HP, DEC, Olivetti & Apple stuff

The light pne _cable_ is very simple, just a piece of screened cable with a 2-conductor 1/4" jack plug to go into the V14 and a 3.5mm 2-conductor jack plug to go into the light pen [Note for those across the Pond, a 'jackl plug' is the useual name inthe UK for what you call a 'phone plug']. The light pne is just a phototransistor on a long thin PCB with the jack socket on the otehr end. It fits into the metal tube housing. It is possible to take one apart by unscrewing the socket from the housing (although I think there is some kind of threadlock that makes it a little harder). I had a lot of problems with the socket my light pen. In theend I found that the innards from a normal in-line socket would fit the metal pen body, but they went further into the body than the DEC original. I just cut a cm or so off the ned of the PCB. However, there's also a light pen amplifier PCB inside the VR14. It's a single-height flip-chip board that goes in the edge connector block at the back, and has an 8 pin mate-n-lock connector on it for the cable to the ajck socet at the front. I believe this PCB is an option, only fitted if the light pen was used/. Schematics are in the printset if you are crazy enough to try making one. Be warned it's a low-level analogue circuit, and was the part of my GT40 that gave me the most trouble when I was sorting the unit out. -tony