Notes on the 1541-II

The 6502 RAM/ROM expansion board can also be used in the 1541-II, if it is built with special components, most importantly the low-profile socket adaptors. Only with these a socket can be put into the 1541-II board, otherwise you'd have to solder in the normal socket adaptor directly! The ROM of the 1541-II has to be removed, because it is always installed in a socket and would be in the way. Maybe you have to shorten the wires of some chips or sockets after soldering them, if they collide with underlying chips.

With these special low-profile socket adaptors, the expansion will even fit into a 1541-II with the belt-driven Newtronics D500 mech, though there is only about 1mm space left between them. With the other method (direct soldering of the standard socket adaptor) there is no space left, and you can't use the expansion in the belt-drive version. Ask me for the low-profile version, I have a small stock of them and can supply them for some extra price, together with the precision sockets that you also need.

Of course, the two 6522 chips and the RAM chip cannot be installed in sockets, as you can see in the pictures. A parallel cable has to be soldered directly to the pins of the 6522, preferrably from the bottom side, since you have to cut a trace there anyway.

Here are some pictures to illustrate the usage. You can click on them to get the full size version.

1541-II mainboard
top view with expansion

side view with expansion

Go back to: X1541.DE - Hardware Projects - 6502 RAM/ROM Expansion - Construction Page