The Atari ST lives!
Well, at least with the three mods disabled or in non active states...
First I connected up the existing floppy drive, switched on and with a disk in, got a normal desktop. Good!
So on with the testing....
So the first thing to try is a HD capable floppy drive.
But the Atari is not happy
, keeps attempting to read the nice new HD floppy but boots into desktop without reading the disk
Strange, I know this floppy reads double density disks without problems and it is a HD floppy drive...
Okay, so what voltage am I getting on pin 2 of the floppy IDC connector. Bugger, can't get to it
. So next best thing, get to the HDD0 pin on the HD FDD board
. Damm, I'm getting 0V
So off with it's head, sorry case (in this case the bottom section).
Oh look, a unconnected pin 2. Explains why no voltage
. But look here, a "pad" that can be soldered across. Best check that the feed from the chip does actually produce a high logic level (5V or thereabouts) with a HD floppy in the drive. Testing with a meter confirms this
, so power down and out with the soldering iron and hey presto, a logic high feed on pin 2 of the IDC connector
. When measured on the HDD0 pin on the HD FDD board I get 3.49V. Okay, a little lower than I would have liked, but still (as far as TTL logic chips are concerned) a logic high. BUT
I later found out that this part of the floppy drive circuit is a HD disk select INPUT
not an output
as it does not change to a low level when there is a DD disk in the drive, nor when there is no disk in the drive!
To get the HD output signal, solder a wire from "SW3" "HD IN" switch (the pin next to the "SW3" marking) to pin 2 of the floppy connector (switch "SW3" is in the bottom right of this picture, better picture coming soon!). To enable the Atari to sense when a disk is changed you also have to solder a wire across the two pins of "SW2" "CT IN" (top right of picture).
In goes the HD floppy, reset the Atari and the friendly sound of an Atari booting from floppy is the result
And bonus, the Atari boots the Lascan driver (slight thought of panic as I see strange coloured lines on the screen before my memory kicks in again- phew!)Whoo-hoo!! It works
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