[time-nuts] HP 106B quartz frequency standard...the story so far

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 8 17:58:30 UTC 2009


Jim Palfreyman wrote:
> OK folks, I've rechecked the voltages and here's the details.
> 
> Firstly, changing the oven temperature screw was a mistake. Read a
> previous thread to see why I did it. It was logical given my
> experience with 10811 ovens. I've owned up to it and begged
> forgiveness from the great Flying Spaghetti Monster. It never answered
> so it must have made me do it. Please drop that now. :-)
> 
> When I first powered the unit up it had bad and leaking NiCd batteries
> and made a horrible sound. I removed those and I presume something was
> damaged.
> 
> The "input" voltage to the 2N1701 is normal (according to the front
> panel meter) and is close to 26V. The "output" voltage is 25V and not
> 18V as the manual says. I have the manual now and anyone (with more
> experience than me on old fashioned power supplies) who wants to
> comment I am happy to email the circuit diagram and eagerly await
> comment!!!

Now that I have looked at it and also read the relevant description 
text, all I can conclude is that the circuit actually behaves as 
intended. Just look at the text on battery current limitation, which 
includes a pasus on behaviour when batteries is removed.

The battery charge limiter will actually act as a current limiter to Q1 
so the regulated voltage varies in level accordingly. With no batteries 
installed, it does drift upwards in voltage as a result.

So, the "regulated" voltage is infact designed to vary around. The 
"regulated" aspect of it is damping of the rectified voltage ripple but 
the DC level is allowed to wander around.

If voltage is below 20 V, the relay disconnects so that the batteries 
does not discharge further. Neat.

Cheers,
Magnus




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