[time-nuts] FTS 1200 transistor replacement
Traced the problem of my FTS 1200 to the first BC109 Transistor on the A2/A3 AGS/Amplifier board. Since it is right after the Oscillator transistor low noise is critical. This unit is at least 30 years old and my question is, what transistor will have even lower noise than the than low noise BC 109. Voltage is 6.43 V. Thanks Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FTS 1200 transistor replacement
Hi The 2N5089 from ON semi is a pretty good bet for a high beta / audio part. They are $0.37 a piece from Mouser with 11,542 in stock. Bob On May 17, 2014, at 11:37 AM, ewkeh...@aol.com wrote: Traced the problem of my FTS 1200 to the first BC109 Transistor on the A2/A3 AGS/Amplifier board. Since it is right after the Oscillator transistor low noise is critical. This unit is at least 30 years old and my question is, what transistor will have even lower noise than the than low noise BC 109. Voltage is 6.43 V. Thanks Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FTS 1200 transistor replacement
Bert wrote: what transistor will have even lower noise than the than low noise BC 109. Generally speaking, the baseband noise of a bipolar transistor is most strongly influenced by the transistor's base spreading resistance. Of course, the transistor also needs to have whatever other characteristics are required in the application circuit -- in particular, adequate current gain and transition frequency at the operating point and sufficiently low input capacitance -- and these may be mutually exclusive with lowest base spreading resistance. The 2SD786 and MPSA18 may be good candidates. That said, I seriously doubt you will get usefully better phase noise by using a better transistor in this location. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FTS 1200 transistor replacement
Thanks for all the help. I do have a couple of BC 109 but I thought with all the work to carefully disassemble the unit that after 30 years there would be a better transistor. Thanks again Bert Kehren In a message dated 5/17/2014 6:47:55 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Bert wrote: what transistor will have even lower noise than the than low noise BC 109. Generally speaking, the baseband noise of a bipolar transistor is most strongly influenced by the transistor's base spreading resistance. Of course, the transistor also needs to have whatever other characteristics are required in the application circuit -- in particular, adequate current gain and transition frequency at the operating point and sufficiently low input capacitance -- and these may be mutually exclusive with lowest base spreading resistance. The 2SD786 and MPSA18 may be good candidates. That said, I seriously doubt you will get usefully better phase noise by using a better transistor in this location. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FTS 1200 transistor replacement
Thanks for all the help. I do have a couple of BC 109 but I thought with all the work to carefully disassemble the unit that after 30 years there would be a better transistor. The fundamentals of solid state physics haven't changed much in 30 years;-) It's a tribute to semiconductor scientists that our fabrication processes have been delivering devices with very close to theoretical performance for ~50 years. (But I'm still waiting for commercial graphene FETs.) Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
