exxos's Atari, Amiga & retro forum

Hi there.
Since a month or so I have connected my STe via the well known HD9800 v5 board for the Low/Medium Rez. Via another cable I have the High resolution. I use a 4 port RGB switch to choose among the two ST inputs and 2 ports for the TT030 where I can choose for the internal VGA and the output from the CrazyDotsII graphic card. All went well till I came across an old wacom tablet with a serial db9 plug and quickly googled for available drivers for the ST/TT. Meanwhile I stupidly connected the tablet to the second Joystickport. Started the STe up and right away I have a yellow background instead of white. In both High Rez and Low/Medium. Seems one of the RGB channels giving no signal? Is this possible by connecting a analog serial device to the joystick port. For the rest everything works, only yellow where you see white normally.
Let me be clear that it's not a monitor issue since the TT does not show this behaviour, also the MiniMac connected through the DVI is ok.
Hope anyone can shed some light on this.
Greetings from Holland.

What happens on the RF port on a TV ?

No RF on this STe ...

After investigation it seems to be the RGB switch. Strange that the TT030 does not suffer the same. It's on the same switch. Can it be that I have no resistors on the RGB lines and also not on the Mono line. In several cable guides I see this implemented. Maybe the current is to high for the switch? Then It would have presented this much earlier I would think. No problems for a month or so.

Maybe the switch isn't doing proper isolation ?

Thanks, I will check the internals. It's an electronic switcher. Ports 1 and 2 work properly on the ST where the TT was connected. Did not yet check if the TT does the same on ports 3 or 4. Will report later.

Weird stuff, changed ST to ports 1&2 and the TT to 3&4. All is well. Super strange that I had another RGB kvm 4 port switch, a Starview SV401. It did exactly the same. Yellow on 2 of the 4 ports and OK on the others (no numbers on this one, also no power needed) Could not switch when connected to the HD9800 so went back to the INline 4p switch and connected it like in the first sentence.
Sorry, a lot of nothing. Hope the yellow will stay away.

Does it yellow with just the ST plugged into any port ? (not having the TT plugged in on any connector)

TT and ST were connected from when I start to use the switch. No Yellow the first weeks. It coincided when I connected a wacom tablet to right db9 port under the keyboard. Must be a coincidence because at the end nothing seems wrong.
So no, with or without the TT connected it has this behaviour. I'm not THAT well on electronics to do measurements and know what the figures mean. When it comes back I will investigate further. Thanks anyway for the support.