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

Pete Lancashire xyzzypdx at gmail.com
Thu Jul 8 10:45:17 EDT 2010


cool congrats !!

-pete

On Tue, Jul 6, 2010 at 9:43 PM, J. L. Trantham <jltran at att.net> wrote:
> 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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