[time-nuts] [Bulk] Re: New Guy, has HP 5061A with DATUM 7105A tube seeks advice

J. L. Trantham jltran at att.net
Thu Nov 6 21:18:59 EST 2014


Forgot to mention this on my first post.

On the front panel:

1.  Set the MODE to 'CS OFF'
2.  Set OSC FREQUENCY five turn pot to '250' (not COARSE).
3.  Set MOD to 'ON'.
4.  Set C FIELD to whatever the front door says it should be.

Plug it in and wait.  ION PUMP I will likely (should) go full scale.  Only once it comes close to zero will you be able to advance further.

You can, however, switch CIRCUIT CHECK to its various positions and see what the readings are.

BATTERY will not indicate since you removed the battery and charger card.

SUPPLY will indicate about 3/4 scale or a bit more to indicate that the 18.7 VDC is OK.

ION PUMP I will likely be 'full scale' but, in my experience, the Datum tubes will pump down faster than the HP tubes.  At least give it a couple of days.

OSC OVEN will start full scale but will fall to about 3/4 scale as the 10811 heats up and comes to its operating temperature.  If it does not come down in about 30 to 60 minutes, there is likely a problem with the 10811.

CS OVEN will be at zero until you turn MODE clockwise past CS OFF.  It will then go full scale and after 30 to 60 minutes will indicate similar to OSC OVEN, assuming everything is OK.

5 MHZ should be about 2/3 scale.

MULT will not indicate until you flip the AUTO START - START switch to START and then let it go back, IIRC.

BEAM I and 2nd HARMONIC will not indicate until you are past CS OFF on the MODE switch and the CS OVEN indication comes back down 'on scale'.

CONTROL will indicate when you are in OPER on the MODE switch and have hit the LOGIC RESET button once everything is 'on scale', assuming your OSC FREQUENCY COARSE is 'in the ball park'.  Once you have had the unit plugged in and the OSC OVEN indication has 'come down', you can check the 5 MHz against your GPSDO and then adjust the OSC FREQUENCY COARSE to bring it to 5.000000 MHz.  Once there, the PLL will likely be able to 'lock' and the CONTINOUS OPERATION light should turn green after moving MODE to OPER and hitting the LOGIC RESET button but only after all the other meter indications are correct.  If the light turns green, it is time for the 'happy dance'.

1 MHz and 100 kHz will indicate after flipping the START switch.

Hope this helps.

Good luck.


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Wayne Holder
Sent: Thursday, November 06, 2014 7:14 PM
To: Discussion of precise time and frequency measurement
Subject: [Bulk] Re: [time-nuts] New Guy, has HP 5061A with DATUM 7105A tube seeks advice

> If you get the tube working, you should use a counter or Lissajous 
> display with a GPS or rubidium standard to preset it to the correct 
> resonance peak frequency for lockup.  The tube will probably be pretty 
> noisy at first.  If it also has weak beam current, which is common, it 
> will be very difficult to find the right peak without cheating.

I have a Trimble Thunderbolt GPS Disciplined Clock.  Is that going to be good enough to set the correct resonance peak frequency for lockup?

BTW, thanks for the link to a source for a manual.  I've ordered a copy for my serial number range.

time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

More information about the time-nuts mailing list