[time-nuts] SR620 question

[Magnus Danielson]

Gerhard,

On 01/27/2015 09:00 PM, Gerhard Hoffmann wrote:
> Hi, fellow time nuts,
>
> I have some questions regarding the Stanford SR620:
>
> 1. Is it a drawback wrt ADEV when a SR620 does not have have the opt. oven
> if I have an ultra clean external reference? Does it use the external
> ref directly
> or does it just pull the own reference to the external value in the long
> run,
> no matter if it's the good or the bad oscilator?

It locks it up with a PLL. See page 9 in PDF below, smack in the middle 
is the input circuit and PLL.

This page also gives you all the hints of how to wire in a better 
oscillator if you wish.

> 2 I have seen that the manual has a parts list and references the circuit
> diagrams, but they are not included in the pdf. Are the circuits somewhere
> out there?

http://www.ko4bb.com/manuals/81.226.54.139/SR620_Universal_Time_Interval_Counter_Schematics.pdf

> My 5370A has become so unreliable that it needs replacement.

What issues do you see?

Cheers,
Magnus