Help! Problems connecting 3.5" HD to Viper520

[mr_a500]

I've been attempting to connect a 3.5" harddrive to my Viper520. I already have a 2.5" HD connected. I'm using a junked crap PC power supply to power the 3.5" drive and have the 3.5" drive cable correctly connected to the Viper. I also have master/slave jumpers set.

The problem:
As soon as I turn on my Amiga, the PC power supply switches off - meaning no power to the 3.5" drive. When I turn off the Amiga, the PC power supply works again. The same thing happens when attempting to connect a CD-ROM. WTF? Any ideas?

[Argus]

What kind of power supply are you using?  I've heard that ATX supplies need a signal from the pc motherboard to switch on/off.  Try another (older) AT style p/s and it will probably work okay.  I've used older AT supplies to run external cdroms, etc. w/o problem.  btw, I wish the Viper/Mtec520 was still available.

[mr_a500]

Yes, I thought it must be something like that - signal from PC motherboard. Is there any way to disable that? (I don't want to have to search around for old power supplies - or pay for them. This was just for a quick emergency backup.)

Quote:
"btw, I wish the Viper/Mtec520 was still available"

He, he :-D I found mine in Australia a couple years ago brand new. I got the last one. I think the reason they still had it was that they didn't mention "Viper520" anywhere in the advertisement. (they're out of business now)

[Argus]

I don't know if you can disable the power switch.  It is probably an IC on the p/s motherboard.  You might try opening it up and see if there is a jumper or something to make it AT-compatible.  I've seen supplies with both AT and ATX connectors so maybe... But be very careful, the capacitors, etc. will have plenty of juice left in them if you just recently ran it (I zapped myself before on an old Atari ST p/s that had been unplugged for a week).  If the p/s switch can't be disabled, I'd try a local computer recycler for an AT supply.  Too bad I just threw out three AT supplies a month ago.