 + DIN.  I forget.  No SCART tho, of that I'm sure.

[phreak97]

Guest_viletim i have a pal 1084S which i am using mostly, but i'd like to be able to use the 1084 too..

if i pulled the amplitude of the sync signal down to 0.3v can i expect it to work? i might put a variable resistor on it sometime and see what turning it up and down does.

while it may work with composite video, im making a dsub converter, so i dont really have composite video available.

i thought my 1084S didnt work with composite video, because it definately didnt with a psx i have here.. but when making a test cable for my saturn(s), i HAD to use composite video.. the composite sync pin did next to nothing. so i have come to the conclusion that i dont know wtf.. i need to make up an alligator clip to dsub cable and some other crap so i can do tests without resoldering the cable every time

[Guest_viletim]

if i pulled the amplitude of the sync signal down to 0.3v can i expect it to work? i might put a variable resistor on it sometime and see what turning it up and down does.

as i said before, a 1k resistor in series is the traditional way to do it. It forms a potiential divider with the 75 ohm termination resistor inside the monitor.

i thought my 1084S didnt work with composite video...

I doubt it does too. SCART input = composite video, other input (dsub, din8, etc) = composite sync.

[phreak97]

it's strange though, cos im using composite from my saturn..

[phreak97]

1k almost got hsync working.. vsync is still out, and i found out the color problem is only with my sms2. i tried a pot, but the screen for some reason goes black before it syncs properly..i dont get it.. should i have a cap on the line?

[phreak97]

after playing around with the cap and a pot, i found it synced perfectly if i turned the pot to 0 so i took the pot out and it works fine.. all it needed was a 220uF cap

i havnt tested the sms2 yet though, ill do that tomorrow.. i got it working on a megadrive.

[atom]

I was talking about a pot on the sync but whatever looks like you got it.

[phreak97]

atom, this IS on the sync.. i know it's retarded cos the 220uF caps are normally for the video signals.. but it seems to have worked anyway. theres a single line of pixils at the top and bottom of the screen which is a bit broke, like the one at the top is stuffed ad the one at the bottom is what the one at the top should be. it honestly doesnt bother me at all.. but if this is cos i used the wrong cap, what value should i be using?. though it's quite possibly just my megadrive.

[phreak97]

I tested it on my SMS2, sync works fine, but the darkness and the horizontal blurring is still there. funny thing is though, it doesnt start off there, at the sega logo, it's perfect colour for half a second, then fades to ass. this leads me to believe I should be blaming a capacitor for the problem, but what capacitor? could this be just that i am using the wrong value on the sync line? cos i have no idea what value i should be using.

[Guest_viletim]

phreak97,
see http://members.optusnet.com.au/eviltim/gam...t/gamescart.htm

[phreak97]

Guest_viletim, read up.. im making a dsub to scart converter, so i need it to work with composite sync, not composite video.. but i need to know what value cap and maybe resistor to put on the sync line

[Aidan]

DC offset. That's what the capacitors block. It means that the sync output is superimposed on top of a existing DC voltage, probably above 0.3V. The monitor is just looking for the sync pulses, so the DC voltage is confusing it. The capacitors block the DC voltage, so that only AC waveforms pass through (like the sync for example).

[phreak97]

yeah, i got that much.. but im still getting problems, i think i might have the wrong value cap, how would i know what value to use? the 220uF works fine with my megadrive, but it only works for half a second on my sms. it's still syncing, but getting really crapped up color

[Yod@]

Not sure if it's pertinent to your problem, but I had sync issues with a couple of my monitors a while ago (one Amstrad monitor which I hacked a SCART socket into, the other a 14" arcade monitor for my cocktail cabinet).

IIRC (it was a long time ago ) the sync on my Amstrad used to be ok when it was first powered on, but would then slowly start to drift off (it would take a different length of time depending on which console was connected). I think I solved it by putting a resistor across the composite video input and ground - I'd have to open up the monitor  and look again though.

With the arcade monitor, I thought I had it all sorted until I connected up my Dreamcast one day - whenever there were any bright scenes (explosions or whatever) the arcade monitor would lose vertical sync and the picture would roll.
Again, a resistor tied across the composite video/sync input and ground solved it.

[viletim]

phreak97,

Yup, you're right, it seems these sync signals have very little drive ability. Here's (attached) a definitive answer. This one's guaranteed to work :)


PS. crap colour is likely being caused by missing components on the video lines. That's why I posted a link to my page.

[phreak97]

yeah, that would work, if dsub had a 5v output.

i believe i can make this work with just components on the line.
i already do have those components on the sms rgb, it works fine on my other monitor

[Guest_viletim]

yeah, that would work, if dsub had a 5v output.

This sub-miniture D connection system of yours seems to be a complete failure. No composite video, no power source....

i believe i can make this work with just components on the line.

well...obviously you can't, as you yourself have proved. The problem is lack of drive from the console. Adding components in series to the signal will only attenuate the signal even further.

Your only hope now is to remove the monitor's termination resistor. I don't recommend that though...it's just asking for more 'fun' surprises.

[phreak97]

however, it works fine with other consoles. im going to try a couple more things before i give up. the monitor is syncing quite happily, it's just the colour is screwed. and it is not caused by the colour signals.
i am not making any new dsub pinout, i am using the same pinout that was used for the pal commodore 1084S monitor. it is not my fault it lacks anything remotely useful. all the pins that arent used by the consoles have other functions, so i cant go adding my own stuff, itll mess with the monitor.

[phreak97]

HA! never tell phreak97 he is wrong without proof of it!
i changed the cap to a 100uF one cos that's what was recommended for some dude using an arcade monitor, so i figured, what's the harm. it made no difference whatsoever. i left it in anyway cos it seems to do the same as the 220. i then put a pot on the line. the monitor synced and looked ok when i turned it all the way down. however it was a 100k pot and had a minimum value that jumped all over the place on my multimeter. so i got a 10k pot which is still a little overkill, but i managed to work out it synced with a good picture at about 144 ohms, i stuck in a 150, also what was recommended for the other dude, and it works:)

if it doesnt work with another console cos of that, ill put in a switch to bypass the resistor.