[time-nuts] FRSc RB lamp experiment

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Feb 13 19:01:44 UTC 2011


paul swed wrote:
> Startup circuit looks like a bad op amp used as a comparator. U1 section a.
> This is a LM 158. I have a LM 148 on hand suspect they are different in
> temperature quality. So will look it up and see. This is a common op amp so
> if the 148 does not work for some reason any numbers of more modern ones
> will. Accept one issue its a T08 can. What pin was 8? ;-)
> Regards
>
>    
The LM148 (quad 741) and LM158 (dual opamp) have different input common 
mode ranges, that of the LM158 extends to the negative supply it is also 
rated for a large input differential voltage.
LM158 pin 8 is the positive supply pin.

Bruce
> On Sun, Feb 13, 2011 at 1:24 PM, Magnus Danielson<
> magnus at rubidium.dyndns.org>  wrote:
>
>    
>> Dear Paul,
>>
>>
>> On 13/02/11 18:50, paul swed wrote:
>>
>>      
>>> Magnus it indeed does look very good.
>>>
>>> I have re-assembled the various boards and the system locked up as normal
>>> after the warm up period. I do indeed have a failure in the lamp control
>>> startup crkt.
>>>
>>>        
>> My R&S does not have a startup circuit, so I can't help on that particular
>> detail. I'm sure you will debug it yourself.
>>
>>
>>   The reference after warm up and adjusting the c field is down in the
>>      
>>> 1x10-11
>>> area. Anyhow I adjusted the c field and the systems not fully assembled
>>> nor
>>> has it really been stabilized long enough. Was simply curious so I do not
>>> think this is really a very accurate assessment. Especially since this is
>>> time-nuts territory.
>>>
>>>        
>> At least it proves that you are up and running at least, modulus quirks.
>>
>>
>>   So next steps is to let the unit cook in or maybe I will further assemble
>>      
>>> it
>>> and troubleshoot the startup crkt. Add the unlock counter. (A pedometer
>>> and
>>> opto coupler) and let the system run for a long while perhaps a week or so
>>> to see what really happens.
>>>
>>>        
>> Sounds like a plan.
>>
>>
>>   Thanks for your guidance and help Magnus. Who would have thought there was
>>      
>>> a
>>> recovery technique for FRS-c RB references.
>>>
>>>        
>> Happy to help. Happy to learn of your progress! Happy to hear I contribute.
>>
>>
>> Cheers,
>> Magnus
>>
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>>      
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