[time-nuts] HP 5065A super

Attila Kinali attila at kinali.ch
Thu Feb 22 08:55:18 EST 2018

On Thu, 22 Feb 2018 07:00:54 -0500
ew via time-nuts <time-nuts at febo.com> wrote:

> Now a step by step work over, including HP mods for later  units like 
> replacing the 74196’s in the synthesizer module with 74LS196. May have been 
> end of life of the 74196.

With some slight change of the circuit, you should be able to replace
the 74196 by an 74163 which is available as LVC and thus should be
around for the next 10-20 years at least.

> Now to the purpose of this post. The A9 module is after 88 a significant 
> change and Corby sees an improvement against his Maser. We are doing a board 
> and maybe some other will be interested.

What does the A9 module do, for those of us who have not learned the inner
workings of the 5065 by heart? "Integrator Assembly" doesn't say too much....

> Here are the issues
> A    is the LT1793 the best choice the time constant is 0.05 seconds with a 
> 10 K resistor and 5 uF Capacitor

What are your constraints? For every single parameter, there is an opamp
that beats the LT1793.
Do you just want to replace the opamp on A9 or build a new A9 from scratch?
If you can live with a power supply <12V, then I'd go for the LTC6240HV.

> B    should we add resistors and decoupling on the + - 15 volt op amp supplies

Depends on the noise of the power supply. My experience is, that resistors
in the power path causes more trouble than not having them. Though, I highly
suspect those were mostly caused by improper design. If you have problem with
noise on the power supply, I would rather suggest to use some low noise
LDOs instead. The TPS7Axx family from TI has quite a few offerings of
suitable LDOs. They are not on par with the LT3042, but they beat anything
you will have in 5065. And they are easier to solder :-)

> C    Gold plating the edge connecter,  does any one know a reasonable source, 
> or is doing it at home an option and if yes, how best way to do so.

There are gold plating solutions available, if you want to do it at home.
Though I would suggest to choose a PCB manufacturer that offers it.
In europe, i'd recommend Eurocircuits, but i'm pretty sure you have a
similarly cheap shop in the US. There are probably some shops in China
that offer that as well. Mind you, gold plating will increase the PCB
cost considerably, as it's a non-standard process. Not to mention that
you need hard gold for connector contacts, which is different from the
standard gold plating you will get as surface finish.

			Attila Kinali
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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