Exxos PSU (2019), STE 1040 (1991), only works on reset

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kianryan
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Joined: Sun Apr 18, 2021 7:01 pm

Exxos PSU (2019), STE 1040 (1991), only works on reset

Post by kianryan »

Hi all,

I'm installing a new Exxos PSU [0030] in a 1991 1040 STE. This is a STE with a ST processor and all chips soldered on to the board.

This machine was working OK with the stock PSU, but being of an age, I'm keen to replace it.

The new PSU is giving me a nice clean 5V and 12V.

For testing, I've just got the motherboard on a workbench with the PSU attached, and a VGA adapter on the monitor port.

On initial boot on colour, I'm presented with either on-screen garbage (10% of the time) or a plain white/grey screen.
On monochrome, the screen is blank.

However, if I press and release the reset button, I'm immediately dropped in to TOS. The length of time the reset is held down for is irrelevant.

Any ideas why this is occuring, if this is a problem and if there's anything I need to do about it, or if it's a behaviour I'll need to live with?
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Re: Exxos PSU (2019), STE 1040 (1991), only works on reset

Post by exxos »

You need to replace the caps in the reset circuit. Its listed in the fixes section.

https://www.exxosforum.co.uk/forum/viewt ... =17&t=2175
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
kianryan
Posts: 4
Joined: Sun Apr 18, 2021 7:01 pm

Re: Exxos PSU (2019), STE 1040 (1991), only works on reset

Post by kianryan »

Thank you.

This resolved the reboot issue.

Now on to a DMA issue, with a CA401177 (I'll post a separate topic).
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