[time-nuts] HP Stories: An architectural view of the HP 5060/5061 and awkward oscillator adjustments.

[Rice, Hugh (IPH Writing Systems)]

Several people have asked about the Len Cutler ban on Aluminum Electrolytic Capacitors in HP Frequency Standards.   Rick Karlquist could shed more light on this too.   The legend of the ban was passed along to me, perhaps by Lou Mueller, who liked to tell stories of the old days.   In 1985, we were not taking the ban literally.   For example, the 2400uF main power supply filter capacitor was AL-Electrolytic, as were a few other smaller capacitors on the power regulator.   I sidestepped the capacitor issues on my simple battery charger by not having a filter cap after the transformer/full-wave-bridge, and just used 120 Hz pulses, since the battery didn't care about DC vs. pulsed DC.   (I thought it was pretty clever to leave out the main filter cap.)     Where possible, Tantalum capacitors were used.    For the few places where AL caps were used, they were heavily de-rated, operating at 50% of rated voltage for example.

As one reader pointed out, back in the 1965 when the 5060A was developed, AL-Electrolytic caps were likely a lot less reliable than in 1985 when I worked on the 5061B.


From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Rice, Hugh (IPH Writing Systems)
Sent: Saturday, February 23, 2019 8:49 PM
To: time-nuts at lists.febo.com
Subject: [time-nuts] HP Stories: An architectural view of the HP 5060/5061 and awkward oscillator adjustments.

Hello Time-Nuts,

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It was fantastically reliable. Only linear power circuits, with robust heat sinking of all power devices. The legendary Len Cutler ban on aluminum electrolytic capacitors. 5060s were still in use in 1985, after 20 years of constant operation. Likewise, 5061As were abundant in time standards for 25+ years until they were replaced by the 5071A in the 1990s.