in previous post "..and considering ..". should read "...and I am considering ..." Is it possible that they are temperature compensated biasing. Still not 100% happy as does not explain how the thermal shutdown works. Justin On 5 September 2016 at 15:42, Justin Richards wrote: > I have confirmed with both the schematic and the actual amp that the > collectors are tied to the bases and both transistors bases are tied to > each other,. > > It remains a mystery and considering that they are used in some way to > provide diode volt drops that match another pair of the same transistors > that are closely bonded on the same heat sink. > > I would like to make the manufacturers schematic available but I have bee= n > asked not to do so. > > Justin > > On 5 September 2016 at 11:08, RussellMc wrote: > >> Are collectors really joined to bases, as shown? >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .