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

[J. Forster]

The circuit is so simple and has so few parts, I'd be inclined to unsolder
the transistors and diodes and test them. It should take less than a half
hour with a Pace solder sucker or equivalent.

If there are bad transistors, you could likely bend the leads of a TO-220
part the fit the PCB and add a small heat sink.

-John

============


> 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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