SS Posted February 13, 2021 Share Posted February 13, 2021 So I took a chance on this "untested" MicroRam 64K module for my 600XL. It of course doesn't work. SYS-Check is telling me that some of the RAM (equivalent to U10 & U11 ???) is bad. Unfortunately, I cannot see any way to open the thing up to do any physical checking; there are no screws to be seen anywhere. Anyone have any experience with this thing and/or any ideas? Thanks. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted February 13, 2021 Share Posted February 13, 2021 @SS Can you take a pic of the PCB inside? It looks like if its 2 DRAM's (2x4464), 1 of them are bad. If its 8 DRAM's inside (8x4164) 2 of them are bad. If the DRAM sockets are sequentially numbered on the silkscreen, you might be able to isolate which ones are bad by swapping chips and tracking if you can get the "Red" ones to move around in the Sys-Check diagnostics corresponding with your actions. Quote Link to comment Share on other sites More sharing options...
BillC Posted February 13, 2021 Share Posted February 13, 2021 (edited) 2 hours ago, SS said: Unfortunately, I cannot see any way to open the thing up to do any physical checking; there are no screws to be seen anywhere. Anyone have any experience with this thing and/or any ideas? I have an MPP 1000E Modem that doesn't have any screws as well, I found carefully working with some spudgers(used for prying open laptops/cell phones/etc) starting at one end and working my way around that the 2 case halves separated. The tool should be a softer material to avoid damaging the case, a popsicle stick or similar should also work. The picture below show small solid posts that fit into larger hollow posts on the other half, since both are MPP products they likely use the fastening method. Edited February 13, 2021 by BillC 2 Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted February 13, 2021 Share Posted February 13, 2021 @BillC Wow that 1000S is very sparsely populated inside ! The PCB on the 830 has way more components, and does less! I guess the fact it is TTL to the computer's PIA removes the need for RS232 voltage level conversion though. And direct connect to phone line removes need for all the mic/speaker supporting stuff. 1 Quote Link to comment Share on other sites More sharing options...
SS Posted February 13, 2021 Author Share Posted February 13, 2021 9 hours ago, BillC said: I found carefully working with some spudgers(used for prying open laptops/cell phones/etc) starting at one end and working my way around that the 2 case halves separated. The tool should be a softer material to avoid damaging the case Thanks for the advice Bill. I just ordered a set of these "spudger" tools from Amazon and will see if I can make any headway with them. @Nezgar - If I can manage to get the thing opened up safely then I will post a picture of the board. Quote Link to comment Share on other sites More sharing options...
+Allan Posted February 14, 2021 Share Posted February 14, 2021 On 2/12/2021 at 9:33 PM, SS said: So I took a chance on this "untested" MicroRam 64K module for my 600XL. It of course doesn't work. SYS-Check is telling me that some of the RAM (equivalent to U10 & U11 ???) is bad. Unfortunately, I cannot see any way to open the thing up to do any physical checking; there are no screws to be seen anywhere. Anyone have any experience with this thing and/or any ideas? Thanks. Did your MicroRAM come with a manual? Quote Link to comment Share on other sites More sharing options...
SS Posted February 15, 2021 Author Share Posted February 15, 2021 @Allan - No manual, just bare bones. @BillC - The spudgers worked perfectly. Thanks for the heads up, I would have never thought of this myself. @Nezgar - Attached are some pictures of the PCB. It looks like a few of the chips are in sockets but most are soldered down. Now I have to figure out what's what and what replacements that I might be able to get my hands on for them. Any ideas here would be greatly appreciated. Thanks. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted February 15, 2021 Share Posted February 15, 2021 @SS Excellent! All is clear now. Those 8 4264 chips are your 64Kx1 DRAMs.... But unfortunately they're all not socketed, so you've got a job ahead of you there to desolder and socket to repair.... Two of them are bad ... and Mt DRAMS too which are notorious for failures in XE's. With some careful analysis of the pcb traces we could probably make an educated guess which 2, but probably better to replace all 8 together which is standard recommendation internally in XLs/XEs... Quote Link to comment Share on other sites More sharing options...
SS Posted February 15, 2021 Author Share Posted February 15, 2021 @Nezgar - Thanks for the confirmation, that is what I was thinking. I found these on eBay. I am pretty sure that this is what I need. https://www.ebay.com/itm/5pcs-MT4264-20-MT4264-IC-Chip-DIP-16-/173752779963 Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted February 15, 2021 Share Posted February 15, 2021 2 minutes ago, SS said: @Nezgar - Thanks for the confirmation, that is what I was thinking. I found these on eBay. I am pretty sure that this is what I need. https://www.ebay.com/itm/5pcs-MT4264-20-MT4264-IC-Chip-DIP-16-/173752779963 Yep those will do. But you need 8 not 5 extras can't hurt though. And 16 pin sockets, you choice dual wipe or pay a bit more for machine sockets. 1 Quote Link to comment Share on other sites More sharing options...
BillC Posted February 15, 2021 Share Posted February 15, 2021 (edited) 2 hours ago, SS said: @Nezgar - Thanks for the confirmation, that is what I was thinking. I found these on eBay. I am pretty sure that this is what I need. https://www.ebay.com/itm/5pcs-MT4264-20-MT4264-IC-Chip-DIP-16-/173752779963 I recommend staying away from the MT4264 as they are well known for high rate of failure, at least those purchased by Atari are. The common generic part# is 4164, they are 64kx1bit DRAM. 41256(256Kx1bit) are pin compatible except for pin 1 which should be grounded. I mention the 41256 since they are often available for less than the 4164. Both are readily available on eBay, and also on Jameco if you want a more reputable(but also more expensive) supplier. Jameco would likely be faster as well since it is in stock in the US. 4164 @ eBay 41256 @ eBay 4164 @ Jameco 41256 @ Jameco I just remembered ABRA Electronics which has locations in the US and Canada: 4164 @ ABRA 41256 @ ABRA Edited February 15, 2021 by BillC Fix links 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 15, 2021 Share Posted February 15, 2021 (edited) heh mt's replace them all.... I'd double the memory on that card and run a line from the 600XL mother board to the pbi opening to support it. Edited February 15, 2021 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+Allan Posted February 16, 2021 Share Posted February 16, 2021 Ironically (or not) this popped up on ebay : https://www.ebay.com/itm/Vintage-MPP-Memory-Board-For-Atari-600XL-Micro-Ram-64k-Microbits-Peripheral-Prod/373461673973?hash=item56f40ce7f5:g:jQwAAOSwgKpgKvpN Quote Link to comment Share on other sites More sharing options...
+slx Posted February 16, 2021 Share Posted February 16, 2021 20 hours ago, Allan said: Ironically (or not) this popped up on ebay : https://www.ebay.com/itm/Vintage-MPP-Memory-Board-For-Atari-600XL-Micro-Ram-64k-Microbits-Peripheral-Prod/373461673973?hash=item56f40ce7f5:g:jQwAAOSwgKpgKvpN .Nice if pricey collector's item with all those accessories but a bit steep if you just want more RAM Quote Link to comment Share on other sites More sharing options...
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