[time-nuts] +12 Volts 1A (plus a bit) supply?
Bob Camp
lists at rtty.us
Thu Jun 27 20:27:36 EDT 2013
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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