On 05/20/2015 7:15 PM, Richard B. Main, Esq. wrote: Speaking of old textbooks, something people need to keep an eye out for are old parts catalogues put out by the large parts distributors of yore. I have an Electrosonic Catalogues (Canada - 600 some pages of components!) from the late 60s and it is great because they have unarchived specifications on many of the early solid state and EM parts - many of which are used in older computers. One spec sheet I found was a comparison sheet of CDS cells that were common in 1969 and gave their range of specs - handy! The advantage for me is I use these to get the specs on old parts that I am trying to repair, or replace with more modern parts. At one time E-Sonic had a few PDFs of these early manuals online, but they seem to have hidden them since the last time I visited their site. And I just did a bit of a search using Archive.org's wayback machine and can't find the year when they did have those on their site... John :-#)#