Sellam Ismail wrote: I've had a few problems with mine, mostly failing semiconductors, all of which have been unusual and difficult to replace/substitute, although I was quite pleased when I found the 4004 inside. I presume you have the manual, which has the schematic and a listing of the base code firmware. I suppose it's conceivable the 1702 firmware EPROMS are losing their contents. I have taken dumps of the contents of the ones in mine, if of interest. There is a hitch though: various options come on additional firmware 1702s, and some experiments with mine suggested that the base code does not auto-detect the options, rather it appears (one of?) the base code EPROMS is tailored for the particular firmware options installed, so the dumps I have may be valid only for the option set I have. Similarly, if someone has pulled one of the option ROMS in yours, the unit probably won't work. (Is this a new toy or something you know was working? Also, out of interest, which personality module do you have plugged in?) If you haven't used the unit before, you do have to press one of the LIST/DUP/VER/COPY keys initially to get anything to display on the hex LEDs (initially blank on power-up), although I expect you've banged on all the keys already. IIRC, some of the communication adapters if plugged in (serial&parallel D plugs) may cause the unit to appear hung. If all the power supplies levels are OK I suppose the next thing would be to 'scope for multiplex/keyboard scan activity to see if the processor/firmware is functioning.