Pete, There are two HV power supplies, +3500 (A18) and -2500 (A19), both of which can 'sing'. A18 comes on when power is applied and in CS OFF mode. A19 comes on when you move to any mode other than CS OFF. There is also a battery back up option, Option 002, that has a battery charger board (A2), that can sing when trying to charge 'dead' NiCd's. It comes on when power is applied and in CS OFF mode as well. A2 can be removed with no effect on the rest of the unit to test that theory. When does your unit start singing?
The BEAM I indication can be adjusted by the BEAM I METER pot on the control panel. It only adjusts the meter indication, not the beam current. The beam current can be affected/changed by the C FIELD adjustment and by following the instructions in the manual to align the oven controller (A11) and the Electron Multiplier on the Power Regulator board (A15). Once aligned, adjust the BEAM I METER pot for an 'on scale' indication. This is different on the 5061B where BEAM I METER on the control panel is replaced by BEAM I and is, in fact, the Electron Multiplier adjustment. There are different versions of the A15 board, some of which have a pot to adjust the electron multiplier and others with fixed resistors. The change in BEAM I indication as you adjust the COARSE freq can be very small. The larger the beam current, the greater the fluctuation, but it can still be very small, a division or two. The figures in the manual are quite 'magnified' in my experience. However, I have never played with a 'new' CS tube. The change in BEAM I indication as you adjust the COARSE freq is also very easy to miss and it takes only a very small adjustment of COARSE to go through the entire range. My usual procedure is to let the 5061A warm up for several hours, in the CS OFF mode, make sure the OCXO is stable, then compare it's frequency to that of a GPSDO, then adjust the COARSE freq (with FINE set to 250) to precisely match the GPSDO. I have a TBolt that I use it's 10 MHz to trigger the horizontal of a scope and put the 5 MHz of the 5061A to the vertical. That done, I then select LOOP OPEN, let the CS oven warm up, the BEAM I come up, the 2nd HARMONIC come up, then select CONT OPER and hit the RESET button. If the OCXO is 'on frequency', CONTROL should indicate zero and you should be on the top of the center peak. Adjustment of the COARSE should then be able to demonstrate the 'peaks' to prove you are on the top of the center peak. I don't recall any 'false' modes that will give an erroneous indication. However, I have had failures in the LOGIC board (A14) that have caused indication problems. These units are fun to play with and work on. They make great 'house standards'. I leave them in CS OFF all the time, which lets the OCXO and ion pump run continuously. Hope this helps. Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pete Lancashire Sent: Monday, December 10, 2012 10:59 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] 5061A Beam Current question I've got a couple questions on a early S/N 5061A I got a few days ago. It took a couple days but the Ion Pump current is now down to "zero" or at least less then one division on the meter. I'm able to get the unit to go into continuous operation mode by following the TURN-ON PROCEDURES but have a few qestions 1. The unit 'sings' I'm tone deaf but its a high pitch. It could take some doing to isolate where it is coming from. Any ideas ? 2. How much should the beam current change when turning the OSC FREQUENCY COARSE adjustment ? On time about 45 to 60 minutes The current scribbled on the door is 19, I'm running pretty much 30. When making the adjustment the difference between the peak and any other position is only plus/minus a max of 2 or 3. 3 And i guess for last, are there any false modes that will turn off the ALARM and turn on the Con't Operation light ? Thanks -pete PS Anyone have a side panel without the front handle broken ? _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
