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Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 12 Aug 2020 02:12
by exxos
@kludge maybe if you can take some install images I can add them to my site ?
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 12 Aug 2020 02:24
by 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
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 03 Sep 2020 00:05
by KLund1
exxos wrote: 12 Aug 2020 02:12
@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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Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 03 Sep 2020 00:12
by exxos
:bravo: :thanksyellow:
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 14 Jun 2026 08:20
by macsonny
Did you tie R65, R66, R68 add R70 to 5 VDC to disable the on-board RAM?
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 14 Jun 2026 08:50
by rubber_jonnie
macsonny wrote: 14 Jun 2026 08:20
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.
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 16 Jun 2026 06:10
by 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
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 16 Jun 2026 09:02
by DoG
macsonny wrote: 16 Jun 2026 06:10
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.
Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 16 Jun 2026 11:42
by 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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Re: MEGA ST RAM UPGRADE NOT WORKING
Posted: 16 Jun 2026 13:32
by rubber_jonnie
exxos wrote: 16 Jun 2026 11:42
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.