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Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 16:44
by polbit
Well, after I disabled on-board memory with the resistors and attempted boot, the machine would show nothing, wouldn’t even seek floppy. I wanted to go back to known good state, so I removed the upgrade, and connected the resistors back. Now everything works, but I get thin, black, vertical lines every 1/3 inch or so (mono screen) They don’t move, are completely steady... Any ideas?
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 16:55
by rubber_jonnie
polbit wrote: 11 Aug 2020 16:44
Well, after I disabled on-board memory with the resistors and attempted boot, the machine would show nothing, wouldn’t even seek floppy. I wanted to go back to known good state, so I removed the upgrade, and connected the resistors back. Now everything works, but I get thin, black, vertical lines every 1/3 inch or so (mono screen) They don’t move, are completely steady... Any ideas?
Which resistors did you pull up to 5v? Do you have a picture? Also, if you connect 5v to the the wrong side of the resistors, it won't work.
EDIT:
You need to pull up R59, R60 & R61 at the end furthest from the RAM and connect all 3 to 5v. If you currently have 1MB installed you need to do the same for R71, R72 & R73 as per the guide here:
https://www.exxosforum.co.uk/atari/last/4MBMMU/index.htm
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 16:57
by exxos
You should probably run
YAART You might have bad RAM or just video interference.
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 17:02
by rubber_jonnie
exxos wrote: 11 Aug 2020 16:57
You should probably run
YAART You might have bad RAM or just video interference.
My bet is interference.
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 17:15
by polbit
exxos wrote: 11 Aug 2020 16:57
You should probably run
YAART You might have bad RAM or just video interference.
Ran two passes, RAM is OK.
Tried two shifters, reflowed all legs of the socket I had to install for it.
The only other change I’ve done is install a blitter socket (no blitter yet) but I did not open up the vias, so I don’t think that would impact it. The computer worked perfectly fine yesterday...
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 17:40
by exxos
Is your power supply recapped at least ? ... But I think you are drifting onto another topic here relating to video interference not RAM issues.
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 18:03
by polbit
exxos wrote: 11 Aug 2020 17:40
Is your power supply recapped at least ? ... But I think you are drifting onto another topic here relating to video interference not RAM issues.
I am using a Mean Well RD-50A for PSU right now, and it works fine in my main 1040STF with 4Mb RAM.
Re: 4Mb MMU Socket Upgrade questions
Posted: 11 Aug 2020 20:32
by exxos
Well video issues you should open up a new topic and concentrate on the ram issue in this thread. But noise on the video is a inherent issue on most machines anyway, so its unlikely fixable.
Also as mentioned, please post a image of how you disabled the onboard ram.
Re: 4Mb MMU Socket Upgrade questions
Posted: 12 Sep 2020 13:20
by polbit
I just fixed a 520STF motherboard (replaced CPU), and want to attempt upgrading with the 4Mb kit again. With that said, can someone tell me exactly which 68R resistors do I need to lift and tie to 5V? This MB seems to have few extras...
20200912_081413.jpg
Re: 4Mb MMU Socket Upgrade questions
Posted: 12 Sep 2020 13:26
by exxos
It will be the 68R ones..