After getting some blank discs and using ADT to burn some software, I'm finding out that my IIc has a few quirks at times. The biggest culprit being that there is an exclamation mark in the middle of the screen any time I am in 80 column mode. I cant find any information about this issue from anyone else online, but I do see that a lot of times users will have 2-3 exclamation marks on various parts of their screen usually due to a RAM issue. Though not as bad as some people's cases, it was worth doing some diagnosing to check if any internals were going bad.
I ran the self test and sure enough aux ram chip 00000001 is giving errors. If I run the test again after the computer has been running a bit longer, I get a similar "*RAM 00000111" error, and I've heard that adjacent chips can cause others to read as failing, so either way, some of these aux ram chips need to be replaced.
I think I'm going to try replacing the first 4 aux ram chips first, using decent sockets and new 4164 chips. After seeing videos and reading of people's horror stories burning their own boards up, I plan on being extremely careful. I've soldered and desoldered for a good number of years so far, but working on something this old and sensitive makes me want to ask some veterans and start out on the right track.
If any of you have had to replace RAM in your Apple II before, what chips and sockets do you recommend? I live in the US so I would like to use a reasonable US supplier. I know I have a lot of options (Mouser, Jameco, taking a risk with eBay), but I want to hear your thoughts, especially in this new day and age 2025 since after COVID the industry is a little different. I especially wonder about sockets, since not every dip socket is made the same. I was thinking I would just get a big pack off Amazon, but some have had a horrible time mounting "cheap" sockets and ended up making things worse. Any recommendations for sockets to use are greatly appreciated.
You will want to use a low profile socket so your RAM doesn't come in contact with the disk drive. You do however want to select a low-profile socket that will accept the lead length of the RAM chip itself. I recommend the Mill-Max 115-47-316-41-001000. Mill-max does make an even lower profile socket (115-47-316-41-003000), but the depth of the contact clip does not allow a standard DIP IC to be inserted fully. I usually order Mill-Max from Mouser.
For RAM, most any 4164/4264 200nS or faster should be fine. Because pin 1 (unused on a 4164) is grounded, you could even use less expensive 41256 RAM in place of the 4164 (but you would still only be accessing 64/128K of memory). For NOS RAM, look at Jameco and Unicorn.
Check the Mill-Max 115 series, you'll still need to make some decsions about which vaiant you'll need but understanding dissimilar metals will be helpful. That means don't mix and match tin and gold plating, stick with whatever's on the chips.
Yes, if you have experience with rework, then you'll surely know DIPs are often the greatest PITA parts... so many pins to get free at once can be tough for the novice, hell tough for the pros sometimes too!
Give Jameco a look for replacments, you may have trouble sourcing some of these parts from the big guys (mouser, digikey, etc) . I'd also avoid Amazon as you don't know the source of any of those parts... same for ebay, but for some reason I've found far more Chinese sellers on Amazon passing off as being US so... those parts are often crap (ie it's a waste of your time). If you go with Jameco, just need to test the parts (really need to do this for all parts, everytime, before installing) if you have problems they're good at resolving the problem. They have old stock, so there can be issues but they stand behind their products.
If you want to drill down into what exactly is happening with your RAM I'd suggest looking into the monitor RAM test if you can boot and get into the monitor. Very helpful becaus the ROM RAM test is crap and known to not work well. The monitor test (Jim Sather's) does a decent job of identifying what memory isn't work well. And this only works easily for the lower 48K. There are ways to test aux-RAM but... that's not something that should block you from basic functionality. The reason why I find this test so beneficial is because the patterns are clearly displayed (if you know what you're looking at).
As an example, your "!" instead of " " would suggest you got a stuck bit as the hex values for each character differ only by 1 which would mean bit0 is sometimes not being read correctly by the video generator. So when a space should be displayed the RAM is being read with the low bit high and the video generator is putting out the ! character instead of the space.
I found I have a stash of several dozen 4164 chips... However, I doubt anyone would be interested in any of them because they are... MT.
I think the TI chips on Jameco might be my best bet. Thanks everyone for the socket recommendations, those Max Mill versions look great, just a bit pricey!
And I'll check out a better ram test, but I could definitely use a program that can check ALL the chips, if they made such a thing. It would be nice to know if any of my main RAM is going bad as well. I'll try to research some good tests.
Also, is there any RAM upgrade options for the first motherboard revisions of IIcs? I have ROM 0 but my computer has the board without the expansion slot.
There is this one. His stuff is more or less always out of stock. But if you email him what you are looking for, he supposedly builds small batches. Keep in mind 99.9% of A2 software won't take advantage of this. It's mainly for RAM disks and some productivity software like Apple works.
https://www.a2heaven.com/webshop/index.php?rt=product/product&path=73&product_id=146
Thanks, I hope he still makes these in the future! It would be nice to have that RAM disk functionality.