dukes909 Posted February 27, 2021 Share Posted February 27, 2021 So I identified a 16k module in my 48k 800 that was bad. Ok. I bought another 800 off of eBay that had 48k working in it when I got it. I swapped in a card from the new 800 into my original 800 and I get a green screen, won't come on. Take that card out and go back to 32k. I take out all of my original memory and try them in the new 800 - 32k ok. I now try 1 16k card from the new machine in my original 800...nothing but green screen. WTH. I try it back in the 800 it came out of..same thing, doesn't work. I basically go through every card configuration and nothing works except my original 2 16k modules. WTH again?? I take a day off from it come back tonight, now only 1 16k module from my original 800 works. WTH!!! So out of 5 working cards that I started with, only 1 works now. DISCLAIMER: I wear a static strap whenever I swap these things in and out; I don't see how I can be causing it. So barring that, is there some way my 800 is destroying these modules? GGGRRRRR Dukester Quote Link to comment Share on other sites More sharing options...
BillC Posted February 27, 2021 Share Posted February 27, 2021 Have you checked all the voltage outputs on the power supply board, 4116 chips need all 3 voltages to operate, any one of them being out of specification could damage chips. The +12V supply is only used for 4116 RAM, the color adjustment pot, and a power output on SIO, the -5V supply is only used for 4116 RAM and the power LEDs. 2 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 27, 2021 Share Posted February 27, 2021 in addition to checking voltages, please make sure to put memory in the proper slots also 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted February 27, 2021 Author Share Posted February 27, 2021 59 minutes ago, BillC said: Have you checked all the voltage outputs on the power supply board, 4116 chips need all 3 voltages to operate, any one of them being out of specification could damage chips. The +12V supply is only used for 4116 RAM, the color adjustment pot, and a power output on SIO, the -5V supply is only used for 4116 RAM and the power LEDs. I haven't. Where do I check this? Thanks! Quote Link to comment Share on other sites More sharing options...
dukes909 Posted February 27, 2021 Author Share Posted February 27, 2021 39 minutes ago, _The Doctor__ said: in addition to checking voltages, please make sure to put memory in the proper slots also All the RAM cards I have are 16k, and I was only using the first slot past ROM to test each cartridge. Quote Link to comment Share on other sites More sharing options...
BillC Posted February 27, 2021 Share Posted February 27, 2021 3 minutes ago, dukes909 said: I haven't. Where do I check this? Thanks! The power supply board has a 7805 and a 7812 voltage regulator, the -5V circuit is controlled by a zener diode. There is a 33 ohm resistor across the input and output of the 7805 regulator which requires a load to check the voltage, unless you disconnect it first. Since it appears to be only the RAM failing it is likely not the +5V at fault, since that would also tend to damage the logic chips. Schematics are available at http://www.jsobola.atari8.info/dereatari/schematy.htm, they do have some errors but are reasonably accurate. 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted February 27, 2021 Author Share Posted February 27, 2021 10 hours ago, BillC said: The power supply board has a 7805 and a 7812 voltage regulator, the -5V circuit is controlled by a zener diode. There is a 33 ohm resistor across the input and output of the 7805 regulator which requires a load to check the voltage, unless you disconnect it first. Since it appears to be only the RAM failing it is likely not the +5V at fault, since that would also tend to damage the logic chips. Schematics are available at http://www.jsobola.atari8.info/dereatari/schematy.htm, they do have some errors but are reasonably accurate. Before I tear this apart, wouldn't the fact that 1 card works in the first RAM slot indicate all 3 voltages are getting to slots correctly, or is the voltages of the three slots independent of each other? Quote Link to comment Share on other sites More sharing options...
