[time-nuts] Aging 5065A ?

[paul swed]

Hi Bob like the DDS pcboards?

On Wed, Oct 7, 2020 at 10:40 AM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> People have successfully mounted eBay synthesizers in 5065’s. They work
> and it is one way to take care of that.
>
> Bob
>
> > On Oct 6, 2020, at 10:49 PM, paul swed <paulswedb at gmail.com> wrote:
> >
> > Will agree I would hack something in. The same for the synthesiser. I
> could
> > swear someone on time-nuts already has. The phase detection circuit is
> > audio and it would take some experimentation. I think Corby supplied an
> > alternative approach on the A7 opamp so a lot of good work.
> > But the charcoal problem mentions really would be the worst problem to
> deal
> > with. I guess it would be ebay parts. $$$ Whats a dead 5065 go for
> chuckle?
> > Regards
> > Paul
> > WB8TSL
> >
> > On Tue, Oct 6, 2020 at 6:27 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> >> Hi
> >>
> >> Replacing the synthesizer with something more modern is certainly
> >> possible. I have
> >> a project (slowly moving along) to do just that. There is nothing crazy
> on
> >> the logic board,
> >> it could easily be replaced with something more modern for not a lot of
> >> money.
> >>
> >> The phase detector / photo amp / modulator chain is a bit more
> >> problematic. My guess is that
> >> a replacement of both the photo amp (preamp) and the phase detector at
> the
> >> same time
> >> would make sense. Both are “audio” circuits. There is nothing in them
> that
> >> makes them
> >> totally nutty to replace.
> >>
> >> The physics package *is* the long term question. When the lamps die, I
> >> doubt we can find
> >> ( or fab) replacements. If the temperature controller fails in a fashion
> >> that the entire “tube”
> >> turns into a chunk of charcoal, that would be a long tough fixer upper.
> >>
> >> Fun !!!
> >>
> >> Bob
> >>
> >>> On Oct 6, 2020, at 3:39 PM, Ulf Kylenfall via time-nuts <
> >> time-nuts at lists.febo.com> wrote:
> >>>
> >>>
> >>> Having been shut of for several months I fired up the
> >>> refurbished 5065A a few weeks ago.
> >>>
> >>> It has since been equipped with a new AC-amplifier
> >>> (A7) and a new Rubidium cell with the repaired lamp
> >>> (thanks to Corby Dawson) and a receiver with a
> >>> TED that was connected according to HP instructions.
> >>>
> >>> Also the 5 MHz original crystal oscillator has been replaced
> >>> with an 10811 upgrade kit.
> >>>
> >>> Almost immedeately, the FET's in the 60 MHz Multiplier A3
> >>> not replaced during the first repair all failed.
> >>> They were replaced with metal can 2N4416 and all was well.
> >>>
> >>> The next thing that happened was that the amber
> >>> pilot light "Continuous Operation"
> >>> went out. From just a single event, the lamp started
> >>> going out just every time I turned my back on the
> >>> instrument. Since there were no sign of out-off lock
> >>> conditions and I had no clue other that removing the
> >>> logic assy A14 and checking the lamp driver Q18
> >>> (1854-0003, selected from 2N1711) I found the transistor
> >>> to be leaky. After replacing it with a 2N1893, I have
> >>> only had one single such event in a week. Looking at
> >>> the 1854-0003 from the bottom, the TO-5 package is most
> >>> likely sealed with brown epoxy. And the A14 board
> >>> is littered with them.
> >>>
> >>> I could of course replace all these
> >>> small signal transistors, be it NPN or PNP with modern
> >>> types  but contemplating on this, I wonder how long a 5065
> >>> can be operational if the heater windings in the Rb cavity
> >>> remains OK and the synthesizer with its unobtanium
> >>> logics are OK. From the records on the inside
> >>> of the meter and switch parts on the front panel, I can
> >>> see that the photo current of the original unit
> >>> slowly decreased over the years. I have one more
> >>> Rb TX unit but the Rb bulb in that one is really "brownish"
> >>> and not in any way clear as the one presently used.
> >>>
> >>> Standard "non-critical" semiconductors can of course
> >>> be replaced, even the integrator IC. But what about
> >>> transistors in the phase detector assy A8? There
> >>> are some oddly looking packages and trying to find
> >>> data sheets only returns bad photocopies from
> >>> years ago, not really detailing what criteria
> >>> I should be looking for.
> >>>
> >>> Many web-pages from time nuts displays modern
> >>> versions of the 5065 (digital clock). The one
> >>> in my lab dates back from 1968 so it is over
> >>> 50 years old.
> >>>
> >>> Any research made on possible replacement
> >>> types for those exotic semiconductors used
> >>> in the critical parts as eg. the phase detector?
> >>> Best Regards
> >>> Ulf KylenfallSM6GXV
> >>>
> >>>
> >>>
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> >>
> >>
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