The PA's, IPA and 2nd multiplier in the BC-640 were VT-204, aka HK24G or 3C24. In the late 60's, I had two of the transmitters complete, surplused out of Barksdale. Robert Downs - Houston <http://www.wa5cab.com> (Web Store) MVPA 9480 <wa5cab at cs.com> (Primary email) <wa5cab at houston.rr.com> (Backup email)