[time-nuts] Aging 5065A ?
Bob kb8tq
kb8tq at n1k.org
Wed Oct 7 14:36:49 UTC 2020
Hi
With the advent of cheap PCB houses that also do cheap assembly, the ability to cobble
up this or that has moved from the “nutty” into the “pretty easy” category. Indeed with very
specific parts (integrator cap, fancy op-amp) you might have to hand solder one or two
leaded parts on the board.
On the integrator, with modern op-amps, there are a lot of parts to pick between. A lot
of the stuff that was in the original board went away when HP did the later version of the
integrator. Since that board seems to work just fine, I’d stick pretty close to that design.
One *might* allow for some larger value integrator caps.
I don’t know of many people using the 100 KHz, 1 MHz, or 1 pps outputs from the 5065.
Those empty board locations provide a *lot* of room for expansion projects. There’s also
the battery charger board and the space for the batteries. To me the clock and clock driver
“stuff” is in that same category. it’s a big empty chassis. Not a lot of need to cram extra boards
in by double stacking ….
Yes, each of us gets to do this their way. I’m sure there are several people raising their
hands in exception to at least one item in the paragraph above. I’d still bet at least a
half a bottle of beer that something above 80% of the “running in my basement” 5065’s
line up pretty well with what’s in that paragraph.
====
If you are going to do compensation on the device, you need to feed that comp in
somewhere. Variable C field is one way, but it has it’s issues. A high resolution
synth would be another way. In addition to working out the control approach, you probably
will want some sort of MCU to filter the data. I’d suggest that one of the “abandoned”
board locations is a reasonable place to put all this “stuff”.
So, lots of variables, lots of routes from A to B.
Bob
> On Oct 7, 2020, at 7:09 AM, timeok at timeok.it wrote:
>
>
> Hi,
>
> I would also like to update the 5065A but so far there are no kits or pcb available. I think that the first things to update are also the "simplest ones" like the voltage regulation, the C field generator but first, the integrator board, because there are many old HP5065A that keep the primordial version.
>
> I would like redesign and implement the simplest board, the A9 the integrator.
>
> The main features that I have identified are
>
> 1) the board must be physically compatible with the standard one.
>
> 2) given the large space, provide for a future daughter board that can be mounted with columns anchored on the A9.
>
> 3) smd assembly.
>
> 4) positive and negative regulators 15V.
>
> 5) low noise operational amplifier model?
>
> 6) 5uF capacitor type?
>
> 7) offset regulation?
>
> 8) large breadboard area for future changes ex:pressure sensor to compensate for delta f.
>
> 9) gold coated connector if possible.
>
> I would like to have your opinions, and I turn to all the teachers who read the emails of this group which are many. However, I am available to collaborate with all those interested in updating the HP5065A. I would like there to be some common guidelines, once identified, and projects with a relatively constant flow of work.
>
> thank you,
>
> Luciano
>
> Luciano P. S. Paramithiotti
> timeok at timeok.it
> www.timeok.it
>
> Da "time-nuts" time-nuts-bounces at lists.febo.com
> A "Discussion of precise time and frequency measurement" time-nuts at lists.febo.com
> Cc "Ulf Kylenfall" ulf_r_k at yahoo.com
> Data Tue, 6 Oct 2020 22:49:30 -0400
> Oggetto Re: [time-nuts] Aging 5065A ?
> 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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