BillC Posted February 27, 2021 Share Posted February 27, 2021 3 hours ago, dukes909 said: Before I tear this apart, wouldn't the fact that 1 card works in the first RAM slot indicate all 3 voltages are getting to slots correctly, or is the voltages of the three slots independent of each other? Not all ICs fail under the same conditions, when I had an INGOT power supply go over-voltage it only damaged 41256 DRAM and all the other ICs were fine. It is possible that the 4116 on the good card were made by a different manufacturer and can tolerate slightly higher voltage. You don't have to open the 800 to check the +5V/+12V outputs, they are available on pins 10/12 of the SIO port, pin 4 being ground. 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 (edited) On 2/27/2021 at 1:14 PM, BillC said: Not all ICs fail under the same conditions, when I had an INGOT power supply go over-voltage it only damaged 41256 DRAM and all the other ICs were fine. It is possible that the 4116 on the good card were made by a different manufacturer and can tolerate slightly higher voltage. You don't have to open the 800 to check the +5V/+12V outputs, they are available on pins 10/12 of the SIO port, pin 4 being ground. Ok so I checked the voltages on pins 10 and 12 of the SIO port. pin 10: 4.96V pin 12: 18.38V Umm, so is the 18.38V the problem, and if it is how do I fix it? Thank you for helping! Edited March 1, 2021 by dukes909 typo Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 Also, interestingly (!), the chips on the good (working) card are 4116's (although there is 1 errant 5290 on that board) like you said! The other cards have either MM5290 or AM9016! 1 Quote Link to comment Share on other sites More sharing options...
BillC Posted March 1, 2021 Share Posted March 1, 2021 (edited) 27 minutes ago, dukes909 said: Ok so I checked the voltages on pins 10 and 12 of the SIO port. pin 10: 4.96V pin 12: 18.38V Umm, so is the 18.38V the problem, and if it is how do I fix it? Thank you for helping! I would say that 18.38V is almost certainly damaging the RAM chips on the cards. There are 2 voltage regulators on the power supply board, the one for the 12V circuit needs to be replaced. The following link is for the Sam's Computerfacts Service Manual, page 6 has an image of the power supply board. The 7812 regulator, A201, is on the left side. http://www.atarimania.com/documents/Sams_Computer_facts_Atari_800.pdf Edited March 1, 2021 by BillC 2 1 Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 1, 2021 Share Posted March 1, 2021 3 hours ago, dukes909 said: 18.38V Ouch! Here's a mod which eliminates 12V and -5V from the RAM board and uses 4164s for 48K on one board: 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 3 minutes ago, ClausB said: Ouch! Here's a mod which eliminates 12V and -5V from the RAM board and uses 4164s for 48K on one board: Thanks! Does the 800 need 12V other places though besides the RAM chips? Quote Link to comment Share on other sites More sharing options...
ClausB Posted March 1, 2021 Share Posted March 1, 2021 Yes, in the color adjust circuit, as BillC mentioned. You should still fix it. 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 1 minute ago, ClausB said: Yes, in the color adjust circuit, as BillC mentioned. You should still fix it. Argh, I didn't scroll up far enough to catch that again. Thanks. AND it explains why my colors are off, COOL! Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 Just now, dukes909 said: Argh, I didn't scroll up far enough to catch that again. Thanks. AND it explains why my colors are off, COOL! Now I just have to find one.... Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 Does the 810 drive use the 12V from the 800? Wondering if this is why I have been having problem with drives as well. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted March 1, 2021 Share Posted March 1, 2021 8 hours ago, dukes909 said: Now I just have to find one.... 7812 voltage regulators are cheap from nearly any electronic supply store. 8 hours ago, dukes909 said: Does the 810 drive use the 12V from the 800? Wondering if this is why I have been having problem with drives as well. No, the 810 has its own on-board voltage regulator. There is next to nothing which uses 12V on the SIO port, which is why it was eliminated on XL and XE machines. 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 1 hour ago, DrVenkman said: 7812 voltage regulators are cheap from nearly any electronic supply store. No, the 810 has its own on-board voltage regulator. There is next to nothing which uses 12V on the SIO port, which is why it was eliminated on XL and XE machines. Thanks I found some at Jameco and Mouser! Well shoot on the 810, but at least I have the RAM part figured out. Are they likely blown or just not working with the high voltage? Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted March 1, 2021 Share Posted March 1, 2021 (edited) alien voice group BOX 1, robotic control system, electrostatic tracing pen and pad, certain paper tape readers and other 800 only devices rely on the 12 volt output. Chances are you won't have any of them... but you never know what card will want it and you would like correct colors... so I'd just fix up the machine like it was intended. The 810 does not use the 12 Volt line... but I wouldn't put the over voltage from back feeding through damaged components and causing issues or even stressing other chips out of spec. making malfunctions like that. Edited March 1, 2021 by _The Doctor__ 2 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 1, 2021 Author Share Posted March 1, 2021 (edited) It isn’t clear to me if the boards that have non-4116 chips are shot or if they will work once I replace the 7812 voltage regulator. If they are dead, I found a source for 4116’s however they are 150ns instead of 200ns that I have now. Will they work?...will they all have to be the same speed? cheers dukester Edited March 1, 2021 by dukes909 Punctuation Quote Link to comment Share on other sites More sharing options...
