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

[Adrian]

Re-read Jim's posts.

To me it seems clear that he is talking about the 2N1701 Q3 in the upper 
right corner of fig. 5-12.
He mentioned that +18 measures high, around 26V.
So, the problem is NOT in the battery charger circuit.

The purpose of that Q3 is to generate +17.4V (and +7V) from +26V, with 
the base being connected to +18V, thus the emitter voltage of Q3 is +18V 
- 0.6 to - 0.7V.

The +18V regulator circuit is on the lower left of fig 5-8, A1A4 Outer 
Oven Controller. For a circuit description see 4-40 to 4-44.

The +18V feed the AC amplifier (A1A2), the +15V through R14 (might be 
cooked if run at 26V for extended time) and CR2 on the same board, the 
power amplifier (A1A3), the outer oven temperature control circuit 
(decoupled +18V), and the inner oven control cuircuit A1A5.
The 17.4V that are derived from +18V feed the dividers.

Any adjustments make sense only after fixing the +18V supply.

Actually, Q3 might as well be shorted. I would first remove it from the 
circuit to see if the +18V are then correct.
If not, check the voltages at Q9 and Q7 of A1A4. Q9 is mounted on the 
oven housing cover.

Regards,
Adrian

Bruce Griffiths schrieb:
> 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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