Many thanks for your suggestions regarding my problems. The original Rombox had eight ROM sockets but no cartridge slots and this is the one which you repaired. My Rombox is a later type with four ROM sockets and two cartridge slots.
Since I wrote my appeal for help, I have had another attempt and it would seem that the fault is now cured. It seems to have been due to the contacts of the edge connector on the Rombox. I had tried to make contact better by poking them together with the point of a scriber but this wasn't very satisfactory and did not completely cure the fault. I have now used a pair of pointed tweezers so that each pair of contacts could be squeezed together and so make better contact.
I suppose that it would be better to replace the edge connector but, as you say, the plastic case is stuck together and I am reluctant to open it up.
Regarding the cleaning of the edge connector on the Elk. I have got the Cleaning Pad (Maplin FB81C) for cleaning edge connectors. This is an impregnated tissue in a sachet. I found this easier to use than a pencil eraser as you can fold it around a piece of stiff card for cleaning the top-side without having to dismantle the Elk. As I had already used a pencil eraser, I cannot say whether this made any further improvement at present.
Richard Dimond
One further point on the problem of edge connectors. I had an AP2 and an original Jafa MODE 7 EXPANSION UNIT as well as my Acorn Plus 1 and AP3. I had a lot of edge connector problems. I removed the connector from the AP2 and, using short lengths of wire, soldered the AP2 and MODE 7 DISPLAY UNIT together. I don't advise this. It did work after a while but I needed to do a lot of re-soldering and the finished result is never going to be as good. Also, it is extremely difficult to remove the solder from the gold contacts of the AP2.
Gus Donnachaidh, EUG #23