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To construct the RAM module for the USDoubler modification to the Atari 1050 disk drive, purchase two (1 or 2) 6810P RAM's from either Jameco Electronics or JDR Electronics. Jameco is less expensive. You will also need a 2732A ROM to put the USD code into and a PROM burner (or know someone that has one so they can do this for you). NOTE: You can reuse the existing 6810P RAM that is in the U8 socket. However, if something goes wrong, you won't be able to put your 1050 back into it's original configuration without purchasing a new RAM. OK, first bend out pin 10 and pin 14 of one 6810P. Now put the two RAM together piggy back with the RAM you bent the pins out on top.
Now solder all pins together (1 to 1, 2 to 2, 3 to 3, etc...) except for pins 10 and 14 of the top RAM. Go slow and check for solder bridges. Don't leave the soldering iron on any pin longer than 10 to 20 seconds. If you have to make adjustments, let the joint cool down before resoldering (see the diagram above). Now solder a short length of wire (wire wrap wire works well for this) from pin 10 of the top RAM to pin 14 of the Bottom RAM. Also solder a wire from pin 12 of the Top RAM (pin 12 of the Top and Bottom RAM should be soldered together) to pin 14 of the Top RAM. Now check everything and if it looks OK, insert your new RAM back into the U8 socket making sure that pin 1 goes into pin 1 of the socket. Double check this as putting the RAM in backwards will destroy it! Now you will have to change the jumpers behind the ROM at U10 so that there are jumpers in JP2, JP4, JP5 and JP7. Remove the old ROM and save it and install the new 2732A into this socket observing that pin1 goes into pin 1 and so on. NOTE: Before you install the new 2732A, you will have to burn the new USD code into it. You will need a PROM burner or find someone that will do this for you. You also must end up with a checksum of 97D6 or something went wrong. That's it. Now put your 1050 back together and see it it still works. If all went well, you should now have a clone of the original USDoubler and a 1050 that works in true double density. You can find the BIN file for the USD code on the net. I have seen it in several locations which are easy to find. |