BillC Posted March 2, 2021 Share Posted March 2, 2021 1 hour ago, dukes909 said: It isn’t clear to me if the boards that have non-4116 chips are shot or if they will work once I replace the 7812 voltage regulator. If they are dead, I found a source for 4116’s however they are 150ns instead of 200ns that I have now. Will they work?...will they all have to be the same speed? cheers dukester There could still be a few good RAM chips on the dead memory boards, but after being subjected to 18V they may have limited life left. Even the RAM chips on the still working board may fail at any time after such treatment. It would be less expensive to convert 2 of the 16K cards to 48KB using 8 x 4164 DRAM on each than replacing the failed 4116 DRAM on all of them, this would require 16 x 4164 + 2 x 7400 instead of 40 x 4116 chips. ClausB already linked a post about this mod. 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 2, 2021 Author Share Posted March 2, 2021 23 hours ago, ClausB said: Ouch! Here's a mod which eliminates 12V and -5V from the RAM board and uses 4164s for 48K on one board: 1 hour ago, BillC said: There could still be a few good RAM chips on the dead memory boards, but after being subjected to 18V they may have limited life left. Even the RAM chips on the still working board may fail at any time after such treatment. It would be less expensive to convert 2 of the 16K cards to 48KB using 8 x 4164 DRAM on each than replacing the failed 4116 DRAM on all of them, this would require 16 x 4164 + 2 x 7400 instead of 40 x 4116 chips. ClausB already linked a post about this mod. Are there any more details on ClausB's mod or has anyone else replaced 4116's with 4164 in an 800? I see the schematic but I am not confident I could build it off of that. (I know I am in trouble when I don't have any idea what Φ2 is or any of those RS4, RS5 & NAND gates!) I see one post says "Look for complete modification instructions in an upcoming issue of pro(c) ATARI magazine!". When I search "48k" on the Atari magazine site I get no results. Quote Link to comment Share on other sites More sharing options...
BillC Posted March 2, 2021 Share Posted March 2, 2021 16 hours ago, dukes909 said: Are there any more details on ClausB's mod or has anyone else replaced 4116's with 4164 in an 800? I see the schematic but I am not confident I could build it off of that. (I know I am in trouble when I don't have any idea what Φ2 is or any of those RS4, RS5 & NAND gates!) I see one post says "Look for complete modification instructions in an upcoming issue of pro(c) ATARI magazine!". When I search "48k" on the Atari magazine site I get no results. PRO(C) ATARI - Issue 15 Softcover-Book Edition UPGRADING AN ATARI 800 TO 48K 1 Quote Link to comment Share on other sites More sharing options...
dukes909 Posted March 2, 2021 Author Share Posted March 2, 2021 2 hours ago, BillC said: PRO(C) ATARI - Issue 15 Softcover-Book Edition UPGRADING AN ATARI 800 TO 48K Thanks. I emailed to ask but there appears to be no online PDF version..? Quote Link to comment Share on other sites More sharing options...
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