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

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Aug 9 03:37:18 UTC 2009


christopher hoover wrote:
> >  The 2N1701 is a general purpose transistor rated at 60V, 2.5A.
>
> I've mentioned this before, but it bears repeating.
>
> If you are having trouble with an old school linear power supply, in
> many cases you can replace the TO-220 PNP pass transistor *and* the
> reguatlor circuit (based on a 723 or whatever) with a modern
> integrated regulator in TO-220 such as an LT1581.  Strip the regular
> board of everything except for the the input and output caps (if they
> are still good) and wire up a pair of resistors to set the voltage.  
> Add a couple of jumpers to complete the circuit.   And then you are
> good to go.
>
> -ch
>
That probably wont work in this case.
The supply is actually an NPN discrete darlington buffered 32V zener
with a current limit transistor to set the battery charging current to
one of 2 values.
With the battery removed the supply output should rise to 32V - 2Vbe - a
diode drop, ie about 29.8V or so.
The series diode is required to isolate the battery from the regulator
output when the main fails.
It should be much quicker and easier to just find suitable transistors.

Bruce





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