[time-nuts] Aging 5065A ?

[Bob kb8tq]

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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