Mega ST4 not booting after new ram installation

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Forgottenmyname
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Mega ST4 not booting after new ram installation

Post by Forgottenmyname » Wed Apr 11, 2018 9:26 pm

Hi All,

I've just soldered up the 4mb exxos ram board and the Mega switches on just to a plain grey screen.
Quick flash from the floppy light and the reset circuit seems to work ok.

I've checked how I soldered up the shifter board board and I think the problem is there. I've soldered the socket where the pins should be and vice versa. Does this matter, ie are they pin for pin or do I need to swap them over?

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exxos
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Re: Mega ST4 not booting after new ram installation

Post by exxos » Wed Apr 11, 2018 9:30 pm

Did you follow the assembly guide on my main site ?

http://www.exxoshost.co.uk/atari/last/4MBMMU/index.htm

Also assume you inserted the RAM board correct orientation ?
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Forgottenmyname
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Re: Mega ST4 not booting after new ram installation

Post by Forgottenmyname » Wed Apr 11, 2018 9:34 pm

Yes but still managed to get the two sets of pins mixed up. The Ram board is fine, cable exits to the right. Shifter board cable exits to the back, opposite to STFM shown in the instructions. I just mixed the pins up on the shifter board, so that the header pins that go to the motherboard are nearest the white socket and not the socket.

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exxos
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Re: Mega ST4 not booting after new ram installation

Post by exxos » Wed Apr 11, 2018 9:37 pm

If I remember rightly the shifter board is pin to pin.. It was just a breakout board.. I've been trying to find the PCB layout to doublecheck, but I have that many PCBs all over the place and I have no idea the file is called :roll:
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Forgottenmyname
Posts: 40
Joined: Fri Mar 23, 2018 8:22 pm

Re: Mega ST4 not booting after new ram installation

Post by Forgottenmyname » Wed Apr 11, 2018 9:39 pm

Ok, cool, so hopefully I won't need to resolder it :-)
Just find where another loose connection is.....

It won't boot to my dig cart either.

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exxos
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Re: Mega ST4 not booting after new ram installation

Post by exxos » Wed Apr 11, 2018 9:43 pm

Was this the machine use having corrosion problems with ? Is possible there may be some other issues somewhere and besides the RAM ? Also assume you removed all the old RAM as well ?
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Forgottenmyname
Posts: 40
Joined: Fri Mar 23, 2018 8:22 pm

Re: Mega ST4 not booting after new ram installation

Post by Forgottenmyname » Wed Apr 11, 2018 9:45 pm

Yes it was. I'm starting to think that the 2mb ram may have been keeping it working, lol but now its been removed.

Will have to get the scope out again i think.

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exxos
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Re: Mega ST4 not booting after new ram installation

Post by exxos » Wed Apr 11, 2018 10:00 pm

There is a solder jumper on the board to force 1MB.. I think you said it was working but only 2MB before.. So maybe worth a try ?
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Forgottenmyname
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Joined: Fri Mar 23, 2018 8:22 pm

Re: Mega ST4 not booting after new ram installation

Post by Forgottenmyname » Wed Apr 11, 2018 10:04 pm

Good point, will try that tomorrow.

I take it U58 and U59 now don't do a lot either? Is it safe to remove the caps from the old ram too btw?

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exxos
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Re: Mega ST4 not booting after new ram installation

Post by exxos » Wed Apr 11, 2018 10:20 pm

I would leave the caps in, won't do any harm..

I think the chips can be removed.. You would have to double check on the diagram that they are only used for RAM signals.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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