I've ran into a weird problem with a Mega ST. Maybe someone who still
reads this group may have seen something similar or knows more about
the mega chips.

Upon boot up the internal drive will not read any disk (even a blank
format).
The desktop will come up on screen and I can change resolutions.
However if I attach a 2nd Disk Drive, the Mega ST seems to try to format the
drive(disk).

I can try to access the internal drive from the desktop, when doing so,
the drive sounds like there is no disk in the drive to read.

I though that the Drive chip may be bad, but I know that other chips in the
Mega also have something to do with Drive signals. I think the Sound
Chip and maybe the Video Shifter relate drive signals, but not sure
what part each control?

And does the keyboard have anything to do with the drives?

The Mega is a version 5.0xxx motherboard. with TOS 1.4.
Stock unit with 4megs. Used very little.

.

Hey Barry! I know you've got a lot of other ST stuff lying around - how
about switching out the floppy drive with a known working one? At least
that way, you could rule out the drive, before you started chip-chasing.

The Mega models aren't too hard to take apart.

Hope this helps.

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"Ronald J. Hall" <darkl...@suddenlink.net> wrote in message
news:pan.2008.05.08.14.52.07.149073@suddenlink.net...

Already, switched out the internal drive, with a known working mech.  And
got the same results.
Also tried an original Atari external disk drive and a GoldenImage which all
work fine on
my 1040STe. I replaced the powersupply and it's purring like a panther. I
mean kitten.

I've had the Mega apart, as I was going to do a few upgrades before this
problem came up.

Reason I ask about the keyboard, is I plugged in a TT keyboard before this
problem came up.
Unless all TT keyboards are the same, the one I used seems to be a non-US
version.
Due to what appears to be a Sign for the UK Pound on one of the number Keys.

I then tried a original Mega keyboard but get the same. I think it's a chip
problem.
Btw the mega acts, you'd think it has its NVRAM messed up. But the mega
doesn't
have NVRAM.

If a bad keyboard can mess up the drives then it's possible that I have 2
bad keyboards, I have another
Mega keyboard that I'm getting ready to try just to make sure. Then going
after the Yamaha chip.
Most of the chips in this mega are socketed, maybe ones loose.

.

Well, at least you ruled that out.

<snip>

Could be, sometimes just removing and resocket-ing them is enough.

Good luck.

--
Welcome To DarkForce! www.darkforce.org "The Fuji Lives.!"
An Atari SW/HW based BBS - Telnet:darkforce-bbs.dyndns.org

"Ronald J. Hall" <darkl...@suddenlink.net> wrote in message
news:pan.2008.05.09.13.41.45.311351@suddenlink.net...

I went back over the Mega ST PCB, and it has a problem with a chip or chips
that control
the reading/writing of a disk in the drive. I disconnected the power to the
internal drive and rebooted.
The Desktop comes up instantly without any drive Icons. I went a step futher
and added an
external disk drive (known to work) while leaving the power off the internal
drive.
And rebooted. Again as with the internal drive connected, it takes 1-2
minutes for the desktop
to come up. I can select items from the desktop, switch resolutions, add
devices and etc.
But if I try to read a directory from drive B, then I get the ole error
message that the disk maybe
damaged.  I get the same results from the stock internal disk drive.

So, I'm positive that the internal drive is good. Just a matter of finding
and replacing the correct
damaged chip. I think I have what I need here to track it down, just thought
I'd ask in here to see
if anyone knows for sure which chip in the mega controls the reading/writing
of a disk in the internal/
external drives?

Guess I'll have to dive into a few of my tech manuals for that.

I'd like to fix this Mega as it's a nice one, used very little and has the
stock 4megs.
If someone reading this happens to have a Mega ST that they no longer want
then I'd be
interested in it for parts. I don't have to have the keyboard or the case or
the internal drive for that
matter, a working motherboard will do fine, version 5.0 if possible.

Send me a e-mail with details on the Mega ST that you have to get rid of or
sale to me
at: phant...@bellsouth.net