Bikerbob Posted February 14, 2020 Share Posted February 14, 2020 Hello all, I fixed my one 800xl for my friend - only 1 bad ram chip - lucky! The other one the ram was heating up.. I tested the chips one by one in a known good working machine.. EACH ONE Failed to boot it. Have you seen all 8 ram go bad without something else causing it? I am afraid to put new ram in... James Quote Link to comment Share on other sites More sharing options...
+Stephen Posted February 14, 2020 Share Posted February 14, 2020 Never had a machine where all RAM was bad that wasn't caused by using an incorrect power supply. That being said, usually if I am replacing one chip, I'll do all 8. Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted February 14, 2020 Share Posted February 14, 2020 is it MT brand by any chance? 1 Quote Link to comment Share on other sites More sharing options...
Bikerbob Posted February 15, 2020 Author Share Posted February 15, 2020 No the MT branded ram.. only one chip was bad in that machine. its Mostek 4564-15.. All the personality chips are fine in the machine.. nothing else got hot. James Quote Link to comment Share on other sites More sharing options...
shoestring Posted February 15, 2020 Share Posted February 15, 2020 If the power supply failed or if a c64 power supply was used then yes, I’d suspect all the ram to be fried plus mmu ( at the very least ). drams are quite sensitive to overvoltage and usually die instantly. remove all the ram first then check +5 voltages ( in case there’s still a shorted component somewhere ) before troubleshooting or swapping in new chips. 2 Quote Link to comment Share on other sites More sharing options...
pusakat Posted February 15, 2020 Share Posted February 15, 2020 (edited) When replacing the RAM chips, are the following chips acceptable replacements? TMS4164-12 / MN4164-12 / HM4864P-2 16-Pin Dip DRAM - brand new 64Kx1 bit DRAM TMS4164 - Texas Instruments MN4164 - Panasonic HM4864 - Hitachi Edited February 15, 2020 by pusakat Spelling error Quote Link to comment Share on other sites More sharing options...
Bikerbob Posted February 15, 2020 Author Share Posted February 15, 2020 YES, , one thing I would say and agree.. try and keep all 8 the same.. trying to mix chips does not mean they are bad, but might not work together.. my experience in this thread. To those that were following.. 8 new ram chips in.. machine is good.. mmu was not an issue. James 1 Quote Link to comment Share on other sites More sharing options...
Sikor Posted February 15, 2020 Share Posted February 15, 2020 If it is Freddie machine (C061991-29 - NCR, C061922 - CITEL ) - replace it, probably it is issue. Fault Freddie can damage all DRAM chips mounted in computer in future. Quote Link to comment Share on other sites More sharing options...
shoestring Posted February 15, 2020 Share Posted February 15, 2020 7 hours ago, pusakat said: When replacing the RAM chips, are the following chips acceptable replacements? TMS4164-12 / MN4164-12 / HM4864P-2 16-Pin Dip DRAM - brand new 64Kx1 bit DRAM TMS4164 - Texas Instruments MN4164 - Panasonic HM4864 - Hitachi TI are my favourites but the speed is more important. Try to match the speed that you had in there before or install slightly faster ones. 120ns work fine Quote Link to comment Share on other sites More sharing options...
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