To: Alex Freed Alex Freed wrote:
Polymorph wrote:Alex, I'm just curious how you arrived at 51 Ohms. Was it through trial and error, or some other means of deduction?"51" looks very precise - it's just a standard value I tried when 75 proved not to be low enough. I used a scope to see what the signal looks like. I would not use a much lower value for fear of overloading the GS's output driver, but 51 is safe.
OK, so when I next go to the electronics store, I might pick up a 51 Ohm resistor in addition to the 200 Ohm pot. As we're only talking a few cents extra. Actually, it's rather embarrassing walking into an electronics store and walking out with a 38 cent part. When I was confronted with this problem the other day, I actually stood in the store until I thought of something else I needed for a different project just so that I didn't have to look the dealer in the eye when he said "that'll be 38 cents please". ;-)
When you wired up the 51 Ohm resistor, I assume it was in the same manner as I tried with a 75 Ohm resistor - i.e. the resistor between the composite sync and ground?Yes.
I thought that's what you meant.
Could you do me a favour and measure what the voltage is between composite sync and ground? It could be that I haven't lowered my composite sync signal quite enough? Maybe the sync level is 0.3V P-P. I think this is what is listed for one of the other 1084 inputs. Perhaps this is an omission from the specs of the RGB port?I don't have this system connected at this time, sorry. However using the 200 ohm pot as was suggested here should do the trick for you.
No worries. Its good to hear of someone who experienced a similar problem as myself using the 1084S with the IIgs. I wonder why most people don't have a problem? Did later revisions of the 1084 line come with greater tolerance to sync levels? It has me stumped how come some 1084 monitors require modification of the sync signal and others don't.
Thanks for letting me know your experiences in using the 1084 with the IIgs, as it's almost made it a 100% sure thing for success (once I twiddle the signal a little more).
Cheers, Mike --- Synchronet 3.14a-Win32 NewsLink 1.85 A2Central.com - Your total source for Apple II computing.