Mega STE repair

[olivier.jan]

So I got my first Mega STE a few weeks back and I’ve been working on it on and off.
It came without hard drive but the original ACSI-SCSI adapter is present.

What I’ve done so far:

• Cleaning of the Mother board
• Cleaning of the floppy head and lubrification of mechanical parts
• Machine was not booting, so I swapped the original TOS 2.05 with a freshly burnt 2.06
• TOS 2.06 was bombing right after memory tests=> 4 bombs, possibly floppy issue.
• Changed floppy cable: finally booting to desktop!
• Recaped PSU with Exxos kit and replaced the fan with a Noctua=> getting a steady 5.16v at the CPU. I find it a bit high, but I don’t know how to adjust it on Phiong PSU.
• Machine was hanging after a few mins, I realized the CPU was getting burning hot. Cleaned the socket and replaced with HC variant, now everything is cool and no more freezing.
• Programmed a GAL and added a 68882 FPU.

Next on the list:

• Replace the original power and HD LEDs which are totally rusted
• Mod the ACSI-SCSI Adapter to support drives bigger than 1Gb
• Add an internal HD replacement

I haven’t modded the SCSI-ACSI adapter yet as I want to make sure everything works before, but so far I’m getting nowhere
With the 3 dip switchs ON and an SCSI2SD connected, I can’t manage to get it to work

SCSI2SD is version 5.0 with 1 device of size 512Mb, I tried different SCSI IDs, removing the bus termination, changing to Slow mode, but it simply doesn’t work. I manage sometimes to have it detected using PPDriver, but it doesn’t even display the drive size, just vendor ID. With HDDriver 11, it’s not even detected.

Is there any specific setting for SCSI2SD to get it to work with Atari ?

[Steve]

Be careful with the Noctua!! Your PSU will definitely go bang if you're using silent mode.. Make sure it's definitely sucking air outside of the PSU case and out the back, use medium/high speed.

[Steve]

Here is a post I made many years ago, I have photos and configuration details, you need to use hd driver v9.06 or 9.1:
https://www.atari-forum.com/viewtopic.p ... 1&start=25

[Darklord]

You could install a mass storage device like:

https://lotharek.pl/productdetail.php?id=47

https://lotharek.pl/productdetail.php?id=49

One big advantages is that you do away with the
limits from the original controller and have 2 SD
card slots. Fairly large sizes have been established
as working fine. I use 2 and 4 gig cards but others
have used much higher with no problems.

Also, when you go to replace your LED's, you might
want to look at this message thread:

https://atariage.com/forums/topic/30093 ... /#comments

It's a long thread but lots of good info there, and it evolves (devolves? ) into info
about using the internal US with the Mega ST towards the end.

HTH's.

[olivier.jan]

Good progress tonight, I finally got SCSI2SD to work properly with version HDDRIVER v11.
Here are the details if it can help:

• I have an SCSI2SD v 5.0a with latest firmware for this model (4.8.4)
• I use a 16Gb Micro SD (SanDIsk)
• I needed to check « Enable SCSI2 Mode » to get it properly detected by HDDRIVER.
• I created 4 different devices on the SCSI2SD with ID 0,1,2,3 each device was slightly below 1Gb (1000 Mb) because of ACSI-SCSI adapter limitation.
• With the above settings I was only able to see the first device
• Checking « Map LUNS to SCSI IDs » finally gave me access to all 4 devices

Not sure I’ll go for the adapter mod as 4Gb is already a lot for the ST, moreover I’m not sure the HDDRIVER will work with this mod.
Next step is now to look at the displays as I find it pretty dim and can see some ghosting. I’m using the cheap VGA adapter from Exxos connecting to an OSSC. I’ll check with direct SCART tomorrow to make sure the adapter is not the culprit.

[Darklord]

As it is, you're going to have several partitions as TOS v2.06
will only support up to 512 meg sizes by itself.

On the 4 gig SCSI hard drive I use on my Mega ST4, with
TOS v2.06, I have:

C, D, E, F, G H, I, J, AND K.

I also have L for an EZ-134, M for a 2 gig RAM disk, and
P for a 2X SCSI CD-ROM burner. (this isn't counting the
A and B icons for floppy drives and an icon I use to launch
DarkForce, my BBS).

It's quite crowded on the desktop on that machine.

[olivier.jan]

The machine is now fully repaired and working fine.
I was considering adding a VGA card and O finally found an affordable ET4000 this week, now I need to find the VME bus adapter
And because it was not enough, I just picked up last weekend another Mega STE for 50€

[olivier.jan]

So I refurbished the new Mega STE over the week-end, cleaned it, replaced broken par, added memory modules and an FPU (with associated GAL).
I tested and everything works, Sysinfo and GEMBENCH (4) recognise the FPU correctly.

But I just realised this morning that I forgot to remove Jumper W3.... I've been searching through the schematics and can't find it.
Anyone has an idea why it works with the Jumper ON ?
Anyway, I'll remove it tonight, but I just wanted to understand.

Olivier

[olivier.jan]

Going back to my first Mega STE which hasn’t been used in weeks, I had a bad surprise turning it on today: the hard disk was not recognized. I tried changing the cable. Pushing all the chips in their sockets, etc…
So I finally tried the ASCSI-SCSI with its SCSI2SD in the second Mega STE and it worked well.
Putting it back in the original one it worked too, until it didn’t… Sometimes it works sometime it doesn’t, it even stops working while the machine is working and starts spitting error message saying my disk is damaged.
So far I suspect a bad solder joint somewhere or a DMA issue.
I will reflow all solder joints on the ACSI-SCSI board and the motherboard connector just in case. If someone has another idea…