[time-nuts] 5061A Problem Child - It Lives!

EWKehren at aol.com EWKehren at aol.com
Thu Jul 8 03:34:27 EDT 2010


You do not need a pico amp meter all you need is a digital multi meter that 
 has a 10 M ohm input resistance. Bert Kehren
 
 
In a message dated 7/7/2010 9:23:52 P.M. Eastern Daylight Time,  
paulswedb at gmail.com writes:

Completely agree congrats and thanks for the update.
I may be  getting back involved with my 5061a soon now that I have a HP
pico/femto  amp meter.
By golly I will go hunting for the elusive I beam current ghost  directly 
off
the tube or at least learn that I can't.

On Wed, Jul 7,  2010 at 6:29 AM, Didier Juges <didier at cox.net> wrote:

>  Congratulations Joe!!!
>
> Didier
>
> >  -----Original Message-----
> > From:  time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at 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
> >
> >
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> >
>
>
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