Mac monitor to VGA adapter - sync settings?

[bigmessowires]

I'm trying to connect a PowerMac 8500 to a modern VGA monitor, using one of those DB-15 to HD-15 adapters from eBay that's got DIP switches to configure the sync settings. But I can't seem to figure out what settings I need - no matter what I try, my VGA monitor just ignores the Mac and goes to sleep. No errors about sync out of range, or weird corrupted video, or other things I might expect to see with the wrong DIP settings.

Here's the chart that came with this adapter:



Anyone else have this same adapter? Do the sync settings (modes 1-6) refer to the sync method used by the Mac, or by the VGA monitor? I'm pretty sure VGA has separate HSYNC and VSYNC signals, but what about the Mac?

 

[Trash80toHP_Mini]

Does it look like any of these? Video Adapter Docs Scan Dump

Which resolutions are you trying to set?

 

[bigmessowires]

It is the one posted by tecneeq in the 6th post of that thread. But my problem isn't lack of docs, it's not being able to understand the docs. I've tried all 6 mode settings for 640x480, 1024x768, and "multiple scan 21" without getting anything on the monitor.

I'm beginning to suspect the PowerMac is toast. It was working when I last ran it about a year ago, but I'm noticing there is no startup chime, and the HD spins up but I don't hear any HD activity after that. So maybe there's a hardware problem - but shouldn't I at least see a Sad Mac or something? What kind of hardware problem might cause no chime, no video, no anything?

 

[bigmessowires]

Looks like the problem was a dead PRAM battery. I removed the battery, and left the battery holder empty since I didn't have any spares. After that I started getting the startup chime again. After more experimentation with the video adapter, it seems that Mode 5 (separate sync) works. Booting OS9 now!

 

[Trash80toHP_Mini]

Excellent news. Some of the adapters have counter-intuitive setting instructions. Yours looked pretty clear, but it doesn't hurt to have someone with the same adapter try it on a like machine.