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

Adrian rfnuts at arcor.de
Sat Aug 8 20:35:47 UTC 2009


Magnus,

yes, but there are two Q3 transistors on the same schematic. I think Jim 
is talking about the other Q3 that is in the upper right corner of fig. 
5-12, and is marked 2N1701. It's just there to generate +17.4 (and +7) 
from the +24, and is controled by the +18 V regulator in the oven assy 
(A1A4 outer oven controler).
If the +18 volts read +25, then the +18 regulator would be faulty.

Adrian

Magnus Danielson schrieb:
> 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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