harald@ccicpg.UUCP ( Harald Milne) (11/13/87)
This is not a "flame"
It's just a question
I just got the monitor. I hooked it up. Thanks to some kind soul, on
the net, I found out why it would fail.
This doesn't look nice. For some reason, this monitor hangs the A500
(from other user reports) and my A2000. For some reason, the H-SYNC needs to
be buffered through a TTL driver. (like a 74F00).
The symptoms of this failure:
1) The machine won't boot.
2) If you leave the connector off, the machine will boot,
reconnect the monitor, after boot, all is fine.
When the machine "hangs", I believe it hangs in the "Fat" Agnus
test. (Color codes). What's really funny about this, is the Amiga only hangs
during "testing of hardware" type of operation. Like warm boot. (Or cold)
Can anybody shed light on this? CBM? CATS?
Is this monitor a piece of execrement?
--
Work: Computer Consoles Inc. (CCI), Advanced Development Group (ADG)
Irvine, CA (RISCy business! Home of the CCI POWER 6/32)
UUCP: uunet!ccicpg!haraldgrr@cbmvax.UUCP (George Robbins) (11/14/87)
In article <4817@ccicpg.UUCP> harald@ccicpg.UUCP ( Harald Milne) writes: > > This is not a "flame" It's just a question > > I just got the monitor. I hooked it up. Thanks to some kind soul, on > the net, I found out why it would fail. > > This doesn't look nice. For some reason, this monitor hangs the A500 > (from other user reports) and my A2000. For some reason, the H-SYNC needs to > be buffered through a TTL driver. (like a 74F00). > > The symptoms of this failure: > > 1) The machine won't boot. > 2) If you leave the connector off, the machine will boot, > reconnect the monitor, after boot, all is fine. > > When the machine "hangs", I believe it hangs in the "Fat" Agnus > test. (Color codes). What's really funny about this, is the Amiga only hangs > during "testing of hardware" type of operation. Like warm boot. (Or cold) Not to worry, this is a very common problem when people try to use some third party monitors. The seperate HSYNC and VSYNC signals on the video connector are not buffered, bucause they are used as I/O pins when you are in genlock mode. The CSYNC or composite sync pin is buffered and can be used without any difficulties. Most fancy monitors that have separate sync inputs, but don't have something labeled composite sync will work if you run the composite sync into the horizontal sync input. If you want to use separate sync signals, first check that there isn't some kind of terminator switch on the sync inputs that is putting them in "Lo-Z" mode - most undesirable. Second, you probably don't need a TTL buffer, a 47-470 Ohm series resistor secreted in the connector shell seems to usually unload the sync output enough that Agnus can work, and still gets enough sync to the monitor. You may have to play around with the value some, try 220 Ohm first. A few monitors act really goofy when fed with a TTL/CMOS level composite sync. Generally a 220-470 ohm series resistor will reduce the voltage swing at the monitor enough to make everything sweet. The only thing standard about monitors seems to be that they have screens 8-( -- George Robbins - now working for, uucp: {ihnp4|rutgers|allegra}!cbmvax!grr but no way officially representing arpa: out to lunch... Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)