[time-nuts] +12 Volts 1A (plus a bit) supply?

Bob Stewart bob at evoria.net
Fri Jun 28 00:37:16 UTC 2013


Thanks for the correction Bob.  I don't know what made me think it was an on/off oven.  The OC-050 datasheet gives a drain of 12 watts in warmup and 4 watts in run mode, so I went with that in the post I just made, calculating the loads, etc.

Bob




----- Original Message -----
> From: Bob Camp <lists at rtty.us>
> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Cc: 
> Sent: Thursday, June 27, 2013 7:27 PM
> Subject: Re: [time-nuts] +12 Volts 1A (plus a bit) supply?
> 
> Hi
> 
> The OCXO in the TBolt has a linear controller. It drops back to about 150 to 250 
> ma on the +12 line after warmup. It's been at least 40 years since I saw an 
> on/off oven control in production ….
> 
> Remember that the +12 feeds the oscillator circuit. The more crud on the 12 
> volts, the worse the phase noise of the output. A linear regulator is a good 
> idea.
> 
> Bob
> 
> On Jun 27, 2013, at 3:49 PM, Bob Stewart <bob at evoria.net> wrote:
> 
>>  Hi Hal and other responders,
>> 
>>  I believe that the OCXO uses an ON-OFF type of regulation.  So, no, it 
> doesn't use 1A all the time.  Maybe I should just put an ammeter in the line 
> and see what kind of duty cycle it has after it's at temperature.
>> 
>> 
>>  I tried a 7812 regulator with a small dissipator on it.  It goes into 
> overheat mode almost immediately and the output voltage starts quickly doing 
> down.  The case does have provisions for a single TO-3 transistor conducting 
> heat to the back of the case with no radiating fins.  I had briefly considered 
> using a zener and a 2N3055.
>> 
>>  I think that instead of worrying this to death, I'm just going to use a 
> brick to get it together, and then if something comes up later that I like, 
> I'll put that in.  I did like the looks of that PT5102 but it's at end 
> of life, and 1A is right at it's limit.  I've given some consideration 
> to seeing whether I can pull a few turns off the transformer secondary, as well.
>> 
>> 
>>  Bob - AE6RV
>> 
>> 
>> 
>>  ----- Original Message -----
>>>  From: Hal Murray <hmurray at megapathdsl.net>
>>>  To: Bob Stewart <bob at evoria.net>; Discussion of precise time and 
> frequency measurement <time-nuts at febo.com>
>>>  Cc: hmurray at megapathdsl.net
>>>  Sent: Thursday, June 27, 2013 2:24 PM
>>>  Subject: Re: [time-nuts] +12 Volts 1A (plus a bit) supply?
>>> 
>>> 
>>>  bob at evoria.net said:
>>>>  The transformer gives me about 20 volts DC out.  Dropping 8 volts 
> at 1 amp
>>>>  is just a lot of power to void with a resistor.  I'd like to 
> avoid 
>>>  having
>>>>  that much waste heat in the unit.
>>> 
>>>  Does it really take 1A after it's warmed up?
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