Congratulations Joe!!! Didier
> -----Original Message----- > From: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham > Sent: Tuesday, July 06, 2010 11:44 PM > To: 'Discussion of precise time and frequency measurement' > Subject: [time-nuts] 5061A Problem Child - It Lives! > > Just a wrap up on the 5061A that had a Beam I but no 2nd > Harmonic indication. > > I was originally stymied by swaps of modules with another > 'functioning unit' > with no help. I then swapped CS tubes with A4 Harmonic > Generators attached and A11 Cesium controllers at which point > neither unit worked. I added an > A15 Power regulator swap and still neither unit worked. I > undid the swaps, got the 'functioning unit' working again > (found a leaky A11C2, a 2.2 uF film capacitor with a > resistance of about 1800 ohms, that prevented the 2.8 KHz > Control Oscillator from oscillating), then went through some > tests of both units, assembly by assembly and found A7 > faulty. Problem was a 'weak' Q1 (1854-0023, the input > transistor in a 3 transistor amplifier)) with a Beta of about > 20. An identical transistor at Q2 had a Beta of about 200. > I installed a 2N2222A that had a Beta of about 150 and all > was well. The 2nd Harmonic came up normally but the Alarm > light would not go out. However, when put in Operate, the > Continuous Operation light would come on and the unit seemed > to 'lock' normally. > > I found an open Q20 and a shorted Q22 (both 1854-0003's) on > the A14 Logic Assembly causing the Alarm light to stay on. > Replaced these with 2N2222A's and now all seems well. > > I can't explain why swapping A7 modules early on did not > resolve the 2nd Harmonic indication problem unless both A7's > were 'weak' allowing them to work with a stronger signal but > not a weak signal or all the swapping of tubes, back and > forth, in and out, etc., fixed a dirty connection. On > reflection, probably the latter. > > In any event, it works and seems to be one of my stronger tubes. > > I could not find any cross reference for either of these NPN > transistors but the 2N2222A seemed to do just fine. > > Thanks for everyone's help. > > Joe > > > _______________________________________________ > 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.