In message , Peter L. Peres writes >> how do you switch that SCR off? Turns out, you switch >> a capacitor across the device which diverts the current >> around it for just a few micro(?)seconds and that's >> enough to turn it off. Pretty impressive, I thought. > >Barry, the two-thyristor scheme was used extensively for horizontal >deflection and HV circuits before HV transistors were available. Try to >get hold of a Grundig color TV set schematic from about 10-15 years ago. >Maybe Roman has one. It's a neat scheme. Of course the theory is discussed >in contemporary application notes (from ITT and others). As someone who has been repairing TV's for over 30 years I have to disagree with that statement. Thyristor line output stages were extremely rare, only a very small number of manufacturers used them (Grundig was one of them) - most TV's were using transistor line output stages years before the twin thyristor circuit. The UK Thorn (Ferguson, HMV, Ultra etc.) company (long since defunct!) produced the worlds first all transistor colour TV around 1968/69, the 2000 series - a dual standard 405/625 receiver. At that time all other sets (including Grundig) made extensive used of valves (tubes!). We are actually a Grundig agent, their two thyristor design didn't appear until 4 or 5 generations of Thorn all transistor sets had been available. Most other UK manufacturers had also switched to transistors by that time. -- Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : nigelg@lpilsley.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.co.uk | | Chesterfield | Official site for Shin Ki and New Spirit | | England | Ju Jitsu | \--------------------------------------------------------------/ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body