Guido, I would like to see the base bias voltage a little bit lower - 0.63 maximum, .62 nominal. I recommend replacing Q11 and Q13. Yes, the current draw without Q7 and Q8 installed is within the normal range.
73, Don W3FPR Guido Tedeschi wrote: > I removed the PA transistors and measured the bias, which is 0.64V and > this should be fine... > Probably, it was only an heatsinking problem, unless the TX current is > wrong: without the PA transistors, with RF Power set to 5.0W (with any > value greater than 0.1W is the same), the TUNE current is 0.62A (0.24A > in RX) > Is it ok 0.62A? > Thanks and 73 > Guido, ik2bcp > > Don Wilhelm wrote: > >> Guido, >> >> Since the normal base to emitter voltage on the PA transistors self >> limits at about 0.63 volts, the best way to check the bias voltage is >> to remove the PA transistors and measure it. With the PA transistors >> out, if the base voltage during a TUNE is between 0.6 and 0.63 volts, >> then Q11 and Q13 are doing their job and you have faulty PA transistors. >> >> For proper heatsinking, yes the PA transistors must fit flat against >> the heatsink. Before soldering the PA transistors in place, I >> position them on their mounting hardware and secure them temporarily >> with a nut (no lockwasher, no thermal pad). That places the tab >> parallel with the RF board. >> Solder the transistors and remove the nuts - add the thermal pads and >> mount the heatsink. >> >> 73, >> Don W3FPR >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
