EPROM issues, who can burn?

> > I agree, mostly, with what you've said here, Tony. The easy fix, in many > cases will be to program the code into several larger but readily

> and easily programmed parts, then wire an adapter from the target board's > socket to the physical EPROM on the board on which the EPROM resides,

> pair of appropriately sized IDC ribbon cable headers crimped on the ends

I'd be a little careful about hanging lengths of ribbon cable off an EPROM socket (the signals on which may well not be buffered). I am not saying it won't work -- many times it will, but I'd not do it unless necessary. Many times there's enough space around the EPROM socket and/or between the boards in the cardcage to allow for a simpler replacement method. The fact that most EPROM pinouts are similar helps here. Tricks include : 1) Bending out those pins of the EPROM that are different (high-order address lines, for example), plugging the rest into the socket and soldering wires to the ones you've bent out 2) Replacing the socket on the board with a wire-wrap socket. Wrap wires around the pins that are different, and cut those pins short. Then solder the remaining pins to the board so that the 'different' ones don't touch the tracks (the socket is probably about 0.5" above the board). Solder the ends of the wires to appropriate points. Insert the EPROM. 3) Make an adapter. In the UK you can get pin strips designed to plug into turned pin IC sockets. What I normally do is replace the EPROM socket on the PCB with a turned-pin one of the same size. Then take a piece of stripboard and solder a socket for the new EPROM to it (cutting the tracks down the middle). Then solder pin strips to the track-side of the stripboard with one spare hole between the socket pins and the pin strips. Then cut tracks for the pins you don't want to connect straight, and then solder wires (wire-wrap wire is good for this) on the track side of the stripboard to make the necessary connections. Plug the adapter into the socket on the PCB and plug the EPROM into the socket on the

4) Ditto, but etch a PCB rather than using stripboard. 5) Read the tech manual for the machine (!). It's not uncommon for machines that use mask-programmed ROMs to have some way of using EPROMs instead. There may be links for this on the board, for example. > from a hanger in the rack. Packaging problems are what the REAL

> work hardest at, while the youngsters conjure up the fancy circuits.

> is mostly a packaging problem. The higher speeds of today's common and > cheap parts will compensate for the few nanoseconds lost in cables, even

I'd be more worried about the stray capacitance and noise pickup from the ribbon cable than the delay it introduces. -tony