MEGA ST RAM UPGRADE NOT WORKING

[exxos]

@kludge maybe if you can take some install images I can add them to my site ?

[Tomswork]

RPD-60A MEANWELL AC-DC Dual output Medical Open frame power supply, Output 5VDC / 5.5A +12VDC / 2.2A

Check the size chart there are smaller one

Tom

[KLund1]

@kludge maybe if you can take some install images I can add them to my site ?

Here are some install pics. If you need some others, please let me know. There is a file size limits here so these are mid-res.
Note the notch I had to file out of the PSU PCB. It gets close the underside trace, but not quite. There is about a 1.5mm gap still there.
I hope this is helpful you and others.

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[exxos]

:bravo: :thanksyellow:

[macsonny]

Did you tie R65, R66, R68 add R70 to 5 VDC to disable the on-board RAM?

[rubber_jonnie]

Did you tie R65, R66, R68 add R70 to 5 VDC to disable the on-board RAM?

These are the resistors you need to tie to 5v:

Screenshot_2026-06-14-08-47-02-96_df198e732186825c8df26e3c5a10d7cd.jpg

If fitted I think you need to do R74 as well.

[macsonny]

Thanks for the helpful information.

In the 4th photo it looks like R65 is also connected to 5 VDC. Is that required or not?

Screenshot 2026-06-16 at 3.11.26 pm.png

[DoG]

Thanks for the helpful information.

In the 4th photo it looks like R65 is also connected to 5 VDC. Is that required or not?

R65 is WE (write enable) and it doesn't matter if you connect it to 5V or not. Not needed really.

R66, R68 add R70 is CAS1, RAS1L, RAS1H signals. CAS is not needed either but to be safe people usally tie that to 5V as well.

[exxos]

One word of caution here, we should not get in the habit of using resistor numbers to determine which ones are lifted or not. Generally because resistor numbers can change between revisions of motherboards You should only go on "location" of the resistors, not directly go looking for numbers.

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[rubber_jonnie]

One word of caution here, we should not get in the habit of using resistor numbers to determine which ones are lifted or not. Generally because resistor numbers can change between revisions of motherboards You should only go on "location" of the resistors, not directly go looking for numbers.

Yes that's a very good point. If you can use a schematic for your specific machine to understand where the RAS/CAS signals as @DoG mentioned then you can figure out how the resistors are numbered and therefore what you need to lift and tie to 5v.

Make sure you lift the MMU side of the resistor not the RAM side as it'll be going the wrong way if you lift the RAM side.