Same problem on Mac OSX and Windows. Have an external
chassis for hard drives with standard power connectors.
An adaptor connects the IDE pins to USB (tested).

When I put the 40GB disk in my old Dell Poweredge (Debian) it recognizes it fine. When I put it in the external drive chassis it is not recognised via usb adaptor by either Mac or Windows. The power supply is working fine, I've tested the 5v and 12v pins on the connector. Strangely the drive is very quiet when powered on.

Any ideas? Disk is a Western Digital WD400BB-75FRA0. Have tried varying jumpers also to no avail.

Clarly I'm missing something, apologies if this is too easy but you guys always sort me out!

Then the IDE to USB adaptor does not work.

Yeah, it looks like your USB adaptor/enclosure filters out some commands (in your case to activate/spin up the HDD) or just does not support the instructions set of your HDD (can happen when using old enclosures with new HDDs).

AND/OR, a more remote possibility is that your HDD needs the "special" commands that are used to do a staggered spin-up of multiple HDDs in an enclosure (to avoid e.g. that 100 HDs try to start all at once, therefore causing a power surge), which is provided only by special BIOSes or the OSs.

1 members found this post helpful.

Thanks guys but I've tested the IDE to USB by putting the drive in a Mac and connecting the IDE to the Mac USB with the adapter, - works fine.

The problem is definitely in the external unit power supply. I cannot understand why it shows the right voltages but nowt seems to reach the drive.

How and where are you measuring the voltages? May also be that the power supply voltage goes out of spec under load but reads good under your test conditions. When the voltage is low to the drive you usually get a repetetive clicking from the drive as the actuator continuously tries to repark itself to its home position. If you hear nothing out of the unit, it may indicate a break somewhere in the circuit i.e. no power is getting to the hard drive.

1 members found this post helpful.

I take it you are Kilgore Trout the (In)famous science fiction writer? I am a great fan of your literature, - especially the ones with pictures!

On the subject of the hard drive, there has been a major advance. The power supply has two connectors "daisy chained", ie two plugs on effectively one cable, one at the end, one in the middle.

When I connect the hard drive alone, - nothing, but when I connect another device to the second power connector, lo and behold both drives spring to life!

You seem to have a good idea about the various processes in power supply connections, - any idea what this indicates?

Really appreciate yr help, - and your marvelous literary abilities!

ML